Upper Rocky River Local Watershed Plan Preliminary Findings Report

Upper Rocky River Local Watershed Plan Preliminary Findings Report Prepared for NORTH CAROLINA ECOSYSTEM ENHANCEMENT PROGRAM Prepared by February 2005 Upper Rocky River Preliminary Findings Report February 2005 Table of Contents List of Tables ............................................................................................................................. iii List of Figures ............................................................................................................................. iv 1 Introduction........................................................................................................................... 1-1 1.1 1.2 1.3 Background and Purpose of NCWRP Local Watershed Planning ........................................................... 1-1 Major Tasks Conducted by the Watershed Assessment Consultants ....................................................... 1-2 Preliminary Findings Report .................................................................................................................... 1-2 2 Physical Features .................................................................................................................. 2-1 2.1 2.2 2.3 Hydrology and Subwatershed Delineation............................................................................................... 2-1 Geology and Soils .................................................................................................................................... 2-6 Land Use and Land Cover........................................................................................................................ 2-8 3 Preliminary Functional Assessment ..................................................................................... 3-1 3.1 3.2 3.3 3.4 3.5 Stream Classifications/Use Support Ratings ............................................................................................ 3-1 Overview of Water Quality and Biological Data ..................................................................................... 3-5 Assessment of Aquatic Habitat Functions...............................................................................................3-12 Water Quality Functional Assessment ....................................................................................................3-13 Tetra Tech Preliminary Reconnaissance .................................................................................................3-13 4 Additional Assessment Information ..................................................................................... 4-1 4.1 Land Use and Land Cover Distribution ................................................................................................... 4-1 4.1.1 NLCD Land Use.............................................................................................................................. 4-1 4.1.2 Land Use Distribution and Percent Forest Cover Disturbance by HUC.......................................... 4-2 4.1.3 Impervious Area Coverage.............................................................................................................. 4-5 4.1.4 Sewer Service Areas........................................................................................................................ 4-7 4.1.5 Agriculture ...................................................................................................................................... 4-7 4.2 GWLF Watershed Model and Preliminary Results.................................................................................. 4-8 4.3 Existing Buffer Disturbance Analysis.....................................................................................................4-13 4.4 Reach-Level Bank Erosion Risk Analysis ..............................................................................................4-15 4.5 Assessment of Terrestrial Habitat Functions and Preservation Potential ................................................4-17 4.5.1 Purpose of Habitat and Preservation Potential Assessment............................................................4-17 4.5.2 Terrestrial Habitat Assessment Metrics..........................................................................................4-18 4.5.3 Terrestrial Habitat Scoring Methods ..............................................................................................4-27 4.5.4 Results of Terrestrial Habitat Assessment and Targeting of Preservation Efforts..........................4-27 5 Summary of Land Use Planning........................................................................................... 5-1 5.1 Current Regulations and Land Development Vision for the Watershed ................................................. 5-1 5.2 Implications for Terrestrial Habitat and Water Quality............................................................................ 5-2 5.2.1 Terrestrial Habitat............................................................................................................................ 5-2 5.2.2 Stream Erosion ................................................................................................................................ 5-7 5.2.3 Upland Sediment Loading............................................................................................................... 5-7 5.2.4 Phosphorus Loading .......................................................................................................................5-10 6 Prioritizing Functional Stressors and Areas for Detailed Assessment ................................. 6-1 6.1 Primary Threats to Watershed Functions and Objectives for Detailed Assessment................................. 6-1 6.1.1 Upland Runoff and Riparian Condition........................................................................................... 6-2 i Upper Rocky River Preliminary Findings Report February 2005 6.1.2 Nutrient Loading to Area Streams and the Rocky River Reservoir................................................. 6-3 6.1.3 Upland Sediment Delivery .............................................................................................................. 6-4 6.2 Prioritizing Subwatersheds for Detailed Assessment of Restoration Needs ............................................ 6-4 6.3 Preparing for Detailed Assessment of Preservation Opportunities .......................................................... 6-9 7 Indicators and Assessment Tools.......................................................................................... 7-1 7.1 7.2 7.3 Instream Stressors of Hydrologic and Aquatic Habitat Functions ........................................................... 7-1 Nutrient Loading and Eutrophication Stressors of Water Quality and Habitat Functions........................ 7-6 Riparian Corridor Stressors of Hydrology and Water Quality Functions ................................................ 7-6 8 Additional Data Needs.......................................................................................................... 8-1 8.1 Monitoring Data Requirements................................................................................................................ 8-1 8.1.1 Water Quality Parameters................................................................................................................ 8-3 8.1.2 Stream Channel Geomorphology and Benthic Habitat Data Requirements .................................... 8-4 8.2 Modeling Data Requirements................................................................................................................... 8-4 9 References ........................................................................................................................... 9-1 10 Appendices ......................................................................................................................... 10-1 Appendix A. Appendix B. Appendix C. Appendix D. Appendix E. Appendix F. Rocky River GIS Catalog............................................................................................................A-1 Rocky River Imperviousness Estimation ....................................................................................B-1 GWLF Watershed Model Development .....................................................................................C-1 Summary of Existing Water Quality Data ..................................................................................D-1 Water Quality Monitoring Plan................................................................................................... E-1 Modeling Results and Rankings.................................................................................................. F-1 ii Upper Rocky River Preliminary Findings Report February 2005 List of Tables Table 2-1. Table 3-1. Table 3-2. Table 3-3. Table 3-4. Table 3-5. Table 4-1. Table 4-2. Table 4-3. Table 4-4. Table 4-5. Table 4-6. Table 4-7. Table 6-1. Table 6-2. Table 6-3. Table 8-1. Table 8-2. Percentage of Land Cover Type for Each 14-Digit Hydrologic Unit .................................2-8 Stream Segments Listed on the NCDWQ 303(d) List as Impaired Waters ........................3-4 Ambient Data for Rocky River Upstream (B5950000) and Downstream (B5980000) of the Siler City WWTP – April 2000-August 2003* ....................................3-8 Rocky River Reservoir NCTSI Data...................................................................................3-9 Bioclassification Data for the Rocky River Study Area ...................................................3-11 NCIBI, Rocky River Watershed, Chatham County ..........................................................3-12 Interpretation of Residential Land Use from Census Housing Units..................................4-2 Final Land Use Distribution by HUC (percent) ..................................................................4-3 Land Uses and Estimated Impervious Percentages.............................................................4-7 Summary of Indicators and Tools Used for Preliminary Assessment of Terrestrial Habitat Functions and Preservation Potential ...................................................................4-17 Scoring System for Terrestrial Habitat Preservation Potential .........................................4-27 Terrestrial Habitat Metrics for the Rocky River LWP Subwatersheds .............................4-28 Terrestrial Habitat Priority Scores for the Rocky River LWP Subwatersheds .................4-29 Relationship Between Watershed Functions and Stressors for the Upper Rocky River Study Area ..........................................................................................6-1 Scoring System Used to Rank Subwatersheds for Restoration Priority..............................6-5 LWP Subwatersheds Scoring Results .................................................................................6-8 A Summary of Proposed Stations of Additional Water Quality Monitoring Including Several Established NCDWQ Stations ...............................................................................8-2 Recommended Water Quality Parameters for Additional Monitoring ...............................8-3 iii Upper Rocky River Preliminary Findings Report February 2005 List of Figures Figure 2-1. Figure 2-2. Figure 2-3. Figure 2-4. Figure 2-5. Figure 2-6. Deep River Watershed with Rocky River LWP Study Area Highlighted ..........................2-2 LWP Subwatersheds within the Upper Rocky River HU ...................................................2-3 LWP Subwatersheds within the Middle Rocky River HU..................................................2-4 LWP Subwatersheds within the Bear Creek HU ................................................................2-5 Soil Erodibility in the Rocky River Study Area..................................................................2-7 National Land Cover Dataset Land Use Information for the Rocky River Study Area (USGS, 1992)......................................................................................................................2-9 Figure 3-1. NCDWQ Stream Use Classifications and 303(d) Listed Stream Segments........................3-3 Figure 3-2. Water Quality and Biological Monitoring Sites within the Rocky River LWP ..................3-6 Figure 3-3. Sites Evaluated for Initial Visual Reconnaissance of the LWP Study Area .....................3-15 Figure 3-4. Observed Stream Degradation from Cattle Access and Lost Riparian Vegetation on UT to Nick Creek .........................................................................................................3-16 Figure 3-5. Cattle Observed in Varnell Creek at Arthur Teague Road During Initial Visual Reconnaissance .................................................................................................................3-16 Figure 3-6. Segment of UT to Loves Creek Draining Urban Areas of Siler City................................3-17 Figure 4-1. Distribution of Land Uses Across the Rocky River 14-digit Hydrologic Units..................4-4 Figure 4-2. Impervious Percentages by Subwatershed ..........................................................................4-6 Figure 4-3. Average Annual Total Phosphorus Loading Rates by Subwatershed ...............................4-10 Figure 4-4. Average Annual Total Nitrogen Loading Rates by Subwatershed ...................................4-11 Figure 4-5. Average Annual Upland Erosion Loading Rates by Subwatershed..................................4-12 Figure 4-6. Existing Buffer Disturbance in the Study Area.................................................................4-14 Figure 4-7. Stream Reach Bank Erosion Risk Categories ...................................................................4-16 Figure 4-8. NCGAP Vegetation Alliance Data for Rocky River LWP Study Area ............................4-19 Figure 4-9. Significant Natural Heritage Areas and Natural Heritage Element Occurrences..............4-25 Figure 4-10. Terrestrial Habitat Priority Scores for Rocky River LWP Subwatersheds .......................4-31 Figure 5-1. Chatham County Planning Jurisdiction within the Rocky River Study Area .....................5-3 Figure 5-2. Siler City Planning Jurisdiction and Buffer Requirements .................................................5-4 Figure 5-3. High Quality Habitat Areas Threatened in Future Rural/Agricultural Areas......................5-5 Figure 5-4. High Quality Habitat Areas Threatened in Future Urban Areas .........................................5-6 Figure 5-5. Relationship Between Upload Sediment Erosion and Soil Erodibility Factor....................5-8 Figure 5-6. Bank Erosion and Sediment Threats to Subwatersheds ......................................................5-9 Figure 5-7. Subwatersheds with Elevated Levels of Phosphorus Loading..........................................5-11 Figure 6-1. Urban vs. Rural LWP Subwatersheds .................................................................................6-6 Figure 6-2. Targeted LWP Subwatersheds for Restoration and Management.....................................6-11 Figure 7-1. Field Site Locations within Targeted Subwatersheds for Preservation Opportunities........7-4 Figure 7-2. Field Site Locations within Targeted Subwatersheds for Restoration and Management....7-5 iv Upper Rocky River Preliminary Findings Report February 2005 1 Introduction 1.1 BACKGROUND AND PURPOSE OF NCWRP LOCAL WATERSHED PLANNING The N.C. Ecosystem Enhancement Program (NCEEP) has initiated comprehensive watershed planning efforts in certain high-priority local watersheds in order to meet the following primary objectives: 1) Assessment of historical and current watershed conditions; 2) Identification of the major causes and sources of watershed degradation (including water quality impairment, aquatic habitat degradation, and flooding problems); 3) Involvement of local resource professionals in determining major watershed issues and high-priority focus areas; 4) Prediction of future watershed conditions under alternative land use and watershed management scenarios; 5) Development of a consensus-based package of watershed restoration and protection recommendations, including: a. identification of restoration, enhancement, and preservation opportunities; b. assisting the N.C. Department of Transportation (NCDOT) in meeting future compensatory mitigation needs for stream, riparian buffer and wetland impacts; c. identification of non-traditional mitigation projects (e.g., stormwater Best Management Practices (BMPs), urban retrofits, and agricultural practices) for targeted sites or subwatersheds; and d. identification of a long-term follow-up strategy to implement specific watershed protection measures developed during the planning process. The NCEEP selected the Upper Rocky River watersheds (consisting of three 14-digit Hydrologic Units) as high-priority areas for watershed planning due to two primary factors: (1) documented water quality and aquatic habitat problems in selected stream segments, including segments listed on the 2004 Clean Water Act Section 303(d) list of impaired waters submitted to the U.S. Environmental Protection Agency; and (2) ongoing threats to local watershed health which may be attributed to impacts from urban/suburban development, clearing of riparian buffers, agricultural activities, and/or other nonpoint sources. The NCEEP Local Watershed Planning (LWP) efforts are moving toward a watershed assessment approach that emphasizes lost or impaired (and restorable) functions of key watershed components (streams, riparian buffers, wetlands, and contributing uplands) within the context of an integrated landscape or ecosystem approach. These functions generally fall into three primary categories: water quality, habitat (both aquatic and terrestrial), and hydrology. These three functional areas are often the focus of watershed assessment and restoration efforts associated with the LWP process. The NCEEP has funding to implement specific restoration, enhancement and preservation projects that may receive compensatory mitigation credit. For identified watershed solutions that are not traditional mitigation projects (e.g., stormwater BMPs), NCEEP is seeking to work with local governments (and other agencies or non-profit groups) to fund such projects under purview of “flexible mitigation” guidelines provided by pertinent regulatory agencies. As part of the development of LWPs, the NCEEP and its consultants work with local stakeholders and/or resource agency professionals, including the formation of a technical advisory committee, to recommend politically and financially feasible watershed solutions, including assistance in identifying possible funding sources for the recommended solutions. 1-1 1-1 Upper Rocky River Preliminary Findings Report February 2005 1.2 MAJOR TASKS CONDUCTED BY THE WATERSHED ASSESSMENT CONSULTANTS The NCEEP has retained Tetra Tech to conduct a technical assessment of watershed conditions within the LWP study area of the Upper Rocky River Hydrologic Units and to provide other support services in the development of the final LWP for the study area. Tetra Tech’s support services to the NCEEP for this LWP effort began in December of 2003 and are scheduled to be conducted in three phases as follows: Phase 1 – Watershed Characterization Phase 2 – Detailed Assessment including Modeling, Field Work, Sampling, and Stakeholder Involvement Phase 3 – Identification of Specific Solutions The first phase of these services, which includes this report, is scheduled for completion by October of 2004. The major deliverables for Phase 1 of Tetra Tech’s watershed assessment work and the key elements of each are outlined below: Preliminary Findings Report including: • Review and Summary of Existing Assessment Information • Review and Summary of Zoning and Planning Information • Subwatershed Delineation • Preliminary GIS Analysis of LWP Study Area, including imperviousness and riparian buffer assessment, characterization of land cover and soils, and terrestrial habitat evaluation • Pollutant Load Modeling for Upland Sediments and Nutrients • Data Gathering, Data Review and Identification of Missing Data • Establishment of Watershed Planning Goals and Objectives • Establishment of Indicators and Targets • Selection/Refinement of Assessment Techniques • Identification of Additional Monitoring and Modeling Data Requirements. • Scoping for Phase 2 to prepare for Detailed Watershed Assessment. 1.3 PRELIMINARY FINDINGS REPORT The purpose of this Preliminary Findings Report is to summarize pertinent and readily available sources of information from previous assessment efforts, including the knowledge and input of local resource professionals recruited within the Upper Rocky River HUs. Based on that information, the report will identify potential key indicators of overall watershed integrity, including water quality, which will be used in a future detailed assessment phase of the LWP process. Delineation of subwatersheds within the Upper Rocky River Hydrologic Units will be presented in this report, and throughout the report these distinct subwatersheds will be utilized to assess and characterize portions of the LWP study area in terms of the primary threats to watershed functions within them. A variety of preliminary assessment information, including analyses of imperviousness (Section 4.1.3), disturbed land cover (Section 4.1.2), and riparian corridor condition (Section 4.3) will be presented. In addition, the most recent information from local planning jurisdictions and natural resource agencies pertinent to the study area will also be summarized in this report. The report will end with recommendations regarding the Phase 2 Detailed Assessment portion of the LWP process. 1-2 1-2 Upper Rocky River Preliminary Findings Report February 2005 2 Physical Features 2.1 HYDROLOGY AND SUBWATERSHED DELINEATION The Rocky River LWP study area, shown in the context of Cataloging Unit 03030003 (the Deep River watershed of the upper Cape Fear River basin) in Figure 2-1, is about 177 square miles. The study area encompasses three 14-digit Hydrologic Units (HUs 03030003070010, 03030003070020, and 03030003070050). These HUs will be referred to as the Upper Rocky River HU, the Middle Rocky River HU and the Bear Creek HU, respectively. The GIS data used for the preliminary characterization of the study are is located in Appendix A. The study area comprises a major portion of the upper Rocky River mainstem and the watersheds of several major tributaries including the North Prong Rocky River, Greenbrier Creek, Nick Creek, Loves Creek, Varnell Creek, Meadow Creek and Tick Creek. The study area also includes the entire Bear Creek watershed, but skips the section of the Rocky River proper between Tick and Bear Creeks. The upper Rocky River watershed originates in northeastern Randolph County and southwestern Alamance County, and then trends south-southeast through western Chatham County. Approximately 90 percent of the study area is located in western Chatham. Two impoundments located along the Rocky River within the LWP study area serve as the drinking water supply for Siler City and some surrounding unincorporated rural communities. The upstream impoundment, known as the Rocky River Reservoir, is located on the Rocky River approximately four miles due north of Siler City and is the principal storage reservoir for the water supply. Water is released from the upper reservoir and flows down the river to a drinking water intake located in a small run-ofriver impoundment approximately 1.7 miles due north of town. The location of the water intake is at the downstream boundary of the uppermost Rocky River 14-digit HU (03030003070010), so the HU and the water supply watershed are entirely coincident. Siler City is currently undertaking efforts to expand the capacity of the lower reservoir. The expansion will move the intake only 100 feet downstream, so there will be no significant change in the extent of the water supply watershed boundaries. For purposes of this Local Watershed Planning process, the Rocky River LWP study area was delineated into 50 separate LWP subwatersheds. The subwatersheds were chosen to represent each major tributary and to divide the upper Rocky River watershed into similar-sized drainage areas and areas of similar land use/land cover distribution. The uppermost Rocky River HU, which comprises the water supply watershed, was divided into 14 LWP subwatersheds. The middle Rocky River HU was divided into 22 LWP subwatersheds and the Bear Creek HU was divided into 14 LWP subwatersheds. The delineated subwatersheds are shown in Figure 2-2 through Figure 2-4 by their respective HUs, and generally range in size from about one to three square miles (Table 4-2). 2-1 Upper Rocky River Preliminary Findings Report February 2005 I-40 Greensboro LEGEND 14-digit HU Boundaries County Boundaries Major Highways Rivers and Streams Waterbodies Municipalities Deep River Watershed Rocky River LWP Study Area NC- FORSYTH Jamestown High Point 5 I-8 GUILFORD I-8 5 NC-62 Pleasant Garden US-220 p De e er R iv Archdale US -4 21 22 ALAMANCE Liberty M ud Li ck C ree k Randleman Staley 21 -4 US Mu d Asheboro Lc ik Cr ee k -31 US 1 y ck Ro r ve Ri US-64 Ramseur Deep Siler City N NC-42 CHATHAM 2 -90 NC k Cree Tick Ro ck y Riv er NC-87 SCALE 5 0 5 Miles Seagrove For kC r ee k NC-42 BeaNC-705 rC ree k Deep River Sanford Star Ca bi Biscoe n k Cre e Robbins MOORE Carthage MONTGOMERY Figure 2-1. Deep River Watershed with Rocky River LWP Study Area Highlighted D RANDOLPH -2 NC 2 Goldston ee p Bear Creek Ri ve r r Rive 2-2 Upper Rocky River Preliminary Findings Report February 2005 N North Prong Headwaters UR06 Upper Greenbriar Creek UR08 0 1 2 3 Miles Liberty UR01 49 NC SCALE ALAMANCE Middle North Liberty South UR02 Prong UR07 Rocky River Reservoir UR10 Lower Greenbriar Creek UR09 Johnson Creek UR12 Mud Lick Creek UR11 Rocky River Head waters RANDOLPH Rocky River at Staley UR03 Piney Grove Church UR05 CHATHAM Rocky River Reservoir Staley Staley South UR04 Upper Rocky River Mouth UR14 Lacy Creek UR13 US 42 1 Legend 14-digit HUCs Subwatersheds County Boundaries Perennial Streams Intermittent Streams Major Roads Roads Waterbodies Municipalities National Wetlands Inventory Wetlands Parks and Open Space Figure 2-2. LWP Subwatersheds within the Upper Rocky River HU 2-3 Upper Rocky River Preliminary Findings Report February 2005 LEGEND 14-digit HUC Subwatersheds County Boundaries Perennial Streams Intermittent Streams Major Roads Roads National Wetland Inventory Wetlands Municipalities Waterbodies Nick Creek MR02 CHATHAM Rufus Brewer MR03 Middle Rocky River 2 MR05 SCALE 0 1 2 3 Miles Middle Rocky River 1 MR01 Upper Varnell Creek MR10 N Siler City North MR04 Central Siler City Middle Varnell Creek MR11 Lower Varnell Creek Middle Rocky River 3 MR12 Middle Rocky River 4 MR13 US 64 US 421 MR07 Lower Loves Creek MR08 MR09 Siler City Upper Loves Creek MR06 Upper Meadow Creek MR14 Middle Rocky River 5 MR16 Welch Creek MR19 Lower Meadow Creek MR15 Middle Tick Creek 2 MR21 MR22 Lower Tick Creek Tick Creek Tributary MR18 Upper Tick Creek MR17 Middle Tick Creek 1 MR20 Figure 2-3. LWP Subwatersheds within the Middle Rocky River HU 2-4 Upper Rocky River Preliminary Findings Report February 2005 Upper Little Bear Cr eek BC10 Harts Creek BC14 Lower Bear Creek BC13 Middle Bear Cr eek 3 BC12 US 42 Bear Cr eek Tributary 4 BC05 Upper Bear Creek BC01 Bear Cr eek Tributary 3 BC04 Sandy Branch BC08 Bear Creek Tributary 5 BC06 1 Lower Little Bear Cr eek BC11 Middle Bear Creek 2 BC09 Middle Bear Cr eek 1 Bear Cr eek Tributary 1 BC02 Bear Cr eek Tributary 2 BC03 N C 90 BC07 2 LEGEND N 14-digit HUC Subwatersheds County Boundaries Perennial Streams Intermittent Streams Major Roads Roads National Wetland Inventory Wetlands Municipalities Waterbodies 2 0 2 Miles Figure 2-4. LWP Subwatersheds within the Bear Creek HU 2-5 Upper Rocky River Preliminary Findings Report February 2005 2.2 GEOLOGY AND SOILS The Rocky River study area lies within the Carolina Slate Belt and is typically characterized by well drained, moderately permeable soils formed from a variety of igneous and metamorphic rock. The majority of the study area is within Chatham County, NC, where a county-level GIS soil survey is not currently available. However, the State Soil Geographic Database (STATSGO) for North Carolina has information about the dominant soil series found within the study area (Figure 2-5). Soils are mapped according to their soil erodibility factors, the primary soil property used for erosion modeling. The STATSGO database indicates that the dominant soil series in the northern (Rocky River headwater) portion of the study area includes Hiawassee clay loam, Cecil sandy loam, Herndon silt loam and Helena sandy loam. In the Tick Creek and Loves Creek watersheds, the dominant soil series are Wedowee sandy loam and Varina loam sand. In the Bear Creek watershed, the dominant soils are shallow silt loams in the Goldston and Badin series. A majority of these soils are classified as hydrologic group B and range in depth from 10 to 60 inches. Soils in the Bear Creek watersheds are primarily in hydrologic group C, with depth to weathered bedrock typically less than 17 inches. Hydrologic soil groups are a NRCS classification based on the soil’s runoff potential, ranging from A to D, with hydrologic group A having the smallest runoff potential and D having the greatest. In general, soils in the Rocky River watershed north of U.S. Highway 64 have soil erodibility factors (K) above 0.26 and are more susceptible to erosion than soils in the southern areas where K values are generally at or below 0.21. Based on the above comparison, the northern portions of the study area tend to have more deep, permeable, and erodible soils. In contrast, the southern portions of the study areas have soils that are shallow and impermeable, though relatively resistant to inter-rill (sheet flow) erosion. 2-6 Upper Rocky River Preliminary Findings Report February 2005 Upper Rocky River US Hi gh Ro y ck 42 1 wa y ek Cre nell Var es ov L Middle Rocky River C Tic k k ree ve Ri ek re C r US Highway 64 N Bear Creek N C H hw ig ay 2 90 k ree rC a Be 2 0 2 4 Miles 14-digit Hydrologic Units Streams Major Roads Soil Erodibility Factor Weighted .13 .21 .26 .28 .34 Figure 2-5. Soil Erodibility in the Rocky River Study Area 2-7 Upper Rocky River Preliminary Findings Report February 2005 2.3 LAND USE AND LAND COVER Approximately 89 percent of the study area is within Chatham County, including the Town of Siler City and most of the Town of Liberty and the Town of Staley. Five percent of the study area extends into southwestern Alamance County, and six percent extends into northeastern Randolph County. A preliminary GIS analysis of the land cover data was performed using 1992 National Land Cover Data (NLCD). A description of the NLCD dataset can be found in Section 4.1.1. This data is summarized by 14-digit hydrologic units and presented in Table 2-1. About 65 percent of the entire study area is classified as forest and wetland, about 2.5 percent is developed or disturbed, 31 percent is in agricultural uses (cropland and pasture) and 1 percent is open water. A detailed map of NLCD land use distribution is presented in Figure 2-6. A more comprehensive description of land use and methods used for updating the coverage within the study area is presented in Section 4-1. Table 2-1. Percentage of Land Cover Type for Each 14-Digit Hydrologic Unit Area (sq mi) Water 54.2 70.9 51.8 176.9 1.5% 1.0% 0.9% HU Name Upper Rocky River Middle Rocky River Bear Creek Total HU Number 03030003070010 03030003070020 03030003070050 Urban 2.6% 3.7% 0.6% Barren 0.0% 0.1% 0.0% Forest 54.2% 65.7% 68.8% Ag. 39.1% 27.7% 27.0% Wetland 2.5% 2.0% 2.6% 1.1% 2.5% 0.0% 63.1% 31.0% 2.3% 2-8 Upper Rocky River Preliminary Findings Report February 2005 Figure 2-6. National Land Cover Dataset Land Use Information for the Rocky River Study Area (USGS, 1992) 2-9 Upper Rocky River Preliminary Findings Report February 2005 (This page left intentionally blank.) 2-10 Upper Rocky River Preliminary Findings Report February 2005 3 Preliminary Functional Assessment 3.1 STREAM CLASSIFICATIONS/USE SUPPORT RATINGS Rules contained in Section 15A NCAC 02B.0200 of the North Carolina Administrative Code describe a classification system by which the North Carolina Environmental Management Commission (EMC) and the North Carolina Division of Water Quality (DWQ) are to assign use classifications to waterbodies across the state. These use classifications stipulate the specific best uses for each waterbody and determine the standards to which water quality is to be protected in order to maintain those uses. For more information on the NCDWQ’s use support classifications for surface waters (and associated water quality standards), refer to http://h2o.enr.state.nc.us/admin/rules/. Figure 3-1 shows the current classification of perennial streams within the study area. Stream segments in the headwater areas of the Rocky River (those above the Rocky River Reservoir) are classified as Water Supply-III (WS-III), which indicates waters protected as water supplies within low to moderately developed areas. The best usage of these waters is defined as a “source of water supply for drinking, culinary, or food-processing purposes for those users where a more protective WS-I and WS-II classification is not feasible and any other best usage specified for Class C waters.” In addition to the WS-III classification, the segment of the Rocky River from a point 0.3 miles downstream of Lacy’s Creek to the dam at the lower water supply for Siler City carries a sub-classification CA. Waters within a critical area (CA) are protected by more stringent restrictions on development compared to waters outside the critical area. All remaining perennial stream segments in the study area are Class C waters. The best uses assigned to Class C waters are “aquatic life propagation and maintenance of biological integrity (including fishing and fish), wildlife, secondary recreation, agriculture, and any other usage except for primary recreation.” The Class C designation is the minimum standard for all freshwaters in North Carolina. Several stream segments within the study area are included on the North Carolina 2004 Impaired Waters List (303(d) List – http://h2o.enr.state.nc.us/mtu/download.html). These segments include the main stem of the Rocky River from its source to the Rocky River Reservoir and the entire length of Love’s Creek (Figure 3-1). Table 3-1 provides the description for each segment with the associated details from the 303(d) List. Section 305(b) of the Clean Water Act requires that states periodically evaluate each waterbody, and based on available data, determine whether water quality within the waterbody is adequate to support its designated uses. In North Carolina, use support for a particular basin is evaluated every five years in conjunction with the development of basinwide plans. Per the 305(b) requirement, NCDWQ reports on waterbodies across the state every two years and assigns use support ratings to each indicating whether they are “Supporting” or “Impaired” for their designated uses, based on updated information from the basin plans. Waters with inconclusive data are listed as “Not Rated” and waterbodies lacking data are listed as “No Data.” Section 303(d) of the Clean Water Act requires that states place waters that are rated “Impaired” on a list of Impaired Waters, referred to as the 303(d) List. Section 303(d) also requires that a Total Maximum Daily Load (TMDL) be determined for any waterbody that is impaired by a specific identifiable pollutant or pollutants. The intent of the TMDL is to identify sources for the specific pollutant(s) and reduce the pollutant loads from those sources to the extent necessary to improve water quality to a level that will restore the uses deemed impaired. NCDWQ makes a concerted effort to consider all sources of data when determining the use support status of a given segment or portion of a waterbody. However, often no ambient water quality monitoring station is located within the area to be rated and no special studies have been performed there. NCDWQ is sometimes left to rely on a limited amount of biological monitoring data to make judgments regarding 3-1 Upper Rocky River Preliminary Findings Report February 2005 use support. Typically, NCDWQ conducts widespread biological monitoring across each river basin within the state every five years as part of the basinwide management planning cycle. The 2002 305(b) Report and 303(d) List are available for download from NCDWQ at http://h2o.enr.state.nc.us/wqs/, as is the 2004 Cape Fear Basin-Wide Assessment Report. The Draft 2004 Integrated 305(b) and 303(d) Report has recently become available from NCDWQ for public review and comment, and the draft reflects no changes in the impaired listing status of either creek in the Rocky River watershed. The 2004 draft is now available for download on the NCDWQ website at http://h2o.enr.state.nc.us/tmdl/General_303d.htm. 3-2 Upper Rocky River Preliminary Findings Report February 2005 No 9 Liberty r th y4 Hw P ng ro R oc reek br iar C Green r Upper Rocky River ek re C k ee Staley Ro ck yR ky R ive iv e r US Hw y4 M ud ck Li ick N 21 Cr ree k rne Siler City Cr ee k Va ll C Middle Rocky River R ock US Hwy 64 Lo v es R ive r Meadow Cree k y r ee k ck C Ti N Bear Creek Hart s Creek n Sa B dy k ree ar C Be Bea r Cre ek y Hw 2 90 ran ch 0 1 2 3 Miles Study Area 14-digit Hydrologic Units Major Roads Municipal Boundaries DWQ Use Classification C WS-III WS-III CA 303d Listed Segments (NCDENR 2004) Figure 3-1. NCDWQ Stream Use Classifications and 303(d) Listed Stream Segments 3-3 Upper Rocky River Preliminary Findings Report Table 3-1. Stream Segments Listed on the NCDWQ 303(d) List as Impaired Waters Assessment Unit (AU) Class Subbasin Impaired Use Year Listed Category Reason for Listing February 2005 Waterbody and Description Potential Source(s) Miles Rocky River From source to Rocky River Reservoir 17-43-(1)a WS-III 30612 Overall 2000 6 Impaired biological integrity: Stressors not identified 1. 2. Agriculture Pasture GrazingRiparian and/or Upland 10.6 Loves Creek From source to US 421 From US 421 to Siler City WWTP From Siler City WWTP to Rocky River 17-43-10a 17-43-10b 17-43-10c C C C 30612 30612 30612 Overall Overall Overall 1998 1998 1998 6 6 6 Impaired biological integrity: Stressor study complete Impaired biological integrity: Stressor study complete Impaired biological integrity: stressor study complete 1. 1. 2. Urban Runoff/Storm Sewers Major Municipal Point Source Urban Runoff/Storm Sewers 2.8 0.5 Source: NCDENR (2004) 3.1 3-4 Upper Rocky River Preliminary Findings Report February 2005 3.2 OVERVIEW OF WATER QUALITY AND BIOLOGICAL DATA Water quality monitoring data are available from two sites on the Rocky River and fish community assessments were performed at four sites within the Rocky River LWP study area. Benthic communities, stream habitat, and riparian area conditions were evaluated for nine sites throughout the study area. All sites for which these data are available are shown on the map in Figure 3-2. Additionally, NCDWQ samples the Rocky River Reservoir as part of the Lake Assessment Program. The water quality and biological data available are summarized below. A great deal of this summary of water quality and biological data is drawn from a data report prepared by the NCDWQ Watersheds Assessment Team (NCDENR, 2004), which is presented in Appendix D, and from the 2004 Cape Fear Basinwide Assessment Report (NCDENR, 2004). Several freshwater mussel species proposed for state protection (Alasmidonta undulata, A. varicosa and Strophitus undulatus) have been collected from the Rocky River (NCDWQ, 1999). Water Quality Data NCDWQ maintains an ambient water quality monitoring station (AWQMS) on the Rocky River at NC 902 near Pittsboro (STORET station number B6000000), but this station is not located within the study area. Wastewater discharges include several Chatham County schools and a rest home, which discharge a total of less than 1 MGD (million gallons per day) into the Bear Creek drainage area. The Siler City WWTP is the only major permitted discharger in the study area, with a permitted discharge of 4 MGD to Loves Creek (Permit #NC0026441). The discharge is listed as a potential source for the impaired biological integrity of Loves Creek, according to the DWQ Report. The Upper Cape Fear River Basin Association (UCFRBA) performs monthly water quality monitoring at two sites on the Rocky River within the study area. The site near US 64 (B5980000) is located above Siler City, and the site near SR 2170 is located below the Loves Creek confluence, which receives the discharge from the Siler City WWTP. Data for both sites from April 2000 – August 2003 are summarized in Table 3-3. Conductivity, total phosphorus and nitrate levels were substantially higher at the downstream site, likely reflecting the effect of the point discharge. Elevated levels of aluminum (Al), iron (Fe), manganese (Mn) and zinc (Zn) at the upstream site likely reflect the impact from the Rocky River Reservoir where internal stratification results in the release of these metals from bottom sediments and subsequent discharge downstream. Dissolved oxygen levels were generally adequate at both sites, with concentrations between 4 and 5 mg/L occasionally observed. During a monthly monitoring run in January 2002, division of water quality staff noted water quality problems at the Rocky River at NC 902 (B6000000). Future observations of filamentous algae indicating nutrient rich waters prompted NCDWQ staff to monitor the Rocky River five additional times at each of seven sites from October 2002 to October 2003(Table 3-2). Five of these monitoring sites lie within the Rocky River LWP study area (Figure 3-3). The physical and chemical data collected reflect elevated levels of conductivity, fecal coliform and nutrients (nitrogen and phosphorus) in both the main stem Rocky River and tributaries. Contributing factors identified were agricultural runoff from poultry and cattle operations and some cultivated areas, and runoff and discharges from three main urban areas and industrial enterprises (NCDWQ 2004). 3-5 Upper Rocky River Preliminary Findings Report February 2005 NC -49 r nbria Gree Liberty ALAMANCE RANDOLPH CHATHAM r Staley Upper Rocky River k Cree ck Ro $ re ek y v Ri Siler City sC Ú Ê $ # r $ US Lo ve Middle Rocky River $ 1 -42 k Cree Tick Bear Creek er US-64 Ú Ê ð $ r # $ 2 -9 0 NC N ek r Cre# $ # Bea $ r $ 4 0 4 Miles Rocky River LWP Study Area County Boundaries 14-digit Hydrologic Units Waterbodies # Minor NPDES Dischargers Ambient Water Quality Monitoring Sites Benthic Monitoring Sites Fish Monitoring Sites UCFRBA Monitoring Sites ð $ r # Major NPDES Dischargers Ú Ê Figure 3-2. Water Quality and Biological Monitoring Sites within the Rocky River LWP 3-6 Upper Rocky River Preliminary Findings Report February 2005 Liberty -49 NC ALAMANCE r th No gR on Pr ky oc r nbri a Gree CHATHAM RANDOLPH 2 " 8 k Cree 1 " 8Rocky River Riv er Staley US - 42 1 Ro ck yR ive r Siler City " 8 3 US-64 Lo ve sC re ek " 8 4 k Cre e Tick 21 -4 US 2 90 " 8 6 k Cre e Be ar NC Figure 3-3. Table 3-2. Additional Water Quality Monitoring Sites Additional Water Quality Monitoring Sites from October 2002-October 2003 Waterbody Rocky River North Prong Rocky River Rocky River Tick Creek Rocky River Bear Creek Rocky River Sampling Site 1 2 3 4 5 6 7 Location Staley Snow Camp Rd. (SR 1300) Clyde Clark Rd. (SR 1358) US Hwy 64 at Siler City Reeves Chapel Rd. (SR 2170) NC Hwy 902 Woody Dam Rd. (SR 2156) US Hwy. 15-501 3-7 Upper Rocky River Preliminary Findings Report Table 3-3. February 2005 Ambient Data for Rocky River Upstream (B5950000) and Downstream (B5980000) of the Siler City WWTP – April 2000-August 2003* Upstream Downstream Evaluation Level %< or > EL (N) min 4.4 4.0 5.8 50 <0.50 <1.0 4.0 0.0 0.3 0.4 0.1 190 3.2 860 88 10 mean 19.8 7.7 7.0 106.5 12.0 6.4 84.7 0.1 1.6 0.7 0.2 601 4.6 1,513.3 129.2 37.8 1 max 29.8 13.6 8.3 172 110 62 12,000 0.1 4.7 1.2 0.3 1,700 6.1 3,000 230 260 (N) 62 61 62 62 41 41 41 42 41 43 48 22 22 22 10 22 min 4.0 4.4 5.6 56 <0.40 1.0 7.0 0.0 0.1 0.2 0.1 60 2.1 <50 37.0 10.0 mean 18.9 7.4 7.2 415.5 10.8 7.5 143.41 0.1 6.9 1.0 0.4 345 5.9 861 54.6 25.4 max 27.0 13.0 8.7 1,072 120 75.6 6,800 0.6 23.8 1.7 2.5 1,600 18 2,900 95 220 EL >32 <5 6-8 — >50 >10 >2001 — >10 — >0.05 — >7 >1,000 >200 >50 US 0 8.1 3.23 — 2.4 9.8 — — 0 — 100 — 0 87.5 20 12.5 DS 0 4.9 3.23 — 2.4 9.8 — — 24.4 — 100 — 31.8 31.8 0 4.5 TEMP (°C) DO (mg/L) pH Conductivity (umhos/cm) Turbidity (NTU) TSS (mg/L) Fecal Coliform (no/100ml) NH3 (mg/L) NO2+NO3 (mg/L) TKN (mg/L) TP (mg/L) Al (µg/L) Cu (µg/L) Fe (µg/L) Mn (µg/L) Zn (µg/L) 62 62 62 62 41 41 41 10 10 10 10 8 8 8 5 8 *Evaluation Level (EL) = presented to facilitate review. Measurements should not exceed the range (< or >) indicated by EL. Ranges adapted from NCDWQ, April 2003. US = upstream, DS = downstream. Nickel Mercury, Arsenic, Cadmium, Chromium, and Lead all below the quantitation limit for all samples analyzed. 1 Geometric mean. (NCDWQ, February 2004) 3-8 Upper Rocky River Preliminary Findings Report February 2005 Lake Assessment Program The Rocky River Reservoir is a water supply for the Town of Siler City, and public access to the lake is restricted. Storage capacity was increased in 1988 to 424 million gallons, an increase from 60 million gallons. The enlargement raised the water level by 10 feet. The watershed is primarily agricultural with some pasture immediately adjacent to the lake. The lake was last sampled by DWQ during the summer of 2003, when it was considered hypereutrophic, which indicates nutrient enrichment and is characterized by nuisance algal blooms. Data from 1991 to 2003 are displayed in Table 3-4. According to the DWQ report, the water treatment plant samples the lake at the intake for various water quality parameters including pH, iron, manganese, turbidity, and alkalinity. Measuring alkalinity is important in determining a stream’s ability to neutralize acidic pollution from rainfall or wastewater. The pH of water determines the solubility (amount that can be dissolved in the water) and biological availability (amount that can be utilized by aquatic life) of chemical constituents such as nutrients (e.g., phosphorus, nitrogen, and carbon) and heavy metals. Due to historic elevated levels of iron and manganese, there were several complaints of taste and odor problems. The water treatment plant now treats the raw water for manganese. Turbidity and low dissolved oxygen levels have been observed in the reservoir after rainfall events, but these problems are generally temporary. Table 3-4. Date 08/12/2003 07/09/2003 06/12/2003 08/06/1998 07/08/1998 06/03/1998 07/29/1993 08/01/1991 Rocky River Reservoir NCTSI Data NCTSI 6.0[H] 5.5[H] 5.7[H] No score 3.9[E] 4.1[E] 5.4[H] 4.1[E] TP (mg/L) 0.17 0.16 0.19 0.08 0.07 0.18 0.10 0.10 TON (mg/L) 1.19 1.14 1.06 0.66 0.51 0.46 0.92 0.55 CHLA (ug/L) 30 28 37 n/a 35 15 38 41 SECCHI (m) 0.5 0.7 0.7 0.5 0.4 0.5 0.4 0.7 NCTSI = North Carolina Trophic State Index. [E] = Eutrophic, [H] = Hypereutrophic. TP = Total Phosphorous TON = Total Organic Nitrogen CHLA = chlorophyll-a SECCHI = Secchi depth is a measure of the clarity or turbidity of the water (NCDWQ, February 2004) 3-9 Upper Rocky River Preliminary Findings Report February 2005 Benthic Macroinvertebrate Data Benthic macroinvertebrates are associated with the bottom substrates of rivers and streams. These organisms, primarily insect larvae, reflect both long- and short-term water quality conditions that may indicate fluctuations between water quality sampling periods. The North Carolina Division of Water Quality (NCDWQ) uses aquatic macroinvertebrates as one type of indicator of biological integrity in rivers and streams. Benthic macroinvertebrate samples have been collected from two mainstem Rocky River locations and three tributaries, Loves Creek, Tick Creek and Bear Creek. There are five sampling sites on Loves Creek and one on a tributary, two sites on Tick Creek and three on Bear Creek. Special studies of the Siler City WWTP were conducted in 1989 and 1997. Data are summarized in Table 3-5. During assessments of benthic communities, stream habitat and riparian area conditions were evaluated for each sampling site. This protocol rates the aquatic habitat of the sampled reach by adding the scores of a suite of local habitat factors relevant to macroinvertebrates and fish (NCDWQ, 2004). Habitat ratings are based on a score of 0-100, with a score of 100 reflecting the best habitat. Within the NCDWQ protocol for developing bioclassifications for benthic macroinvertebrate community data, the range of ratings includes Poor, Fair, Good-Fair, Good and Excellent. These bioclassifications are a composite of the EPT (number of mayfly, caddisfly, and stonefly species) and Biotic Index (BI) and primarily reflect the influence of chemical pollutants. The EPT metric is a measure of the number of individuals classified as intolerant species present in the sample. The Biotic Index is a score that summarizes the tolerance data for all species collected (NCDENR 2003a). For more information on sampling methods and calculation of criteria refer to http://www.esb.enr.state.nc.us/BAU.html. Benthic community samples from the Rocky River upstream of the confluence of Loves Creek (US 64) yielded a “Fair” bioclassification in 2003 despite “Good-Fair” ratings in previous years (Figure 3-2). The overall habitat score for this reach of the Rocky River reflects an adequate quality of benthic habitat per DWQ (2004). Samples from the Rocky River downstream of the confluence with Loves Creek (SR 2170) yielded a “Good-Fair” rating for 2003, an improvement over a “Fair” rating the previous year. The habitat score for this reach of the Rocky River decreased from 2002 to 2003, but still reflected adequate quality of benthic habitat. Both Tick Creek stations received “Good-Fair” ratings from their most recent sampling event, and the habitat score at the SR 2120 station reflected adequate benthic habitat quality. Special surveys have been conducted on Loves Creek to assess the effects of the Siler City WWTP discharge. Samples from Loves Creek above the WWTP have always yielded “Fair” bioclassifications, indicating a degraded stream. The habitat score from this reach for 2003 also reflected degraded benthic habitat. Samples from Loves Creek below the WWTP have previously yielded “Poor” bioclassifications, but yielded a “Fair” rating in 2003, which suggests some improvement in water quality. It should be noted that results from a 2002 drought impact study indicated that Slate Belt streams were the slowest to recover, so these results may reflect the effect of the drought. The habitat score for this reach for 2003 reflected adequate quality of benthic habitat. Benthic community samples collected in Bear Creek have not been rated. However, the number of EPT taxa collected has been consistently higher than EPT taxa richness in Loves Creek, and BI values have been lower, indicating a more intact benthic fauna. The most recent habitat score for Bear Creek is also higher than Loves Creek, suggesting a higher quality benthic habitat. 3-10 Upper Rocky River Preliminary Findings Report Table 3-5. Bioclassification Data for the Rocky River Study Area Date 07/22/2003 09/30/2002 070/9/1998 06/27/1997 07/27/1993 08/02/1989 Rocky River, US 64 07/21/2003 07/09/1998 06/27/1997 07/27/1993 08/01/1989 Loves Creek, above WWTP near SR 2203 (Waste Treatment Plant Rd) 06/24/2003 06/27/1997 08/01/1989 Loves Creek, below WWTP near SR 2203 (Waste Treatment Plant Rd) Loves Creek, below Golf Course Loves Creek, 2nd Avenue Loves Creek, SR 1006 (Siler City Glendon Rd) UT Loves Creek, Greensboro Rd. Tick Creek, US 421 06/24/2003 06/27/1997 08/01/1989 06/22/2003 06/23/2003 06/24/2003 06/25/2003 02/1998 07/1993 08/1985 Tick Creek, SR 2120 (Ike Brooks Rd) Bear Creek, SR 2333 (S. Main St) Bear Creek, SR 2189 (Vernie Phillips Rd) Bear Creek, SR 2155 (Mays Chapel Rd) 07/2003 07/1998 08/1991 08/1991 03/2003 07/1990 EPT 15 8 18 19 19 11 15 17 20 12 16 7 8 7 6 4 2 13 7 3 4 18 5 19 20 15 16 15 16 15 BI 5.87 4.87 6.28 6.48 6.54 6.74 6.51 6.42 6.74 6.94 6.73 7.37 7.25 7.5 6.72 7.41 8.41 6.31 7.14 7.63 7.32 4.86 6.57 6.54 6.46 5.93 6.78 6.51 5.05 4.86 EPTBI 4.99 4.87 5.07 5.60 5.38 6.13 5.44 4.63 5.72 5.68 5.81 6.95 6.61 6.85 7.04 6.06 6.62 4.34 6.42 7.10 6.43 4.81 6.57 5.41 5.93 5.93 5.80 5.58 5.05 4.86 February 2005 Site Location Rocky River, SR 2170 (Rives Chapel Ch Rd) Bioclassification Good-Fair Fair Good-Fair Good-Fair Good-Fair Fair Fair Good-Fair Good-Fair Fair Fair Fair Fair Fair Fair Poor Poor Not Rated Fair Not Rated Not Rated Good-Fair Poor Good-Fair Good-Fair Good-Fair Not Rated Not Rated Not Rated Not Rated Habitat 78 84 76 55 78 63 64 70 55 69 85 EPT = Taxa richness of mayfly, stonefly, and caddisfly species. BI = Biotic index. Adapted from NCDWQ 1999, 2003a. *EPTBI = Biotic index for EPT species. UT = Unnamed tributary. Not Rated = Bioclassification not assigned due to low flow conditions and/or low stream width. (NCDWQ, 2004) 3-11 Upper Rocky River Preliminary Findings Report February 2005 Stream Fish Community Assessment (NCIBI) The North Carolina Index of Biological Integrity (NCIBI) was initiated in the early 1990s to assess a stream’s biological integrity through examination of fish community structure and health (NCDWQ, 2001). The scores for 10 metrics are summed to obtain an overall NCIBI score, which determines the bioclassification. The NCIBI is a modification of the Index of Biotic Integrity initially proposed by Karr (1981) and Karr et al. (1986). The method was developed for assessing a stream’s biological integrity by examining the structure and health of its fish community. The scores derived from this index are a measure of the ecological health of the waterbody and may not necessarily directly correlate to water quality. A stream with excellent water quality, but poor to fair habitat would not rate excellent in this index. However, a stream which rates excellent on the NCIBI would be expected to have excellent water quality. Data from four stations within the Rocky River LWP study area are summarized in Table 3-6 and are depicted in Figure 3-2. The Bear Creek station at SR 2187 drains a portion of the southwest corner of Chatham County and is subject to considerable flow variation in the summer. These variable flows are believed to be the primary reason for the variability in NCIBI ratings at this station from 1998-2003. The Loves Creek station (SR 2229) drains much of Siler City south of US 64 and above the Siler City WWTP. The species diversity and fish abundance metrics in 1998 scored high and the number of species of sunfish collected indicated good instream pool habitat. However a decrease in the NCIBI score in 2003 and a “Good-Fair” rating may indicate water quality or habitat degradation in this reach since 1998. The Rocky River station is located above the Rocky River Reservoir and was given a “Good-Fair” NCIBI rating in 1998 and 2003. These scores may be reflective of the effects of nonpoint source runoff and enrichment. Tick Creek had a decline in fish diversity from “Excellent” in 1994 to “Fair” in 2003. Although habitat degradation has been observed where cattle have access to the stream, the reason for the decline is not clear, and the site will be re-sampled by DWQ. Benthic samples at this same site yielded a bioclassification of “Good-Fair” in both 1998 and 2003. Table 3-6. NCIBI, Rocky River Watershed, Chatham County Date 06/13/2003 10/29/1999 04/07/1999 04/23/1998 05/05/2003 05/04/1998 05/05/2003 05/04/1998 06/13/2003 04/19/1994 NCIBI Score 44 36 40 50 44 52 40 44 38 56 NCIBI Rating Good-Fair Fair Good-Fair Good Good-Fair Good Good-Fair Good-Fair Fair Excellent Station, Location Bear Creek, SR 2187 Loves Creek, SR 2229 Rocky River, SR 1300 Tick Creek, US 421 NCIBI = North Carolina Index of Biological Integrity. Adapted from NCDWQ, 1999. (NCDWQ, February 2004) 3.3 ASSESSMENT OF AQUATIC HABITAT FUNCTIONS Aquatic habitat is a place where a plant or animal lives, receiving sufficient food, water, and shelter to survive and reproduce. Based on information presented in Section 3, Appendix D and the 2004 Cape Fear River Basin Basinwide Assessment Report, there are several stream reaches in the study area with significant aquatic habitat functional loss. The best indicators available for aquatic and riparian habitat are the habitat score calculated by DWQ staff during the basinwide assessments of benthic communities and the NCIBI score, which determines the bioclassification. Bioclassifications and habit scores for the Loves 3-12 Upper Rocky River Preliminary Findings Report February 2005 Creek watershed are generally poor when compared to the remainder of the study area. Of the 13 sites surveyed for bioclassifications (Table 3-5), Loves Creek and Tick Creek were the only sites with any historically “Poor” classifications. Loves Creek and Tick Creek also had the lowest habitat scores in the study area, with Loves Creek receiving a 55 (out of 100) at the SR 2203 site. A tributary to Loves Creek also had a habitat score of 55, the lowest score seen in the study area. Tick Creek had a score of 69 at the SR 2120 site, with severe bank erosion and bank trampling from cattle evident. Although Loves Creek had the only “Poor” bioclassification score in the study area, a decline in classifications was seen in the Rocky River at US 64, going from Good-Fair to Fair over the course of five years. Habitat scores were adequate overall for the Rocky River and Bear Creek sites according to DWQ, with productive snags and undercut bank habitat present at the US 64 site for the Rocky River. Section 6 provides the methods and analyses used to determine which subwatersheds have the highest level of degradation within the study area, including the information provided in this section, and the results from the analysis. Section 7 provides information regarding objectives for detailed assessment, which includes the use of habitat assessment field data sheets to be taken into the field, to further quantify and identify aquatic habitat functional losses within the study area. 3.4 WATER QUALITY FUNCTIONAL ASSESSMENT There is limited water quality data available within the study area. The two sites monitored by the UCFRBA on the Rocky River are the only water quality monitoring stations, with some water quality data available for the Rocky River Reservoir through the Lake Assessment Program. The NCIBI scores and benthic data can also be used to interpret water quality conditions. Generally, all monitored sites had acceptable water quality sampling results, with the exceptions being the Rocky River Reservoir with elevated nutrient levels and Loves Creek downstream of Siler City’s WWTP with highly impacted benthic communities. Due to the limited number of water quality monitoring sites in the study area, Section 8.1 makes recommendations for future sampling in the Upper Rocky River watershed. Appendix E provides DWQ’s plans for additional monitoring locations and the parameters to be tested. 3.5 TETRA TECH PRELIMINARY RECONNAISSANCE On February 13, 2004, members of the Tetra Tech project team performed an initial visual survey of the Upper Rocky River Watershed LWP study area. The visual survey had the following purposes: • Familiarize staff with the geography of the study area and characteristics of the major stream systems • Identify and visit many of the monitoring sites for water quality and biological data • Obtain a photographic record of as many sites as feasible within the watershed • Conduct an initial identification of potential problems and restoration opportunities in the study area as input to planning for more detailed analyses. During the survey, approximately 20 individual sites, which are mapped in Figure 3-4, were evaluated. The sites were selected based on the results of the Deep River Cataloging Unit-Wide Restoration Site Search (Tetra Tech, 2003) and all roadway accessible sites which had high or very high risk potential for degradation were visited. During the visual survey, numerous livestock farming operations, particularly cattle and chicken operations, were observed to be located within the study area despite the fact that only two livestock facilities are registered as Concentrated Animal Feeding Operations (CAFOs) with NCDENR (2003) as 3-13 Upper Rocky River Preliminary Findings Report February 2005 of the date of this report. This discrepancy is due to the fact that the livestock farms in western Chatham County are predominantly beef cattle operations with less than the 100 head of cattle that would require CAFO registration, and broiler chicken operations, which utilize dry litter waste management as opposed to wet waste systems that require CAFO registration (Groce, 2004). While the land management practices associated with agriculture are generally fair to good and agricultural BMPs are widely implemented within the study area (Groce, 2004), the potential for adverse impacts to water quality and stream morphology are significant with the level of livestock farming in western Chatham County. Of the 20 sites visited, the conditions in at least six of the streams observed indicated that cattle had unrestricted access to the stream segment and active stream degradation was occurring. At two of those sites, cattle were observed in the stream. Figure 3-5 shows a stream segment within the study area where degradation from cattle access, loss of riparian vegetation, and hoof-shear stream erosion is evident, and Figure 3-6 shows a stream segment where cattle were observed in the stream. During the survey, sites were also visited within the urbanized areas of Siler City. At both sites evaluated on Loves Creek, the stream showed clear degradation from the impacts of urban stormwater runoff and past hydromodification. Active bank erosion, sediment deposition and indications of past channelization were all readily evident in the stream. Figure 3-7 shows a segment of Loves Creek that is fairly indicative of conditions in the stream throughout its predominantly urban subwatershed. 3-14 Upper Rocky River Preliminary Findings Report February 2005 NC 49 N W ek r C re nbria Gree Liberty NC 49 E $ RANDOLPH No rt ( X Staley hP ro ng ( X ( X ( X Ro ck Ro c $ $ $ 2 $ $S SCALE 0 2 Miles y Ri ve r ( X US 42 1 ky Ri ve r CHATHAM ( X LEGEND Major NPDES Discharges Reconnaissance Sites (Registered) Concentrated Animal Feeding Operations County Boundaries Major Roads Roads USGS 1:24,000 Hydrography Perennial Intermittent Open Water NWI Wetlands Municipalities LWP Study Area ( X Siler City $ # S # ( X ( X # r Va ek re ll C ne ( X US 64 $ ck Ro ive yR Cr ee k ( X r Lo ve s ( X ( X k Creek ( ic X T ( X ( X ek ow Cre Me ad $ Ro ck yR i ve r ( X US Harts Creek 1 42 $ $ ( X ( X ( X NC 90 2 r. yB nd Sa r Cre B ea ek Figure 3-4. Sites Evaluated for Initial Visual Reconnaissance of the LWP Study Area 3-15 Upper Rocky River Preliminary Findings Report February 2005 Figure 3-5. Observed Stream Degradation from Cattle Access and Lost Riparian Vegetation on UT to Nick Creek Figure 3-6. Cattle Observed in Varnell Creek at Arthur Teague Road During Initial Visual Reconnaissance 3-16 Upper Rocky River Preliminary Findings Report February 2005 Figure 3-7. Segment of UT to Loves Creek Draining Urban Areas of Siler City 3-17 Upper Rocky River Preliminary Findings Report February 2005 (This page left intentionally blank.) 3-18 Upper Rocky River Preliminary Findings Report February 2005 4 Additional Assessment Information 4.1 LAND USE AND LAND COVER DISTRIBUTION 4.1.1 NLCD Land Use The most recent, comprehensive land cover database available for the entire Rocky River watershed is contained in the National Land Cover Database (NLCD) from the Multi-Resolution Land Characterization (MRLC) Consortium (USGS, 2000). The NLCD is based on interpretation of Landsat satellite thematic mapper imagery. The images were recorded between 1992 and 1994 for North Carolina. The NLCD coverage has a nominal 30-meter resolution. In essence, it is an identification of the predominant land cover (rather than land use) within each 30-m pixel. Data are classified into 21 types of land cover, including numerous forest and agricultural classes. In contrast, the information on developed land is somewhat limited. For residential land, the NLCD identifies two classes: “Low”-Intensity Residential is defined as areas with a mixture of constructed materials or other cover in which constructed materials account for 30-80 percent of the total area, while “High”-Intensity Residential is defined as areas in which constructed materials account for 80-100 percent of the total area. These attributes are made at the 30-m resolution, and so may not accurately reflect the characteristics of actual residential parcels. In addition, suburban residential development with significant tree cover may be missed entirely by the Landsat interpretation and be classified as forest. Given the rapid growth in several locations of the Rocky River watershed (Siler City in particular), many areas have undergone land use conversion in the decade since the NLCD was compiled. Land uses described in the NLCD coverage for the study area were reclassified into 15 aggregate land uses with varying physical and chemical properties. Since NLCD does not differentiate between nonresidential urban land uses, but reports them in one lumped class, Tetra Tech assumed this NLCD class was equally divided between office/light industrial and commercial/heavy industrial land uses. These land uses make up about 2 percent of the Rocky River watershed, so a more in-depth analysis was not deemed necessary. To improve the technical defensibility of load estimates that will be generated using the watershed model, Tetra Tech updated the NLCD coverage by comparing it to the 2000 Census data, which provides an actual count of residences with a more current date. The Census provides, at best, an uncertain estimate of the density of residential land uses, and thus requires use of a translation method to account for these uncertainties. Such a translation method was developed for a modeling study of the Jordan Lake Watershed (Tetra Tech, 2003b) using county tax parcel data for the subset watersheds. A reasonable, empirical translation was developed for residential land areas. The first step was to analyze the residential information from Census blocks, calculate an “apparent” lot size (area of the Census block divided by number of households, which is generally biased high), and sort the parcel counts into categories by this apparent Census lot size, as follows: CRVH CRHH CRMH CRML CRLL < 0.25 acres per dwelling unit 0.25 – 0.5 acres per dwelling unit 0.5 – 1 acres per dwelling unit 1 – 1.5 acres per dwelling unit 1.5 – 2 acres per dwelling unit 4-1 Upper Rocky River Preliminary Findings Report February 2005 CRVL CRR 2-3 acres per dwelling unit > 3 acres per dwelling unit In comparison to areas with parcel data, a reasonable approximation is obtained from the Census counts by minimizing the sum of the squared error in parcel counts, using the empirical relationships shown in Table 4-1. Table 4-1. Interpretation of Residential Land Use from Census Housing Units Code RVH RHH RMH RML RLL RVL Nominal Size 1 (ac per du) 0.077 CRVH + CRHH Number of Units Land Use Name Residential – Very High Density (<0.25 acres per du) Residential – High Density (0.25 – 0.5 acres per du) Residential – Medium High Density (0.5-1 acres per du) Residential – Medium Low Density (1-1.5 acres per du) Residential – Low Density (1.5-2 acres per du) Residential - Very Low Density (>2 acres per du) 1 Not interpreted from Census 0.5 1.5 CRMH + CRML + CRLL + 0.79·CRVL + 0.181·CRR 0.21·CRVL + 0.261·CRR Not interpreted from Census 2.5 0.479·CRR du – dwelling unit The attribution assigns 100 percent of the Census households in all classes except CRR (Residential – Rural), where 92.1 percent of the Census count is assigned. The remaining portion of CRR presumably represents multiple housing units on large rural lots. The two residential classes that are available from the parcel analysis (RHH and RLL) are not interpreted from the Census. Single family RHH is essentially mixed into the RVH and RMH classes due to the failure of the Census to distinguish multi-family and single-family units. RMH is set at the lower-bound acreage to compensate. RML and RLL are essentially predicted as a unit, with area set at the intervening breakpoint. Finally, RVL is predicted as the number of households times 2.5 acres. While many rural lots are larger, the balance of the tract can generally be considered as rural forest or pasture rather than developed land. In any case, the success of the simulation is more dependent on a reasonable estimate of the number of residential units, and thus their imperviousness, than on the total acreage in residential lots. 4.1.2 Land Use Distribution and Percent Forest Cover Disturbance by HUC The final land use database consists of the 1992 NLCD, with residential land uses updated using the 2000 Census. This yields a near-current estimate of land use in the basin, with the primary exception that commercial/industrial development in the Cape Fear basin after the date of the NLCD has not been captured. The distribution of land use by Hydrologic Unit Code (HUC) is provided in Table 4-2 and a visual summary is provided in Figure 4-1. Table 4-3 provides descriptions for the column headings. 4-2 Upper Rocky River Preliminary Findings Report February 2005 Table 4-2. HUC1 BC01 BC02 BC03 BC04 BC05 BC06 BC07 BC08 BC09 BC10 BC11 BC12 BC13 BC14 MR01 MR02 MR03 MR04 MR05 MR06 MR07 MR08 MR09 MR10 MR11 MR12 MR13 MR14 MR15 MR16 MR17 MR18 MR19 MR20 MR21 MR22 UR01 UR02 UR03 UR04 UR05 UR06 UR07 UR08 UR09 Area (mi ) 3.09 1.05 0.89 1.10 1.53 0.96 1.76 1.70 1.17 1.11 1.05 2.20 2.00 1.29 1.10 2.07 0.85 0.90 1.19 1.48 0.86 0.99 0.92 1.68 1.54 0.95 1.03 1.18 1.22 2.30 1.56 1.57 1.23 0.94 1.46 1.66 0.88 1.52 1.22 0.86 1.50 2.28 1.81 1.90 1.70 2 Final Land Use Distribution by HUC (percent) RES 3.23% 3.84% 5.69% 5.90% 4.40% 11.71% 5.97% 7.44% 5.21% 6.00% 7.75% 5.00% 3.74% 3.68% 11.87% 4.94% 5.89% 32.82% 6.22% 16.73% 61.20% 33.69% 6.74% 2.91% 3.50% 7.05% 2.16% 3.91% 1.93% 1.33% 6.67% 3.13% 7.01% 7.46% 5.59% 3.76% 14.52% 11.45% 7.92% 6.09% 4.45% 18.55% 3.76% 3.55% 4.46% COM 0.06% 0.12% 0.56% 0.04% 0.20% 1.56% 0.21% 0.37% 0.07% 0.06% 0.03% 0.05% 0.00% 0.06% 0.81% 0.14% 0.06% 5.79% 0.90% 1.70% 16.07% 9.61% 1.09% 0.58% 0.11% 0.38% 0.18% 1.61% 0.06% 0.03% 0.15% 0.11% 1.05% 0.60% 0.10% 0.03% 3.41% 3.28% 1.38% 1.20% 0.46% 2.60% 0.03% 0.09% 0.08% ROW 9.45% 8.15% 13.41% 7.22% 8.14% 9.93% 8.05% 13.31% 10.34% 12.78% 12.39% 11.38% 2.80% 12.76% 15.99% 19.92% 16.29% 9.69% 11.97% 10.28% 1.80% 7.39% 13.50% 20.21% 20.54% 12.18% 5.42% 14.40% 11.36% 7.57% 13.78% 5.70% 8.89% 13.48% 17.23% 11.01% 28.22% 26.90% 21.07% 15.90% 15.81% 27.96% 34.05% 29.67% 23.16% PAS 16.67% 19.28% 20.97% 11.92% 16.20% 16.35% 25.42% 24.75% 22.95% 16.18% 16.86% 12.91% 2.47% 5.61% 9.16% 13.92% 24.45% 5.74% 18.40% 8.10% 1.31% 4.05% 17.08% 23.80% 16.85% 18.64% 5.35% 17.09% 14.11% 3.46% 17.94% 21.00% 8.49% 15.43% 15.92% 11.10% 11.60% 17.82% 6.49% 7.15% 11.97% 12.98% 17.25% 20.91% 19.87% FOR 65.41% 63.01% 56.27% 70.58% 64.31% 56.47% 57.68% 50.80% 59.25% 62.79% 60.87% 68.86% 88.47% 75.41% 58.07% 58.16% 50.15% 44.08% 59.15% 58.52% 17.29% 42.59% 58.04% 49.79% 56.63% 58.22% 84.03% 59.57% 69.03% 85.00% 57.76% 67.89% 71.47% 60.20% 58.20% 71.67% 35.52% 35.04% 60.32% 66.98% 63.29% 33.84% 42.08% 42.10% 49.25% WET 4.14% 4.37% 2.17% 3.36% 3.90% 3.07% 1.96% 2.27% 1.44% 1.38% 1.30% 1.35% 2.40% 1.90% 2.45% 2.33% 1.74% 1.39% 1.71% 3.08% 1.77% 1.71% 2.19% 1.93% 1.61% 2.77% 1.51% 2.42% 2.48% 1.22% 2.91% 1.39% 2.25% 1.99% 1.41% 1.48% 3.76% 3.15% 2.40% 1.88% 2.21% 2.81% 2.01% 2.37% 1.95% BAR 0.03% 0.01% 0.05% 0.01% 0.04% 0.08% 0.02% 0.02% 0.01% 0.01% 0.04% 0.00% 0.00% 0.00% 0.00% 0.02% 0.06% 0.02% 0.00% 0.03% 0.00% 0.03% 0.03% 0.05% 0.00% 0.02% 0.00% 0.05% 0.01% 0.01% 0.01% 0.00% 0.04% 0.02% 0.81% 0.00% 0.00% 0.01% 0.06% 0.02% 0.06% 0.01% 0.01% 0.00% 0.03% WAT 1.03% 1.22% 0.86% 0.97% 2.82% 0.84% 0.69% 1.05% 0.73% 0.81% 0.76% 0.45% 0.12% 0.58% 1.65% 0.59% 1.38% 0.47% 1.65% 1.56% 0.56% 0.92% 1.32% 0.73% 0.75% 0.74% 1.34% 0.94% 1.02% 1.39% 0.78% 0.79% 0.80% 0.82% 0.75% 0.96% 2.97% 2.35% 0.36% 0.78% 1.75% 1.25% 0.80% 1.31% 1.20% % Disturbed 29.40% 31.39% 40.64% 25.09% 28.94% 39.54% 39.65% 45.87% 38.57% 35.00% 37.02% 29.33% 9.01% 22.11% 37.83% 38.91% 46.68% 54.05% 37.49% 36.81% 80.38% 54.74% 38.41% 47.50% 41.01% 38.24% 13.12% 37.01% 27.46% 12.39% 38.54% 29.94% 25.44% 36.98% 38.83% 25.90% 57.75% 59.46% 36.85% 30.34% 32.69% 62.09% 55.10% 54.22% 47.57% 1 4-3 Upper Rocky River Preliminary Findings Report February 2005 HUC1 UR10 UR11 UR12 UR13 UR14 1 Area (mi ) 1.59 1.88 1.59 1.72 1.38 2 RES 5.05% 4.23% 3.26% 7.95% 0.00% COM 0.42% 0.01% 0.03% 0.94% 0.18% ROW 18.95% 16.43% 19.13% 10.80% 17.70% PAS 15.70% 17.35% 20.11% 4.87% 14.50% FOR 54.27% 58.80% 54.52% 69.73% 62.26% WET 2.43% 2.64% 1.51% 4.35% 2.55% BAR 0.01% 0.00% 0.02% 0.01% 0.02% WAT 3.17% 0.54% 1.42% 1.35% 2.78% % Disturbed 40.12% 38.02% 42.52% 24.57% 32.39% 1 Percent Disturbed is the sum of Residential (RES), Commercial (COM), Row Crop (ROW) and Pasture (PAS) BC – Bear Creek Watershed MR – Middle Rocky River Watershed UR – Upper Rocky River Watershed Wetland 3% Water 1% Residential 5% Cropland 10% Wetland 3% Water 2% Residential 7% Commerical 1% Cropland 22% Pasture 16% Forest 50% Forest 65% Pasture 15% Bear Creek Wetland 2% Water Residential 1% 9% Upper Rocky Commerical 1% Cropland 13% Pasture 13% Forest 61% Middle Rocky Figure 4-1. Distribution of Land Uses Across the Rocky River 14-digit Hydrologic Units 4-4 Upper Rocky River Preliminary Findings Report February 2005 4.1.3 Impervious Area Coverage For modeling, an important characteristic of land use is the extent of impervious area coverage. Impervious areas represent the amount of the land surface that rainfall does not penetrate and includes roads, parking lots, and sidewalks. Imperviousness increases with the amount and density of development and affects the quantity and velocity of runoff and the quantity of contaminant washoff. Imperviousness estimates for the model are based on interpolation of percentages by lot size given in SCS (Soil Conservation Service, 1986) to the NLCD land use classes. Table 4-3 summarizes the assumptions used for each of the urban land uses included in the model. Rural land uses such as forest and pasture are assumed to be 100 percent pervious. Figure 4-2 shows the various impervious percentages per subwatershed. A detailed explanation of imperviousness calculations is provided in Appendix B. Of the 50 subwatersheds delineated for the study, only two had any significant levels of imperviousness. Central Siler City (MR07) had an estimated impervious coverage of 18 percent and Lower Loves Creek (MR08) had an imperviousness of 13 percent. The most recent update of the Center for Watershed Protection’s impervious cover model (ICM) indicates that streams are likely to be adversely impacted when impervious cover (IC) within their watershed reaches 10 percent or more, and that the level of degradation becomes significantly more likely and tends to be more severe at IC levels of 25 percent or more. In 2001, the Center completed a review of 225 research studies that measured a number of indicators of stream health relative to the amount of IC. The review reaffirmed that the IC range of 10-25 percent imperviousness was a strong predictor of stream degradation, and at levels of 25 percent or more, degradation was almost inevitable (Schueler, 2004). Even though thresholds of 10- and 25-percent have been identified, any imperviousness within a watershed has negative affects, sending increased flow volumes to local streams, causing erosion and stream instability. 4-5 Upper Rocky River Preliminary Findings Report February 2005 Liberty NC 49 ALAMANCE RANDOLPH Staley Rocky River Reservoir CHATHAM US 4 21 N 11t h US 64 Siler City US 1 42 NC 2 90 2 0 SCALE 2 4 Miles LEGEND 14-digit HUCs Subwatersheds County Boundaries Perennial Streams TIGER Major Roads Waterbodies Figure 4-2. Municipalities Level of Imperviousness 1 2 3-4 5-9 10 - 18 Impervious Percentages by Subwatershed 4-6 Upper Rocky River Preliminary Findings Report February 2005 Table 4-3. Land Uses and Estimated Impervious Percentages Land Use Name Abbreviation RVL RLL RML RMH RHH RVH COM PAS ROW FOR WET BAR WAT Percent Impervious 8 14 18 23 29 50 80 0 0 0 0 0 NA 1 Residential – Very Low Density (2+ acres per d.u.) Residential – Low Density (1.5-2 acres per d.u.) Residential – Medium Low Density (1-1.5 acres per d.u.) Residential – Medium High Density (0.5-1 acres per d.u.) Residential – High Density (0.25-0.5 acres per d.u.) Residential – Multifamily/Very High Density (< 0.25 acres per d.u.) Commercial/Office Pasture Row Crop Forest Wetlands Barren Water 1 Soil Conservation Service, 1986 4.1.4 Sewer Service Areas The watershed modeling techniques used distinguish between residential land uses served by sewer and those with onsite wastewater disposal systems (e.g., septic systems). For areas on sewer service, nutrient loading via wastewater is accounted for in wastewater discharge monitoring. Residences with onsite wastewater disposal also generate significant nutrient loads, but these must be accounted for in the watershed nonpoint source model (see Section 4.2). Thus, each of the residential land uses must be subdivided into sewered and unsewered fractions. No up-to-date, comprehensive coverage of sewer service areas was available for the entire watershed. In previous decades, type of wastewater disposal was identified for each household on the Census; however, for the 2000 Census, this question was included only on the detailed questionnaire sent to a statistical subset of households. To obtain a reasonable approximation of the extent of sewer service in the watershed as a whole, it was assumed that single-family households within municipal boundaries were on sewer service, while those outside municipal boundaries were not. Correspondence with the Siler City Planning Director confirmed that most of the city’s sewer service is within the municipal boundary. 4.1.5 Agriculture Runoff and pollution from urban areas is not the only area of concern in the study area. There is a much larger proportion of agricultural areas than urban areas, as can be seen from Figure 4-1. Management practices in these areas are of particular concern for their potential to deliver nutrients, metals, pesticides, sediment, bacteria and other pollutants to local stream systems. 4-7 Upper Rocky River Preliminary Findings Report February 2005 Agricultural areas including cropland, pasture, and hay land make up approximately 30 percent of the study area (USEPA, 1992). In 2000, the estimated poultry population for Chatham County was approximately 7 million birds and the cattle population was estimated at 16,000 to 17,000 head. Manure production from these animals produces a potential fertilizer supply that is far in excess of agronomic needs for all major nutrients with the exception of nitrogen, where manure supplies 82 percent of agronomic needs (NCSU, 2004). Thus, application of chicken litter and cow manure to pastures and cropland is ubiquitous, along with the associated potential for excess stress on the watershed from pollutant loading including organic matter, nutrients (phosphorus and nitrogen), and metals. Pollutant loading from cow manure is particularly problematic when cattle feeding areas are located adjacent to riparian areas. Direct deposition of feces into streams and accumulation of manure in adjacent riparian areas may be a primary mechanism of nutrient loading during baseflow periods. During storm events, overbank and overland flow may entrain manure accumulated in riparian areas resulting in pulsed loads of nutrients, total organic carbon (TOC), biological oxygen demand (BOD), and fecal coliform bacteria into streams. Stream reaches with particularly heavy loads of manure or with low stream velocities may accumulate heavy deposits of organic matter that may substantially degrade aquatic community support functions. Overgrazing by cattle in pastures near or adjacent to stream corridors increases sediment loads from hillslope (upland) areas. These pasture lands are often on highly erodible soils and on moderate to steep slopes (Figure 2-5). Overgrazing may leave many pastures with insufficient plant cover for much of the year, which can increase soil erosion risk. Local hydrology is also influenced by pasture management practices. Loss of plant cover reduces rates of infiltration and evapotranspiration. Cattle trampling may compact soils and further decrease infiltration rates. The combined effect of these processes is an increase in the volume and rate of storm runoff, resulting in increased overland flow, peak storm flows, and stream power, which in turn cause excess channel erosion that may destabilize stream sediment budgets. Cattle have free access to riparian zones in many areas and have reduced plant cover through overgrazing and trampling. The loss of plant cover on streambanks increases erosion rates during storm flows and increases the likelihood of mass wasting (slumping) of bank material. Streambank erosion is believed to be a primary management issue in the study area, affecting both habitat suitability and water quality. A GIS analysis was performed to determine which stream reaches had a high potential to deliver sediment (Section 4.4). Croplands have been identified in previous studies as having high potential for producing large sediment (Tetra Tech, 2004a) and nutrient loads to areas streams. In general, upland erosion rates in conventionally managed croplands are 5 to 10 times those of pasture. Despite the relatively small proportion of cropland in the study area, this land-use may have a disproportionate impact on water quality functions. 4.2 GWLF WATERSHED MODEL AND PRELIMINARY RESULTS Nonpoint loading of water and nutrients is simulated using the Generalized Watershed Loading Function (GWLF) model (Haith et al., 1992). The complexity of this loading function model falls between that of detailed simulation models, which attempt a mechanistic, time-dependent representation of pollutant load generation and transport, and simple export coefficient models, which do not represent temporal variability. GWLF provides a mechanistic, simplified simulation of precipitation-driven runoff and sediment delivery, yet is intended to be applicable as an assessment tool with or without formal calibration. Solids load, runoff, and groundwater seepage can then be used to estimate particulate and dissolved-phase nutrient delivery to a stream, based on concentrations in soil, runoff, and groundwater. The GWLF model has a long history of successful application in watershed studies throughout the eastern U.S. (e.g., Howarth et al., 1991; Dodd and Tippett, 1994; Cadmus, 1995; Swaney et al., 1996; Schneiderman et al., 2002; Lee et al., 2001; Evans et al., 2002). Model specifics are located in Appendix C. 4-8 Upper Rocky River Preliminary Findings Report February 2005 Based on the initial screening level modeling results, average areal loading rates for total nitrogen, total phosphorus, and upland sediment erosion across the study area subwatersheds are shown in Figure 4-3 through Figure 4-5. The highest nutrient loading rates are found in subwatersheds with high soil erosion rates and large areas of row crop and/or urban land uses. Subwatersheds with the highest nutrient loading rates are seen in the headwater areas of the Rocky River, Loves Creek, Johnson Creek, Mud Lick Creek, Varnell Creek, Tick Creek, and some areas of Bear Creek. In Bear Creek, manure wash-off from agricultural areas appears to be the primary source of nutrient loading. Many of these agricultural areas are located on shallow soils having little infiltration and high runoff rates. In headwater areas of the North Prong of the Rocky River and in three Loves Creek subwatersheds, urban land uses in and around Siler City and Liberty, NC are primary sources of total nitrogen and total phosphorus delivery to streams. 4-9 Upper Rocky River Preliminary Findings Report February 2005 NC -4 9 Johnson Creek ys C reek US -4 21 M ud Li ck Cr ee k Lac Lo ve sC re ek Major Roads TP Areal Loads (Lb/Acre/yr) 0.381 - 0.617 0.617 - 0.74 0.74 - 0.896 0.896 - 1.439 Figure 4-3. y ck Ro R er iv ree kC c Ni k US-64 y ck Ro k ee Cr k Ti c N k ee Cr 2 r 90 B ea C- Average Annual Total Phosphorus Loading Rates by Subwatershed n ell V ar ek Cre R er iv US 21 -4 N 0 2 4 Miles 4-10 Upper Rocky River Preliminary Findings Report February 2005 49 CN Johnson Creek Cr ee k Mu dL ic k L acy s Cr ee k Lo ve sC re e k Major Roads Subwatersheds TN Areal Loads (Lb/acre/yr) 1.675 - 2.687 2.687 - 2.962 2.962 - 3.362 3.362 - 8.427 c Ro ky ve Ri US -4 21 r ek Cre ck Ni US-64 c Ro k ee Cr k T ic N k 02 ree -9 rC C ea B k re e el l C Varn ky ve Ri r 21 ­4 US N 0 2 4 Miles Figure 4-4. Average Annual Total Nitrogen Loading Rates by Subwatershed 4-11 Upper Rocky River Preliminary Findings Report February 2005 NC -49 US -4 Roc ky R i ver 21 ys C reek Joh nson Creek M ud Lic kC re ek k ree kC Ni c Varn ell C k ree Lac US-64 re ek y ck Ro ve sC r ve Ri Lo Tic k ee Cr k k 02 -9 ree C rC N a Be N 2 -4 US 1 Major Roads Subwatersheds Erosion (Tn/Acre/yr) 0.149 - 0.549 0.549 - 1.128 1.128 - 1.831 1.831 - 3.534 2 0 2 4 Miles Figure 4-5. Average Annual Upland Erosion Loading Rates by Subwatershed 4-12 Upper Rocky River Preliminary Findings Report February 2005 4.3 EXISTING BUFFER DISTURBANCE ANALYSIS A GIS analysis was performed to estimate the percent of stream buffers that have been altered by human activities. A description of the analysis is in Section 4.4. The level of vegetation disturbance was assessed using National Land Cover Data (or MRLC) to tabulate areas of various land cover classes within each stream buffer and to calculate the percentage of area in human-altered land cover types (urban, transitional, commercial, residential, and agricultural). Results of the buffer analysis will be field verified during the Detailed Assessment phase. Preliminary results indicate high percentages of buffer disturbance in areas that are typically more likely to have significant buffer disturbances, such as urban areas and agricultural activities (Figure 4-6). Streams near Siler City and in high agricultural areas showed the highest levels of disturbance. Buffer disturbances are commonly associated with lawn maintenance, cattle access to streams, farming operations and construction activities. 4-13 Upper Rocky River Preliminary Findings Report February 2005 Liberty NC 49 ALAMANCE LEGEND RANDOLPH Staley Rocky River Reservoir CHATHAM US 42 1 11t h US 64 Siler City 14-digit HUCs Subwatersheds County Boundaries Perennial Streams TIGER Major Roads Waterbodies Municipalities Level of Buffer Disturbance 0 - 10% 10 - 30% 30 - 60% 60 - 100% US 1 42 N NC 2 90 2 0 SCALE 2 4 Miles Figure 4-6. Existing Buffer Disturbance in the Study Area 4-14 Upper Rocky River Preliminary Findings Report February 2005 4.4 REACH-LEVEL BANK EROSION RISK ANALYSIS A reach-based risk analysis was undertaken in the Rocky River study area to assess the risk factors for streambank erosion using widely available spatial databases including soils, land use, hydrography, and digital elevation models. The objective of this analysis is to assign risk categories to individual stream reaches that describe the relative risk of bank erosion based upon known factors that increase the likelihood of channel instability, including conversion of forest to agricultural and urban land uses at the watershed scale, disturbance of riparian buffers, and non-cohesive bank materials. The analysis of reach-level bank erosion risk began by developing polygons representing a 60m buffer around each perennial stream segment contained in a USGS 1:24K hydrography line coverage. The buffering procedure resulted in “square-ended” polygons and therefore they do not overlap. The risk of channel erosion along a given stream segment is assumed to be proportional to the inherent erodibility of riparian soils, the degree of disturbance of riparian vegetation, and relative runoff potential for contributing upland areas. The erodibility of soils within the riparian zone of a given stream segment was assessed using an areaweighted average soil erodibility factor (USLE K factor) within the 60-meter stream buffer polygon (Figure 2-5). These K factors were obtained from the NRCS STATSGO (1994) soil data coverage. An area- weighted average SCS curve number was developed for the contributing area of each segment to assess relative upland runoff potential. The significance of the curve number is explained in Section 6.1.1.1. This was accomplished by development of a grid of area-weighted curve numbers for the entire study using the ESRI Avenue request “flowaccumulation” and using a curve number grid as a weighting factor. The resulting grid returns the sum of all curve number values within the contributing area of any given reference cell. When this value is divided by the regular flow accumulation value, the average curve number is returned for each cell. This can be summarized as: Area Weighted Curve Number = Sum of CNs within contributing area Number of grids in contributing area These predictor variables (land disturbance, soil erodibility, and curve number) are then used to statistically classify each buffer polygon into bank erosion risk categories using a procedure called “Kmeans clustering.” The result of the cluster analysis was assigned to one of four risk categories: High, Moderate-High, Moderate-Low, and Low. There was high variability in the level of buffer disturbance of stream reaches initially assigned to the Moderate-High and Moderate-Low categories. The variability led to an underrepresentation of risk in some highly disturbed stream reaches based on field reconnaissance. Thus, stream reaches in the Moderate-Low category where buffer disturbance exceeded 12 percent were reassigned to the Moderate-High Category. Similarly, stream reaches in the Moderate-High category where buffer disturbance exceeded 50 percent where reassigned to the High Risk category. Thresholds for reassignment are based on results from the Upper Yadkin River Basin Detailed Assessment Report (Tetra Tech, 2003c). The Upper Yadkin River Basin shares similar physiographical properties as the Upper Rocky River watershed, such as soils and topography. The preliminary results of this analysis are presented in Figure 4-7. These results will be “groundtruthed” with a synoptic survey of several stream reaches in each vulnerability category based on qualitative assessment of bank erosion hazard. The results of this analysis will be used to target more detailed field-based assessments of stream channel geomorphology, restoration potential, and preservation potential. 4-15 Upper Rocky River Preliminary Findings Report February 2005 Liberty NC 49 ALAMANCE RANDOLPH Staley Rocky River Reservoir LEGEND CHATHAM US 42 1 11th US 64 Siler City 14-digit HUCs Subwatersheds County Boundaries Perennial Streams TIGER Major Roads Waterbodies Municipalities Stream Erosion Risk Low Medium - Low Medium - High High N US 1 42 NC 2 90 2 0 SCALE 2 4 Miles Figure 4-7. Stream Reach Bank Erosion Risk Categories 4-16 Upper Rocky River Preliminary Findings Report February 2005 4.5 ASSESSMENT OF TERRESTRIAL HABITAT FUNCTIONS AND PRESERVATION POTENTIAL Assessment of aquatic habitat functions was discussed in Section 3.3, whereas this section focuses on terrestrial habitat assessment. A summary of the key values used to assess terrestrial functions and preservation potential, along with a listing of the indicators used in their assessment and the tools used to perform those assessments, is presented in Table 4-4. Details of each assessment method and the corresponding results are discussed in the following sections. Table 4-4. Summary of Indicators and Tools Used for Preliminary Assessment of Terrestrial Habitat Functions and Preservation Potential Potential Value Forest Habitat Contiguousness High Quality Habitat Indicator Forest Cover Disturbance Forest Age/ Habitat Composition Scale Subwatershed* Subwatershed* Assessment Technique GIS Analysis 1) 2) 3) Wetland Distribution Species and Habitats of Special Concern National Wetland Inventory (NWI) Natural Heritage Element Occurrences Subwatershed* Subwatershed* GIS Analysis of GAP Natural Heritage Inventory Local Habitat Studies Watershed Function Terrestrial Habitat Functions GIS Analysis of NWI GIS Analysis *“Subwatershed” refers to smaller drainage areas within selected 14-digit hydrologic units delineated for the purposes of defining distinct management units within the context of Local Watershed Planning efforts, usually in the range of 1-5 square miles in area. 4.5.1 Purpose of Habitat and Preservation Potential Assessment Section 4.5 focuses on indicators of high value areas of the Bear Creek/Middle Rocky River/Upper Rocky River watersheds where functions are healthy and fully intact (or at least relatively unimpaired). Obviously, it is important to identify areas where habitat, water quality, hydrology and other such watershed functions have been degraded or lost, and determine the management and restoration measures necessary to recover those functions. It is also equally important to identify those portions of the watershed that have very high quality habitat, very pristine water quality, or flood storage capacity that is integral to the well-being of downstream segments. In addition to the authority to effect stream and wetland restoration for mitigation purposes, within its programmatic mission, NCEEP has the authority to direct funding to the preservation of riparian corridors (and possibly extending to some upland areas) that exhibit high quality habitat and/or high watershed functional value in terms of the contribution to hydrology or water quality. The purpose of the preliminary assessment set forth in this chapter is to best identify those riparian corridors that have the highest functional value in order to target such areas for preservation efforts. The following sections describe each of these indicators in detail. 4-17 Upper Rocky River Preliminary Findings Report February 2005 4.5.2 Terrestrial Habitat Assessment Metrics Five habitat metrics were used to measure the relative habitat value of each LWP subwatershed. The metrics are listed and the various data and information sources utilized to develop these metrics are described below. 1) Percent forest cover in each subwatershed. 2) Percent high priority habitats defined by the NC Gap Analysis Project (GAP) (NCGAP, 2003) vegetation species alliances (including all bottomland hardwood, floodplain forests, shrub habitats, and early successional habitats) within each subwatershed. 3) Percent National Wetlands Inventory (NWI) (USFWS, 1999) wetlands in the floodplain or riparian buffer of each subwatershed. 4) Presence of valuable habitat and rare species as defined by the Significant Natural Heritage Areas and Natural Heritage Element Occurrences (NHEOs), delineated by the NC Natural Heritage Program (NCDENR, 2003b). 5) Presence of groundwater recharge areas as defined by the Triangle GreenPrint Project (TLC, 2002). North Carolina GAP Project Habitat Data The vegetation land cover data from NCGAP was used to determine the percent of forest and high priority habitat, as defined below, in each subwatershed. NCGAP developed the vegetation data by extracting forested areas from the 1992-1993 National Land Cover Data. Aerial videos of the forested areas were then recorded across the state. The NCGAP staff visited selected sites that corresponded to the aerial footage and identified the common species at those sites. Using the species data as well as NWI and NRCS soils data, they developed decision rules to classify the satellite imagery (NCGAP, 2003). The NCGAP data for the Rocky River LWP study area is shown in Figure 4-8. The percentage forest cover for each subwatershed was determined by tabulating the area of deciduous, evergreen, mixed, and woody wetlands (excluding shrublands) in the NCGAP vegetation data and dividing by subwatershed area. The percent of forest by subwatershed ranged from about 40 to 95 percent, with a mean of about 65 percent. To determine the high priority habitats, representatives of the NC Wildlife Resources Commission advised NCEEP and Tetra Tech on the prioritization of the GAP vegetation data in a meeting on December 1, 2003. The vegetation species alliances given the highest priority by the advising resource professionals included all bottomland hardwood and swamp forests, floodplain forests, shrub habitats, and early successional habitats. The percentage of each subwatershed occupied by high priority habitat was determined by tabulating the area of the prioritized NCGAP vegetation types for each subwatershed and dividing by subwatershed area. The percent of high priority habitat by subwatershed ranged from about 6 to 36 percent, with a mean of about 20 percent. 4-18 Upper Rocky River Preliminary Findings Report February 2005 Figure 4-8. NCGAP Vegetation Alliance Data for Rocky River LWP Study Area 4-19 Upper Rocky River Preliminary Findings Report February 2005 4-20 Upper Rocky River Preliminary Findings Report February 2005 National Wetlands Inventory Data The extent of potential wetland preservation sites in the riparian buffer was determined using data from the National Wetlands Inventory (NWI; USFWS, 1999). NWI wetlands that contained emergent, forested, or scrub-shrub vegetation were considered. Geographic information system (GIS) polygons of the floodplain were created for each subwatershed, and, in accordance with NCEEP preservation guidelines, the polygons included a 300-foot buffer on each side of perennial streams since digitized FEMA maps were not available for the study area. The percent of vegetated NWI wetlands in the riparian buffer ranged from 0 to 100 percent, with a mean of 56 percent. Groundwater Protection Areas Triangle GreenPrint is a project undertaken by the NC Division of Parks and Recreation, the Triangle J Council of Governments, and the Triangle Land Conservancy (TLC) to facilitate development of a regional vision for open space in the Triangle. A GIS database was developed with the help of 140 open space professionals and local experts (TLC, 2002). One of the types of open space identified was water quality areas. These water quality areas include wetlands, stream buffers, and groundwater recharge areas. As a priority metric, the location of each subwatershed within a groundwater protection area was recorded. North Carolina Natural Heritage Program Data and Information Within the Rocky River study area, the North Carolina Natural Heritage program has designated six sites as significant natural heritage areas (SNHAs) and six natural heritage element occurrences (NHEOs). Additionally, three SNHAs lie outside the study area but are aquatic habitats and thus affected by preservation activities within the study area. The SNHAs are GIS polygons of ecologically significant natural communities, and the NHEOs are GIS points where rare species or natural communities have been observed. As indicated by Steve Hall and Linda Pearsall (2004) of North Carolina’s Natural Heritage Program, a habitat prioritization needs to include the SNHA and NHEO sites because many of these sites fall within common, non-priority species alliances in the GAP data. As a priority metric, the presence of SNHAs and NHEOs were recorded for each subwatershed (NCDENR, 2003b). The NHEOs for animals such as birds and fish were excluded because they can easily travel between subwatersheds. NHEOs classified as historic or destroyed were also excluded from the analysis. A description of all significant natural heritage areas within the study area as well as those immediately downstream of the study area that may benefit from protection in upstream subwatersheds is listed below (Hall and Boyer, 1992). The location of SNHAs and NHEOs are shown in Figure 4-9. Upper Rocky River Aquatic Habitat Upper Rocky River Aquatic Habitat is a Natural Heritage Area of state significance. This reach of the Rocky River stretches approximately 18 miles from the Rocky River Reservoir to just above the confluence of Bear Creek, and more than half of it lies within the Rocky River LWP study area. The Rocky River is one of Chatham County’s biological treasures as it is home to a diversity of mussels and is the principal world refuge for the federally endangered Cape Fear shiner and federal-candidate Septima’s Clubtail dragonfly. While the Upper Rocky River Aquatic Habitat includes only the Rocky River, three additional Natural Heritage areas discussed below include the river as well as the riparian community. (Multiple property owners) Rocky River Basalt Bluffs and Levees Rocky River Basalt Bluffs and Levees is a Natural Heritage Area of county significance. The Rocky River flows through this 435-acre site. Historical records for the presence of the Cape Fear shiner, Savannah shoremussel, and squawfoot mussel exist at this site; however, water quality degradation has led to the extirpation of these three species. The most prominent geologic feature of this site is a large flow of basalt that crosses the river just upstream of SR 2170 (Rives Chapel Ch. Rd). In contrast to 4-21 Upper Rocky River Preliminary Findings Report February 2005 downstream sites, this reach of the Rocky River has relatively few riffle areas. The vegetation is dry mesic oak-hickory forest grading into mesic mixed hardwoods. The variety of slope and aspect at this site provide habitat for a variety of subcommunities including mountain laurel, broach beech fern, and wild comfrey. The levee forest that grows along the old stagecoach road at the southernmost end of this site is one of the most outstanding examples in the county. Here the circumneutral to basic soils weathered from basalt are reflected by the presence of shagbark hickory, hackberry, southern sugar maple, buckeye, bladdernut, and coralberry. (Privately owned – Jurisdiction: Hickory Mountain and Matthews Township) Wood’s Mill Bend Wood’s Mill Bend is approximately two miles downstream of Rocky River Basalt Bluffs and Levees and is listed as a Natural Heritage Area of state significance. This 250-acre site includes pool and riffle habitat of the Upper Rocky River as well as a riparian area on either side of the river of mesic mixed hardwoods. This reach flows past steep rocky bluffs, is choked with large boulders, and lies just below an old breached mill dam. Judging by its habitat features, this site probably once held one of the richest aquatic communities in the Piedmont. The federally-endangered Cape Fear shiner, threatened Savannah shore mussel, and squawfoot mussel were historically recorded in the past at sites just upstream of Wood’s Mill Bend. According to NHEO data, the Cape Fear shiner was last observed in 1984 just downstream of this site. Six different species of mussels are still abundant at this site, including the rare notched rainbow. However, these species may also be decreasing in numbers due primarily to discharge from the Siler City Wastewater Treatment Plant. Although only about 30 acres of this natural heritage area is within the Rocky River study area, it is important to preserve the entire contiguous area due to the presence of aquatic species that require high water quality and riparian species, such as the otter and broad-winged hawk, that require large tracts of wild lands. (Privately owned – Jurisdiction: Hickory Mountain) 902 Laurel Bluffs and Mussel Beds 902 Laurel Bluffs and Mussel Beds is a Natural Heritage Area of state significance. This reach of the lower Rocky River features well-developed rocky riffles and pools. A diverse aquatic community is the most outstanding biological feature of this site. Historically this site was inhabited by the Cape Fear shiner and it possessed one of the most diverse mussel faunas in the Piedmont. During the most recent survey, the Septima’s Clubtail dragonfly was observed as well as six species of mussels, including the uncommon notched rainbow and the state threatened brook floater and squawfoot. The steep bluffs on the south side of the river are covered with mountain laurel interspersed with large beech, red oak and white oak. The moderately sloping land on the north side of the river is occupied by a medium-aged mesic mixed hardwood forest and a variety of wildflowers including bloodroot, hepatica and spring beauty. A diversity of avian species from the American redstart to the kingfisher, as well as a regionally rare otter, occupy these riparian areas. (Privately owned – Jurisdiction: Hickory Mountain) Bear Creek Aquatic Habitat The lower 393 acres of Bear Creek (from SR 1010 (Pittsboro Goldston Rd) to its confluence with the Rocky River) is listed as a Natural Heritage Area of state significance. Bear Creek flows into the Rocky River just outside the study area and strongly resembles the larger river. The Cape Fear shiner has been found in this section of the creek and a diverse mussel community is still present. The river bed consists of cobbles to medium-sized boulders, mixed with gravel, and the riffle pool habitat supports a diversity of aquatic animals. During the last sampling visit by the Natural Heritage Program, the Cape Fear shiner was not sampled due to its protected status, and due to the lateness of the sampling visit, no Septima’s Clubtail dragonflies were found. However, the finding of six species of mussels indicates that the water quality in this segment of Bear Creek is still fairly good. The main threat to the aquatic community along this reach is the proliferation of package treatment plants along the entire course of the watershed. 4-22 Upper Rocky River Preliminary Findings Report February 2005 Vegetation along Bear Creek also resembles the Rocky River. Willow-herb is abundant in the sunnier riffle areas, while arrowhead and pickerelweed occupy wet pockets. Black willow and sycamore form a scrub community on the larger rock and gravel bars in the creek bed. Mountain laurel is the dominant plant along steep bluffs and rock outcrops. Young to medium-aged hardwoods make up the forest along gentler slopes and narrow floodplains. Sycamore and river birch grow close to the creek, while farther from the river, bottomland species such as sweet gum and willow oak mix with mesic slope species including red oak and pignut hickory. The presence of a large number of hackberries and shagbark reflect rich soils that indicate that the woods along this reach might mature into a high-quality hardwood forest if left undisturbed. (Privately owned – Jurisdiction: Gulf and Oakland) Lower Rocky River/Lower Deep River Aquatic Habitat The Lower Rocky River/Lower Deep River Aquatic Habitat is a Natural Heritage Area of national significance and lies just outside of the Rocky River LWP study area, but is affected by activities within the study area. This 13-mile reach of aquatic habitat includes the Rocky River from just above the confluence of Bear Creek to its confluence with the Deep River, as well as 3 miles of the Deep River above and below the confluence of the Rocky River. This reach of the Rocky River contains the largest known population of Cape Fear shiner within its range as well as the largest remaining Septima’s Clubtail dragonfly population in the world. The Rocky River Dragonfly Riffles Natural Heritage Area overlaps a large portion of the Rocky River segment of this Natural Heritage Area and includes the riparian habitat. (Multiple property owners) Rocky River Dragonfly Riffles The Rocky River Dragonfly Riffles, located on the lower reach of the Rocky River, is listed as a Natural Heritage Area of state significance. This 283-acre site is located approximately 3000 feet outside of the Rocky River LWP study area just downstream of the confluence of Bear Creek with the Rocky River. As noted above, this reach contains the largest and most viable population of Cape Fear shiner and a large population of Septima’s Clubtail dragonfly. The extensive riffle habitat present at this site aerates the waters and provides ideal habitat for the shiner and clubtail as well as several species of mussels. The slopes of this stretch of river are populated by a mesic mixed hardwood forest dominated by beech, red oak, and white oak. Mountain laurel, white pine, and large fothergilla are also found here. The protection of the animal species at this site depends on the preservation of water quality in the entire Rocky River drainage basin. (Privately owned – Jurisdiction: Center, Oakland and Hickory Mountain townships) Donnelly Hardpan Bog Donnelly Hardpan Bog is a 64-acre Natural Heritage Area of state significance. This site contains one of the largest and least disturbed upland pools in the region. Hydrologically isolated pools such as this one represent a rare topographic feature within the state and they typically harbor distinctive communities of plants and animals. The pool is characterized by vegetation that is tolerant of long periods of inundation including several species of sedges, buttonbush, tag alder, and marsh fern. Large populations of spotted salamanders and the rare four-toed salamander both reside in the pool. A canopy of willow oaks and sweet gum characterize the upland swamp area surrounding the pool. (The Nature Conservancy – Jurisdiction: Matthews Township [Siler City Planning District]) Old Railroad Heath Glades Old Railroad Heath Glades is an 83-acre Natural Heritage Area of regional significance and is located within a large area of uplands characterized by poor drainage and acidic soils. Historic volcanic activity lends this site pale soil derived from ash flow, rhyolite, volcanic glass, and other pyroclastic rocks. The vegetation is adapted to the strongly acidic soil conditions and to shifts in moisture from hot and dry in summer to flooded in the winter. Hardwood forest is still present in the identified natural area despite that the majority of this region is covered by pine plantations. The sparse canopy is characterized by blackjack oaks and stunted post oaks. Beneath the canopy, large areas of heaths and bracken are interspersed with 4-23 Upper Rocky River Preliminary Findings Report February 2005 grasses and herbs, including dwarf iris, wild indigo, and wild quinine. The most striking feature of this site is the taxonomic diversity of the heaths. A total of eight species were observed including trailing blueberry, high bush blueberry, swamp doghobble, staggerbush, and huckleberry. The animal community at this site is of regional significance because many species are more typical of the sandhills and coastal plain. One large pool in the center of the site along with smaller temporary pools and wet depressions throughout the area creates a habitat similar to the Carolina bays. Dragonflies, the southern cricket frog, Georgia satyr, six-line racerunner, and cobweb skipper are some of the species present in the Old Railroad Heath Glades that are more typically found in the Carolina bay region and coastal plain uplands. Although much of the surrounding area has been converted to pine plantation, there is still an extensive area of hardwoods that appears to be in similar condition to the identified natural area that lies to the north, south and east of this site. The extensive nature of this tract adds to this site’s value to wildlife. (Privately owned – Jurisdiction: Bear Creek Township) 4-24 Upper Rocky River Preliminary Findings Report February 2005 Figure 4-9. Significant Natural Heritage Areas and Natural Heritage Element Occurrences 4-25 Upper Rocky River Preliminary Findings Report February 2005 4-26 Upper Rocky River Preliminary Findings Report February 2005 4.5.3 Terrestrial Habitat Scoring Methods The five metrics listed in Section 4.5.2 were used to calculate terrestrial habitat value/preservation potential scores according to the scoring system shown in Table 4-5 below. For the first three metrics, the percent vegetation cover calculations were divided into quartiles and ranked from lowest to highest percent area. Points were awarded based on the quartiles of each cover category (e.g., four points were awarded to habitat polygons in the top quartile for percent forest). In addition to the quartile scores, points were awarded for location within groundwater protection areas and the presence of SNHAs in each subwatershed, as shown in Table 4-5. Table 4-5. Scoring System for Terrestrial Habitat Preservation Potential Criteria First Quartile (Highest Scores) (% subwatershed forested, % high priority habitat, NWI wetlands) Second Quartile (% subwatershed forested, % high priority habitat, NWI wetlands) Third Quartile (% subwatershed forested, % high priority habitat, NWI wetlands) Fourth Quartile (Lowest Scores) (% subwatershed forested, % high priority habitat, NWI wetlands) Subwatershed is located completely within a groundwater protection area Subwatershed is partially located within a groundwater protection area Contains one or more Significant Natural Heritage Areas Score 4 3 2 1 2 1 2 4.5.4 Results of Terrestrial Habitat Assessment and Targeting of Preservation Efforts Habitat percentages and scores for each subwatershed are listed in Table 4-6 and Table 4-7, respectively, and habitat scores are displayed spatially in Figure 4-10. The subwatersheds in the headwaters of Bear Creek (Bear Creek Tributary 1 and Upper Bear Creek) received a score of 14, the highest total score for quality of terrestrial habitat and potential for preservation sites. Table 4-7 lists subwatersheds by priority score. The results of this analysis and plans for Detailed Assessment of these areas are further discussed in Section 6.3. 4-27 Upper Rocky River Preliminary Findings Report February 2005 Table 4-6. Terrestrial Habitat Metrics for the Rocky River LWP Subwatersheds Subwatershed Number BC02 BC03 BC04 BC05 BC06 MR07 BC14 UR12 UR13 UR02 BC13 UR09 BC11 MR08 MR15 MR22 MR12 BC07 BC09 BC12 UR07 MR01 MR05 MR09 MR13 MR16 MR20 MR21 MR11 UR11 MR02 UR06 UR05 UR03 UR01 UR10 MR03 BC08 MR04 UR04 Percent Forest 71% 60% 78% 70% 65% 49% 81% 57% 79% 41% 94% 53% 67% 57% 74% 76% 65% 63% 64% 74% 46% 68% 65% 64% 87% 87% 66% 63% 60% 63% 63% 42% 68% 67% 42% 59% 55% 57% 63% 72% Percent Priority Habitat 37% 29% 21% 27% 23% 7% 14% 26% 12% 24% 6% 25% 22% 8% 19% 15% 26% 35% 27% 17% 23% 17% 24% 23% 9% 8% 23% 21% 23% 24% 20% 20% 18% 12% 19% 21% 30% 31% 12% 12% Percent NWI Wetlands in Buffer 43% 0% 83% 86% 97% 0% 38% 50% 78% 65% 59% 54% 100% 58% 86% 72% 85% 0% 0% 69% 40% 9% 83% 100% 50% 63% 73% 0% 0% 86% 21% 82% 77% 27% 44% 55% 62% 89% 0% 0% Subwatershed Bear Creek Tributary 1 Bear Creek Tributary 2 Bear Creek Tributary 3 Bear Creek Tributary 4 Bear Creek Tributary 5 Central Siler City Harts Creek Johnson Creek Lacy Creek Liberty South Lower Bear Creek Lower Greenbriar Creek Lower Little Bear Creek Lower Loves Creek Lower Meadow Creek Lower Tick Creek Lower Varnell Creek Middle Bear Creek 1 Middle Bear Creek 2 Middle Bear Creek 3 Middle North Prong Middle Rocky River 1 Middle Rocky River 2 Middle Rocky River 3 Middle Rocky River 4 Middle Rocky River 5 Middle Tick Creek 1 Middle Tick Creek 2 Middle Varnell Creek Mud Lick Creek Nick Creek North Prong Headwaters Piney Grove Church Rocky River at Staley Rocky River Headwaters Rocky River Reservoir Rufus Brewer Sandy Branch Siler City North Staley South 4-28 Upper Rocky River Preliminary Findings Report February 2005 Subwatershed Tick Creek Tributary Upper Bear Creek Upper Greenbriar Creek Upper Little Bear Creek Upper Loves Creek Upper Meadow Creek Upper Rocky River Upper Tick Creek Upper Varnell Creek Welch Creek Subwatershed Number MR18 BC01 UR08 BC10 MR06 MR14 UR14 MR17 MR10 MR19 Percent Forest 72% 71% 45% 68% 70% 64% 65% 65% 52% 78% Percent Priority Habitat 25% 27% 27% 25% 14% 23% 19% 25% 28% 14% Percent NWI Wetlands in Buffer 97% 76% 93% 26% 92% 97% 0% 91% 87% 89% Table 4-7. Terrestrial Habitat Priority Scores for the Rocky River LWP Subwatersheds Percent Top Priority Habitat 1 1 2 2 1 2 3 2 1 1 1 3 4 3 2 4 3 4 2 2 1 2 4 1 2 Location of Subwatershed within a Groundwater Protection Area 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 0 Subwatershed Central Siler City Lower Loves Creek Middle Tick Creek 2 Nick Creek Rocky River at Staley Rocky River Headwaters Middle North Prong North Prong Headwaters Siler City North Staley South Harts Creek Liberty South Lower Greenbriar Creek Middle Varnell Creek Rocky River Reservoir Rufus Brewer Upper Little Bear Creek Bear Creek Tributary 2 Middle Rocky River 1 Piney Grove Church Upper Loves Creek Upper Rocky River Johnson Creek Lower Bear Creek Lower Meadow Creek Percent Forest 1 1 2 2 3 1 1 1 2 4 4 1 1 2 1 1 3 2 3 3 3 3 1 4 4 Percent NWI Wetlands in Buffer 1 2 1 1 1 2 2 3 1 1 2 3 2 1 2 2 1 1 1 3 4 1 2 2 3 Presence of SNHA in Subwatershed 0 0 0 0 0 0 0 0 2 0 0 0 0 0 2 0 0 0 2 0 0 2 2 2 0 Total Score 3 4 5 5 5 5 6 6 6 6 7 7 7 7 7 7 7 8 8 8 8 8 9 9 9 4-29 Upper Rocky River Preliminary Findings Report February 2005 Subwatershed Mud Lick Creek Upper Greenbriar Creek Upper Meadow Creek Upper Varnell Creek Welch Creek Lacy Creek Lower Tick Creek Middle Bear Creek 2 Middle Rocky River 4 Middle Rocky River 5 Middle Tick Creek 1 Upper Tick Creek Bear Creek Tributary 3 Lower Little Bear Creek Middle Bear Creek 1 Middle Bear Creek 3 Middle Rocky River 2 Middle Rocky River 3 Bear Creek Tributary 5 Lower Varnell Creek Sandy Branch Tick Creek Tributary Bear Creek Tributary 4 Bear Creek Tributary 1 Upper Bear Creek Percent Forest 2 1 2 1 4 4 4 2 4 4 3 2 4 3 2 4 3 2 3 2 1 4 3 4 3 Percent Top Priority Habitat 3 4 3 4 1 1 1 4 1 1 3 3 2 2 4 2 3 3 3 4 4 3 4 4 4 Percent NWI Wetlands in Buffer 4 4 4 4 4 3 3 1 2 2 3 4 3 4 1 3 3 4 4 3 4 4 4 2 3 Presence of SNHA in Subwatershed 0 0 0 0 0 2 2 2 2 2 0 0 0 2 2 2 2 2 0 2 2 0 0 2 2 Location of Subwatershed within a Groundwater Protection Area 0 0 0 0 0 0 0 1 1 1 1 1 2 0 2 0 0 0 2 1 1 1 2 2 2 Total Score 9 9 9 9 9 10 10 10 10 10 10 10 11 11 11 11 11 11 12 12 12 12 13 14 14 4-30 Upper Rocky River Preliminary Findings Report February 2005 UR06 UR08 UR01 UR02 UR07 UR10 UR03 UR04 UR05 UR14 UR13 MR01 MR04 MR07 MR08 MR05 MR11 MR12 MR13 MR16 MR03 MR10 UR11 MR02 UR09 UR12 MR09 MR06 MR19 MR14 MR15 MR18 MR17 MR20 MR21 MR22 BC10 BC14 BC12 BC05 BC01 BC04 BC08 BC06 BC07 BC11 BC13 BC09 BC02 N BC03 Major Roads Subwatershed Boundaries County Boundaries Habitat Priority Score 3-5 6-7 1 0 1 2 3 Miles USGS 1:24,000 K Hydrography Perennial Streams Intermittent Streams Waterbodies 8-9 10 - 11 12 - 14 Figure 4-10. Terrestrial Habitat Priority Scores for Rocky River LWP Subwatersheds 4-31 Upper Rocky River Preliminary Findings Report February 2005 (This page left intentionally blank.) 4-32 Upper Rocky River Preliminary Findings Report February 2005 5 Summary of Land Use Planning The Rocky River Local Watershed Protection (LWP) study area comprises six local government jurisdictions: Chatham County (63.20 percent); Siler City (25.62 percent); Randolph County (4.67 percent); Liberty (1.08 percent); Staley (0.40 percent); and Alamance County (5.03 percent). Tetra Tech reviewed existing land use, stormwater and zoning/subdivision regulations for these jurisdictions’ portions of the Rocky River Watershed, as well as planned land uses and policies as reflected in the Alamance County Destination 2020; Town of Siler City Land Development Plan (2003); Chatham County Land Use Development Plan (2001); and Randolph County Growth Management Plan 2002. This section provides an overview of the current regulations as well as the vision of future land development in the watershed, and the implications for high quality habitat, stream erosion, Total Phosphorus (TP) loading, and upland loading of Total Suspended Solids (TSS). 5.1 CURRENT REGULATIONS AND LAND DEVELOPMENT VISION FOR THE WATERSHED Chatham County Chatham County has two distinct planning areas in the Rocky River watershed: the water supply protection area north of the water supply intake extending to the county line (34.44 sq.mi.) and the unincorporated area to the north and south of the Siler City Extraterritorial Jurisdiction (ETJ) and extending to the LWP study area boundary (82.89 sq.mi.). Refer to Figure 5-1. The county’s current zoning in the water supply protection area is 1 unit/acre in the critical area with a 12 percent impervious surface limit. The balance of the water supply watershed is also zoned for one house per acre, with a 24 percent impervious surface limit for nonresidential development. Within a 2,500-foot corridor along the Rocky River, residential development is limited to one house per 5 acres. There is no zoning in the unincorporated area surrounding the Siler City ETJ. Development in this area is governed by the Planning Department’s rules on subdivision and Health Department regulations on septic tanks. The latter requires a minimum 1-acre lot to accommodate a septic field. Chatham County’s vision for these planning areas is to maintain rural and agricultural land uses according to the plan. The Chatham County Land Use Development Plan defines rural as 1 to 5 acres per house. The development could be in a traditional subdivision (e.g., 1-acre lots), large lots, or a clustered design with houses built on smaller lots and 50 percent of the development tract preserved in open space. The existing 5-acre zoning in the Rocky River Corridor would remain intact. The Land Use Development Plan (2001) recommended that incentives be given to maintain existing farmland, and that a committee be formed to work out the details of how a rural agricultural district could be implemented. Chatham County’s website is http://www.co.chatham.nc.us. Siler City Siler City has a three-mile ETJ around its existing corporate limits. This area is currently un-zoned (except for the River Corridor); however, the Town of Siler City Land Development Plan provides a vision for the area. General residential development (2 to 4 units per acre) is planned for the areas south, west, and north of the city limits. Major industrial and mixed-use development is planned along the old Highway 421 and new Highway 421 corridors, north and east of the existing city limits. Rural and agricultural land uses are planned for the northern portion and the southern half of the ETJ. This area is projected to be low-density development with no public water and sewer service provided in the future. 5-1 Upper Rocky River Preliminary Findings Report February 2005 Siler City has very protective river and stream buffer requirements: within a 2,500 foot corridor along the Rocky River, 200-foot buffers are required along perennial and intermittent streams. Outside this corridor, 100-foot and 50-foot buffers are required along perennial and intermittent streams, respectively. (Refer to Figure 5-2.) Randolph County, Liberty and Staley Randolph County and its incorporated Towns of Liberty and Staley are in the northwestern headwaters of the LWP study area. The area is characterized by farmland and low-intensity urban development. The state’s WS-III watershed regulations apply to this area, and include the following requirements: • Low Density Development o Single-family residential development is limited to two houses per acre or 24 percent built upon area for all other residential and nonresidential development. • High Density Development o Residential and nonresidential development cannot exceed 50 percent built-upon area. Development must control the runoff from the first 1-inch of rainfall. o Ten percent of the jurisdiction may develop up to 70 percent built-upon area without stormwater controls. o A 100-foot buffer is required for all development exceeding the low-density requirements. The Randolph County Growth Management Plan 2002 shows the Town of Liberty more than doubling its municipal area in the coming years, and the land between Liberty and Staley targeted for a primary growth area. The vision for almost the entire area is high-density, mixed use urban development. Alamance County Alamance County’s jurisdiction in the Rocky River watershed is predominantly farmland (crops and hay/pastures). This area is also governed by the state’s WS-III Water Supply Protection regulations as described above. The Alamance County Destination 2020 does not envision any additional stormwater or water quality protection requirements for this area. 5.2 IMPLICATIONS FOR TERRESTRIAL HABITAT AND WATER QUALITY 5.2.1 Terrestrial Habitat Unless the existing regulations are significantly strengthened, a number of high quality (total score of 9 to 11, see Section 4.5.4) and very high quality (total score greater than 11) habitat areas are threatened in Rocky River’s planned rural areas (see Figure 5-3). Chatham County’s and Siler City’s vision of a large agricultural and rural district could be protective of habitat functions if the density allowed is on the midto-low end of the category’s defined density (1- to 5-acre lots). Based on Tetra Tech’s work in other areas of the region, the rural and agricultural district would need to have a minimum of 3- to 5-acre lots or cluster development with stormwater controls in order to protect habitat functions—again, significantly lower than the density currently allowed. 5-2 Upper Rocky River Preliminary Findings Report February 2005 US -4 R 2 1 oc k y Ri ver Staley US-64 Siler City ck Ro Cr ee k y r ve Ri Lo ve s Cr Ti ck US 21 -4 2 90 CN eek reek ar C Be N 2 0 2 Miles Rocky River Subwatersheds Siler City Extra-Territorial Jurisdiction Water Supply Protection Area Rocky River Corridor Rocky River Subwatersheds Waterbodies Major Roads County Boundaries Municipalities Chatham County Figure 5-1. Chatham County Planning Jurisdiction within the Rocky River Study Area 5-3 Upper Rocky River Preliminary Findings Report February 2005 UR14 MR02 MR03 UR13 UR14 MR01 MR05 MR12 MR04 MR11 MR10 US-64 Siler City MR08 MR07 MR09 MR13 MR16 MR06 MR14 2 -4 US MR19 MR17 N 1 MR21 MR15 MR18 MR20 0.8 0 0.8 1.6 Miles Perennial Stream Buffers Intermittent Stream Buffers Rocky River Corridor Stream Buffers Rocky River Corridor Rocky River Subwatersheds USGS 1:24,000 K Hydrography Perennial Streams Intermittent Streams Major Roads Siler City ETJ Municipal Boundary Figure 5-2. Siler City Planning Jurisdiction and Buffer Requirements 5-4 Upper Rocky River Preliminary Findings Report February 2005 Liberty UR08 UR11 Staley UR13 Siler City MR12 MR13 MR14 MR16 BC05 BC08 BC06 BC01 BC04 N BC02 3 0 3 6 Miles Rocky River LWP Study Area Municipalities County Boundaries Extra-territorial jurisdiction for Siler City High Quality Habitat Watersheds Very High Quality Habitat Watersheds Rocky River Subwatersheds Figure 5-3. High Quality Habitat Areas Threatened in Future Rural/Agricultural Areas 5-5 Upper Rocky River Preliminary Findings Report February 2005 Some high quality habitat areas in Siler City’s ETJ are projected to have urban development. Three high quality habitat areas are threatened in the eastern ETJ with planned major industrial and mixed urban uses. One very high quality habitat area in the southern ETJ is threatened by urban residential land use (see Figure 5-4 below). Liberty Staley MR05 Siler City MR09 MR19 MR18 N 3 0 3 6 Miles Rocky River LWP Study Area Municipalities County Boundaries Extra-territorial jurisdiction for Siler City High Quality Habitat Watersheds Very High Quality Watersheds Rocky River Subwatersheds Figure 5-4. High Quality Habitat Areas Threatened in Future Urban Areas 5-6 Upper Rocky River Preliminary Findings Report February 2005 5.2.2 Stream Erosion Based on the modeling results from the reach level bank erosion risk analysis (see Section 4.4 and Figure 4-7 for risk definitions and summary of results), the following observations were made related to land use. Chatham County Most of the streams and watersheds in Chatham County’s water supply watershed zone have medium to high erosion risk factors. If current zoning continues, or if the housing density in the agricultural and rural district averages 2 acres or less per lot, significant stream erosion is likely to occur in these subwatersheds. The Lick Creek watershed south of Siler City has medium to high erosion risk factors. Currently, this area has no zoning. Again, the envisioned agricultural district in these subwatersheds would need to average 3to 5-acre lots or clustered residential design to mitigate potential erosion impacts. Siler City For the most part, the streams with medium to high risk of erosion are in the developed portion of Siler City. Most of the streams in the ETJ have low risk factors; therefore future development does not pose significant risk of erosion. The exception is in the Loves Creek subwatershed in the southern portion of the ETJ. Alamance County The North Prong Rocky River and Greenbriar Creek have medium risk factors for erosion. Half-acre lots, which are allowed under the state’s WS-III water supply protection regulations, would pose a significant threat of erosion in these subwatersheds. Randolph County, Liberty, and Staley The Rocky River and North Prong Rocky River are in the planned primary growth area, which will include high-density, mixed-use urban development. Such development could cause significant erosion in the headwaters of the Rocky River watershed. 5.2.3 Upland Sediment Loading Tetra Tech conducted modeling to estimate current runoff of sediment from areas upland of streams and lakes (Figure 4-5). The modeling considered the subwatersheds’ soil type, slope, and land cover. The model predicted areas with higher erodibility factors, steeper slopes, and with more farm and barren land resulting in higher sediment loading (see Figure 5-5). It is important to note that the model did not consider the influence of any existing BMPs that may be in place. Therefore, the estimated loading may be higher than actual loading. Ten of the eleven subwatersheds that were estimated to have excessive loading rates (4.1 lb/ac/yr or greater) compared to other subwatersheds in the study area are in the Rocky River water supply protection zones of Chatham, Alamance and Randolph counties. All of the subwatersheds are in areas that are predominantly farm and barren land. This has several implications for predicting future sediment loading: • Farms that are preserved and maintained in the future should be encouraged to use best management practices to the maximum extent possible; • As agricultural land is converted to forest land or developed land in the future, there will be a reduction in sediment delivery to the stream system due to the decrease in disturbed soils from agricultural practices (tilling, grazing, etc.); 5-7 Upper Rocky River Preliminary Findings Report February 2005 • Those subwatersheds with excessive sediment loading also have streams with medium to high erosion risk factors (see Figure 5-6). Land disturbed for development, road building, utilities, etc., will need added attention to sedimentation and erosion controls and enforcement. Liberty N ALAMANCE C -4 9 RANDOLPH CHATHAM Staley U S42 1 Siler City US-64 21 -4 US N 2 90 CN 2 0 2 Miles Soil Erodibility Factor (Weighted) .13 .21 .26 .28 .34 Waterbodies 0.149 - 0.549 0.549 - 1.128 1.128 - 1.831 1.831 - 3.534 Upland Sediment Erosion (Tn/ac) County Boundaries Municipalities Major Roads 14 Digit Hydrologic Units Figure 5-5. Relationship Between Upload Sediment Erosion and Soil Erodibility Factor 5-8 Upper Rocky River Preliminary Findings Report February 2005 Liberty ALAMANCE CHATHAM RANDOLPH Staley Siler City N 1 0 1 2 Miles Upland Sediment Erosion (Tn/ac) 0.149 - 0.549 0.549 - 1.128 1.128 - 1.831 1.831 - 3.534 Water Supply Protection Zone Erosion Risk Factors High Medium High Figure 5-6. Bank Erosion and Sediment Threats to Subwatersheds 5-9 Upper Rocky River Preliminary Findings Report February 2005 5.2.4 Phosphorus Loading Tetra Tech estimated existing phosphorus loading in the Rocky River subwatersheds based on the potential for septic tank loading, farmland runoff (particularly from manure applications), urban runoff (e.g., lawn fertilizer), and soil erosion (Figure 4-3). Figure 5-7 shows subwatersheds with high (0.8 to 1 lb/ac/yr) and excessive (greater than 1.0 lb/ac/yr) phosphorus loading relative to the other subwatersheds in the study area. All of the subwatersheds, except three, are in existing urban areas (Siler City and Liberty) and in the rural Rocky River water supply protection zones of Chatham, Alamance, and Randolph counties. How future development affects these phosphorus-loading rates will vary by subwatershed, depending on the soil type, type of sewer service provided, and intensity of development. In some subwatersheds, conversion of agricultural land to developed land will result in a net decrease in phosphorus loading, in others a net increase. Many subwatersheds in the southern half of the Rocky River watershed are still primarily forested. These subwatersheds could significantly increase their phosphorus loading to streams as land is converted to residential development. To address excessive loading of phosphorus from future development, Tetra Tech will develop recommended BMPs in the upcoming Detailed Assessment and Targeting of Management Report for the Rocky River Watershed and recommend farmland BMPs and urban retrofits to address existing excessive loading. 5-10 Upper Rocky River Preliminary Findings Report February 2005 Liberty Staley Siler City N 3 0 3 6 Miles Rocky River LWP Study Area County Boundaries Extra-territorial jurisdiction for Siler City Municipalities Excess Phophorus Loading High Phosphorus Loading Rocky River Subwatersheds Water Supply Watersheds Figure 5-7. Subwatersheds with Elevated Levels of Phosphorus Loading 5-11 Upper Rocky River Preliminary Findings Report February 2005 (This page left intentionally blank.) 5-12 Upper Rocky River Preliminary Findings Report February 2005 6 Prioritizing Functional Stressors and Areas for Detailed Assessment One of the purposes of the Local Watershed Planning process is to determine the watershed functions within the study area that are being affected by current land management practices. The watershed functions identified by the EEP include water quality, habitat and hydrology. Habitat consists of both aquatic and terrestrial and is defined as all of the physical, biological and chemical characteristics necessary to maintain an organism’s viability. Specific descriptions and detailed explanations of the watershed functions listed above can be found in the Report from the Watershed Needs Assessment Team to the Mitigation Coordination Group (NCEEP, 2003) and can be downloaded from http://www.nceep.net/news/reports/WNAT%20Mit%20Group%20Final.pdf. A stressor is any physical, chemical, or biological entity that can induce an adverse response to watershed functionality. During the course of the preliminary investigations, key stressors were identified and quantified, using the best available data, which had significant effects on watershed functions. An indicator is a measurable characteristic, such as nutrient loading, that can be used to evaluate the level at which a particular function occurs. Table 6-1 provides a summary of the stressors identified during the watershed characterization, their relationship to watershed functions and the key indicators proposed to be used to quantify watershed benefits from initiating restoration and management practices in the study area. Table 6-1. Relationship Between Watershed Functions and Stressors for the Upper Rocky River Study Area Stressor Upland Runoff Riparian Buffer Disturbance Nutrient Loading Overland Sediment Loading Watershed Function(s) Affected Hydrology Hydrology, Water Quality, Habitat Water Quality, Habitat Water Quality, Habitat Indicator Channel Stability Riparian Buffer Disturbance Existing Nutrient Loads Existing Overland Sediment Loads The remaining portions of Section 6 will provide more detail into the selection of the stressors and the objectives for detailed assessment. Section 7 focuses on the specific indicators and assessment tools that will be used for the Detailed Assessment and Management Report. 6.1 PRIMARY THREATS TO WATERSHED FUNCTIONS AND OBJECTIVES FOR DETAILED ASSESSMENT The next phases of the project, Detailed Assessment and Management Report, will expand on the Preliminary Findings results validating the hypotheses from the scoping level of analyses using field studies, and recommending specific management projects (restoration, preservation, or a combination thereof) for the implementation team to make informed decisions on the best projects to pursue. The Detailed Assessment and Management Report will address specific management measures, quantifying expected watershed benefits where possible. Thus, it is important to summarize the Preliminary Findings to ensure that detailed assessment and management planning are focused on the most important threats to watershed function. 6-1 Upper Rocky River Preliminary Findings Report February 2005 The evaluation of existing data and assessment information summarized in Sections 1 through 5 reveals a consistent pattern of functional degradation associated with urbanization and intensive agriculture. A number of factors contribute to this functional degradation. Agricultural management practices appear to be the most widespread cause of watershed function degradation, although the magnitude of urban stressors and potential of future urbanization around Siler City is expected to make urban sources of water quality stressors increasingly important over time. The greatest threats to existing watershed functions appear to be occurring in the Upper Rocky River area, associated with intensive agricultural activities including cropland and pasture with extensive land application of manure and pervasive lack of sufficient riparian buffers. The majority of subwatersheds with the highest total phosphorus and total nitrogen loads occur in this portion of the study area (Figure 4-3 and Figure 4-4). NCDWQ monitoring of the Rocky River Reservoir indicated hypereutrophic conditions during several visits in the summer of 2003. One of two 303(d) listed stream segments in the study area is located on the Upper Rocky River with agriculture (cropland) and pasture listed as potential sources of impairment. In terms of terrestrial habitat, few of the quality wildlife habitat areas (described in Section 4.5) are located in the Upper Rocky River watershed. Given the results of this preliminary watershed characterization, the detailed assessment will focus on the primary stressors of upland runoff and riparian disturbance, nutrient loading, and overland sediment delivery. (Note: Fecal coliform bacteria is also considered a stressor due to excessive chicken manure application and cattle access to streams. This parameter will be addressed qualitatively in terms of being associated with the sediment and nutrient reduction practices. Additional monitoring locations for fecal coliform are recommended in Section 8.) Each of these stressors is discussed in more detail in Sections 6.1.1 through 6.1.3, with a brief description of the Detailed Assessment objectives included. 6.1.1 Upland Runoff and Riparian Condition Hydrologic functions are fundamental driving forces of water quality and habitat support functions in both streams and wetlands. Changes in stream power caused by reduced upland plant cover and cattle induced soil compaction can contribute to streambank instability, changes in stream morphology, increased bank erosion, down-cutting, and head-cutting. However, because the riparian zone marks the transition between terrestrial and aquatic (stream) systems, there are several hydrologic stressors that are unique to riparian areas and require special assessment techniques and management practices. The remainder of Section 6.1.1 will describe the proposed indicators of hydrologic functions and techniques or methodologies to assess them. 6.1.1.1 Upland Runoff Upland runoff is influenced by a variety of land management practices including cropland and pasture management in rural areas and creation of impervious surfaces in urban settings. The combined effect of these processes is an increase in the volume and rate of storm runoff, resulting in increased overland flow, peak storm flows, and stream power. This may destabilize stream channels and yield bank and channel erosion that may destabilize stream sediment budgets. A simple indicator of field scale hydrologic conditions in upland areas is the SCS curve number. The number is a numeric index that summarizes runoff potential from a given HRU, or hydrologic response unit (i.e., unique land use/soil type combination), based upon vegetation type and condition, soil physical properties, and impervious surface. The numeric target is to return SCS curve numbers closer to those observed in reference reaches. An analysis of changes in curve numbers can be accomplished using land use/land cover, and soil series data. The process is partially automated using available watershed modeling packages including GWLF. A database of soil and land use patterns has already been developed in the subwatershed delineation 6-2 Upper Rocky River Preliminary Findings Report February 2005 process. This database can be used to calculate current and future curve numbers for scenarios that will reflect changes in pasture condition resulting from implementation of BMP scenarios. Objective for Detailed Assessment: • Identify the subwatersheds with the greatest potential for excessive runoff and identify candidate areas for restoration, BMPs, and management efforts to address this issue. Stressors: Excessive upland runoff to area streams 6.1.1.2 Riparian Conditions Riparian zones are functionally important as buffers between upland areas, which are often sources of stressors such as nutrients, sediments, and runoff, and aquatic ecosystems, which are sources of many of the watershed functions that are of priority to NCEEP. When properly functioning, riparian zones trap or transform sediment and nutrients, and slow or desynchronize delivery of upland runoff to streams. Riparian vegetation plays an important role in enhancing the cohesiveness of streambank materials and limiting the rate of bank erosion, which is a primary source of stream habitat degradation. Channel stability is said to occur when the processes of sediment erosion and deposition are in a state of dynamic equilibrium over time. When more sediment enters a stream than the stream can clear, the stream aggrades, filling in pools, altering substrate, and destroying habitat. When the stream’s sediment transport capacity exceeds the sediment supply, the stream will create additional sediment supply by eroding the channel. Channel erosion occurs through three primary processes: widening, down-cutting, and mass wasting of bank material. Mass wasting creates large pulses of sediment into streams. The contribution of channel erosion to sediment loading in streams is largely a function of stream class, stage of channel evolution, and channel stability. During a visual reconnaissance of stream conditions in the study area, substantial channel instability has been noted at multiple locations (see Section 3.3). Typically, the most likely local causes of instability appeared to be local riparian management such as cattle access to streams and agricultural management practices in rural areas, and replacement of woody riparian vegetation with grass in urban settings. However, more detailed analysis of geomorphic indicators at representative cross sections is required to draw definitive conclusions regarding reach scale and watershed scale factors contributing to channel instability. Objectives for Detailed Assessment: • Further quantify the impacts of upland runoff on area streams and identify potential agricultural BMPs, urban BMPs, and stormwater BMP retrofit opportunities to alleviate those impacts. • Determine the need for stream restoration along study area streams, and identify reaches where restoration would be feasible and beneficial. Stressors: Riparian buffer disturbance Erosive stream velocities and increased sediment from stream erosion 6.1.2 Nutrient Loading to Area Streams and the Rocky River Reservoir Nutrient concentrations have not been identified as a significant threat to the health of flowing streams within the study area. Nutrients contribute to water quality degradation and nutrient loads generated from the study area are of concern for the lakes receiving this flow, especially the Rocky River Reservoir, which had a recent hypereutrophic rating from DWQ. Excess nutrient loads can lead to algal blooms that are unsightly, degrade recreational opportunities, alter biological uses and water quality, and present problems for treatment for use as potable water supplies. 6-3 Upper Rocky River Preliminary Findings Report February 2005 Objectives for Detailed Assessment: • Identify the subwatersheds with the greatest potential to deliver nutrients to the Rocky River Reservoir from tributary streams and target them for management efforts to reduce those loads. • Recommend management practices on a site-specific basis to alleviate nutrient stress on the reservoir and quantify the effects of such management practices. Stressors: Nutrient loading and eutrophication 6.1.3 Upland Sediment Delivery Upland sediment delivery to local stream systems causes high concentrations of fine sediments that adversely impact stream ecosystems by decreasing light penetration through the water column, filling pore spaces in the streambed and choking the stream with more sediment than the stream can balance. Suburban development leads to increased soil erosion and higher sediment loadings in nearby streams. Agricultural activities involving earthwork and overgrazing activities tend to leave large areas of land exposed, increasing the potential for sediment loss. Cattle access to streams allows streambanks to be trampled and riparian buffers to be destroyed, causing bank erosion and slumping. Objective for Detailed Assessment: • Identify the subwatersheds with the greatest potential to deliver sediment to local streams and target them for restoration and management efforts to reduce those loads. Stressors: Sediment loading 6.2 PRIORITIZING SUBWATERSHEDS FOR DETAILED ASSESSMENT OF RESTORATION NEEDS One of the primary purposes of the preliminary assessment is to target selected LWP subwatersheds for Detailed Assessment. Based on the results of this preliminary functional assessment, a ranking system was developed to assess each of the LWP subwatersheds for potential degradation. Using the results from the pollutant modeling (Section 4.2), the imperviousness percentage analysis (Section 4.1.3), and the reach level erosion risk analysis (Section 4.4), a scoring system was developed according to the point system shown in Table 6-2. The purpose of the ranking system is to identify those subwatersheds with the highest risk points based on the scoping level modeling and GIS analysis to be targeted for further investigations. The intent is also to target those subwatersheds with the highest risk points for management efforts to restore watershed functionality. Since no significant development is expected to occur within the study area, future land use conditions were not taken into account in the scoring system. Future development is expected to occur in those subwatersheds that already have a significant amount of imperviousness. The Detailed Assessment will recommend BMPs and restoration opportunities to improve conditions and prevent further degradation. To differentiate subwatersheds, risk points were established for four risk categories under the scoring system: low, medium (med), high, and very high. Definitions for each risk category were established for the five primary indicators used in the preliminary functional assessment: riparian buffer condition, imperviousness, phosphorus loading rate, nitrogen loading rate, and upland sediment loading rate (Table 6-2). For the latter three indicators, the four levels of risk were assigned to the four quartiles of average annual subwatershed loading rates for existing land use conditions. The results of the quartile analysis are provided in Appendix F. 6-4 Upper Rocky River Preliminary Findings Report February 2005 Table 6-2. Scoring System Used to Rank Subwatersheds for Restoration Priority Indicator Risk Points Low Risk 0 Med Risk 1 High Risk 2 Very High 3 Risk Definitions Riparian Buffer Condition Low Risk = 10% buffer disturbance or more Med Risk = 20% buffer disturbance or more High Risk = 30% buffer disturbance or more Very High = 40% buffer disturbance or more Imperviousness Med Risk = 10% imperviousness or more High Risk = 25% imperviousness or more Nitrogen Loading Rate Subwatershed sorted and rated by quartile lbs/acre/yr Phosphorus Loading Rate Subwatershed sorted and rated by quartile lbs/acre/yr Upland Sediment Loading Rate Subwatershed sorted and rated by quartile tons/acre/yr 2 4 0 1 2 3 0 1 2 3 0 1 2 3 It should also be noted that in the course of organizing and evaluating the array of indicators used in this analysis, it became very apparent that a clear distinction existed between LWP subwatersheds that are predominantly rural in nature and those that are predominantly urban. The distinction is apparent in the stressors and the degree to which functions are affected within the two groups of subwatersheds. In the rural subwatersheds, existing degradation is often a function of current or past agricultural practices, whereas in urban subwatersheds the impacts of existing development are associated with loss of forest cover, increased imperviousness, and increases in stormwater runoff and nonpoint source pollutant loads. Subwatersheds in urban areas that are determined to have high functional deficits will be investigated for BMP opportunities. In rural areas, agricultural BMPs and exclusionary fencing will be recommended. The split between urban and rural subwatersheds is illustrated in Figure 6-1. Urban subwatersheds were determined by including existing municipal boundaries and proposed future development. 6-5 Upper Rocky River Preliminary Findings Report February 2005 h Pr N ort Liberty UR06 Gree r nbria R on g UR08 UR07 UR01 UR02 UR03 UR09 UR12 UR11 Staley Ro ck yR iv e r UR04 UR05 ocky R ive Cree k UR14 MR07 MR06 UR10 r MR02 UR13 MR01 MR03 MR10 MR11 MR12 MR05 MR04 MR08 SILER CITY # WWTP MR09 MR13 y ck Ro Siler City MR19 MR14 MR16 MR18 MR15 MR21 T ick MR20 ek Cr e R er iv MR22 BC10 BC08 BC14 BC11 BC12 MR17 N BC01 BC05 BC04 BC06 BC09 BC07 k Cree Bear BC13 BC02 BC03 2 0 2 4 6 Miles NWI wetlands Municipal Boundaries Urban subwatersheds Rural Subwatersheds Study Area Subwatershed Boundaries Roads # Major NPDES Dischargers USGS 1:24,000 K Hydrography Perennial Streams Intermittent Streams Figure 6-1. Urban vs. Rural LWP Subwatersheds 6-6 Upper Rocky River Preliminary Findings Report February 2005 The combined scores for indicators showing the priority for restoration and other management efforts are presented for subwatersheds in Table 6-3 and are illustrated spatially in Figure 6-2. When examining Figure 6-2, it is important to note that the subwatersheds are grouped by color according to their final scores. Higher scoring subwatersheds are reflected in lighter colors, denoting higher functional deficits. Although there are also functional deficits in some of the other watersheds, the primary degradation was determined to lie within these selected subwatersheds. Urban subwatersheds are distinguished in Table 6-3 by a shaded row. Based on the results of the scoring analysis, the subwatersheds with the highest stress levels are Central Siler City (MR07), Lower Loves Creek (MR08), Middle Tick Creek 1 (MR20), Rocky River Headwaters (UR01), Liberty South (UR02), Middle North Prong (UR07) and Johnson Creek (UR12). MR07 and MR08 are the most urbanized of the seven subwatersheds, with high potential for excessive nutrient loadings and stream degradation. Loves Creek is on the 303(d) list, so focusing restoration and management recommendations in this subwatershed could improve existing water quality. UR01, UR02 and UR07 contribute flow to the Rocky River Reservoir. Initial modeling results indicate high potential for overland sediment delivery and excessive nutrient loadings to local streams, the latter which may be contributing significantly to the hypereutrophic condition noted by DWQ in their water quality summary. UR01 and UR02 are at the southern boundary of the Town of Liberty so urban stressors play a role in the existing degradation. UR07 is primarily agricultural and investigations will be performed to determine potential water quality stressors. The criterion for selecting the targeted subwatersheds was based on the score for MR06, Upper Loves Creek. Due to Loves Creek’s impaired status, it was reasonable to assume that any scores that occurred within Loves Creek’s watersheds should reflect a degraded status. MR06 had a total score of six, which is close to the median value of the ranges seen in Table 6-3, with a high score of eleven. Using a value of six as the basis for selection, 28 subwatersheds were identified for Detailed Assessment. Figure 6-2 shows that the majority of the degraded subwatersheds are located in the upper portions of the study area. Only three of the Bear Creek HU subwatersheds were determined to be functionally deficient, primarily due to nutrient loading concerns. Since only MR08 and MR07 have any significant imperviousness, agricultural activities are generally the primary sources of the stressors. During the Detailed Assessment phase, field work will be undertaken at a select subset of sites to investigate existing agricultural BMPs and determine if and what type of improvements should be made. 6-7 Upper Rocky River Preliminary Findings Report February 2005 Table 6-3. LWP Subwatersheds Scoring Results Subwatershed Number MR07 MR08 MR20 UR01 UR02 UR07 UR12 MR01 MR03 UR14 BC08 MR04 MR21 UR06 UR09 UR11 MR10 UR03 UR08 MR11 BC06 BC10 MR02 MR06 MR09 MR14 UR05 UR10 Sediment Loading 0 1 3 3 2 3 3 3 3 3 1 1 3 2 3 3 3 2 2 2 0 1 3 1 2 2 2 2 Total Total Buffer Nitrogen Phosphorous Imperviousness Disturbance Loading Loading 3 3 2 3 3 3 2 2 2 1 3 3 1 3 2 1 2 2 2 1 3 2 1 1 0 0 1 1 3 3 3 3 3 3 3 2 3 3 2 3 2 3 2 3 3 2 2 2 2 1 2 1 1 1 2 2 2 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 2 3 2 3 2 3 3 2 3 3 2 3 1 2 2 0 2 2 2 1 2 0 3 3 3 1 1 Subwatershed Central Siler City Lower Loves Creek Middle Tick Creek 1 Rocky River Headwaters Liberty South Middle North Prong Johnson Creek Middle Rocky River 1 Rufus Brewer Upper Rocky River Mouth Sandy Branch Siler City North Middle Tick Creek 2 North Prong Headwaters Lower Greenbriar Creek Mud Lick Creek Upper Varnell Creek Rocky River at Staley Upper Greenbriar Creek Middle Varnell Creek Bear Creek Tributary 5 Upper Little Bear Creek Nick Creek Upper Loves Creek Middle Rocky River 3 Upper Meadow Creek Piney Grove Church Rocky River Reservoir Total Score 11 11 11 11 11 11 11 10 10 10 9 9 9 9 9 9 8 8 8 7 6 6 6 6 6 6 6 6 6-8 Upper Rocky River Preliminary Findings Report February 2005 Subwatershed Bear Creek Tributary 2 Middle Bear Creek 1 Middle Bear Creek 2 Lower Meadow Creek Upper Tick Creek Lacy Creek Lower Little Bear Creek Middle Rocky River 2 Tick Creek Tributary Staley South Bear Creek Tributary 1 Bear Creek Tributary 4 Middle Bear Creek 3 Lower Varnell Creek Lower Tick Creek Upper Bear Creek Bear Creek Tributary 3 Harts Creek Middle Rocky River 4 Middle Rocky River 5 Welch Creek Lower Bear Creek Subwatershed Number BC03 BC07 BC09 MR15 MR17 UR13 BC11 MR05 MR18 UR04 BC02 BC05 BC12 MR12 MR22 BC01 BC04 BC14 MR13 MR16 MR19 BC13 Sediment Loading 0 0 0 2 2 3 0 2 1 1 0 0 0 1 1 0 0 0 1 1 1 0 Total Total Buffer Nitrogen Phosphorous Imperviousness Disturbance Loading Loading 3 3 3 0 1 0 3 0 0 2 1 1 2 0 0 1 0 1 0 0 0 0 1 1 1 0 1 2 1 1 0 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 3 1 0 0 1 3 0 2 1 0 0 1 0 1 0 0 0 0 0 Total Score 5 5 5 5 5 5 4 4 4 4 3 2 2 2 2 1 1 1 1 1 1 0 6.3 PREPARING FOR DETAILED ASSESSMENT OF PRESERVATION OPPORTUNITIES Based on the scores presented in Table 4-7, subwatersheds in the Bear Creek HU have the most pristine existing conditions overall, warranting preservation efforts. Subwatersheds BC01, BC02, BC04, BC05, BC06 and BC08 are located in the upper portions of the Bear Creek HU and have the highest associated habitat preservation scores in the HU. The elevated scores can be attributed to high occurrences of forest and wetlands, and several Significant Natural Heritage Area locations. MR12 and MR18 in the Middle Rocky River HU had good priority scores as well, with high percentages of forest cover and wetland content. 6-9 Upper Rocky River Preliminary Findings Report February 2005 Sandy Branch (BC08) and Bear Creek Tributary 5 (BR06) had good priority scores and were also selected as target subwatersheds for Detailed Assessment due to their increased potential for nutrient delivery to local stream systems. A combination of preservation and restoration practices will be addressed in these subwatersheds. Subwatersheds UR08, UR11, UR13, MR10 and MR20 had the next highest priority scores with associated potential functional deficits. For the next phase of the process, field work will include investigating modeling results to verify the preservation potential within each subwatershed, and BEHI and habitat assessment surveys to determine which of the subwatersheds have the highest quality riparian corridor condition. Subwatersheds will be ranked according to their respective habitat assessment and BEHI scores to identify those subwatersheds that would benefit the most from preservation. Specific sites will be recommended in the Detailed Assessment for preservation based on the results of the preliminary assessment and field reviews. The basis for the parcels selected for preservation will be further explained in the Detailed Assessment as well. 6-10 Upper Rocky River Preliminary Findings Report February 2005 Figure 6-2. Targeted LWP Subwatersheds for Restoration and Management 6-11 Upper Rocky River Preliminary Findings Report February 2005 6-12 Upper Rocky River Preliminary Findings Report February 2005 7 Indicators and Assessment Tools Given the Detailed Assessment objectives and the primary stressors of concern, the following sections outline the indicators and assessment tools that will be used to conduct the Detailed Assessment and Management Report. Although not specifically addressed in the Detailed Assessment, bacteria concerns in the study area will be addressed qualitatively in the next phase of the process. Agricultural practices that affect sediment and nutrient loadings also have a secondary affect on bacteria reduction. 7.1 INSTREAM STRESSORS OF HYDROLOGIC AND AQUATIC HABITAT FUNCTIONS Stressors: Erosive stream velocities, increased sediment in streambed from bank erosion Indicators Streambank Condition Stream Condition Channel Stability Assessment Tool(s) BEHI from Field Surveys NCDWQ Habitat Assessment Field Data Sheet Allowable velocity from sediment competency calculations, field bankfull indicators Streambank condition will be evaluated using the bank erosion hazard index (BEHI) method (Rosgen, 2001), which is based upon channel evaluation methodologies of Pfankuch (1978). The BEHI evaluates key streambank characteristics sensitive to the various processes of erosion including: bank height ratio (streambank height/maximum bankfull depth), ratio of rooting depth/bank height, rooting density, percent surface area of bank protected, bank angle, number and location of various soil composition layers or lenses in the bank, and bank material composition. The BEHI values are converted to a risk rating of very low, low, moderate, high, very high, and extreme potential erodibility. BEHI ratings can be calculated for different vegetative cover scenarios that would reflect the implementation of various BMPs including cattle exclusion from streambank areas. The NCDWQ Habitat Assessment Field Data Sheet (NCDWQ, 2003b) is an adaptation of the USEPA Rapid Bioassessment Protocol and is intended as a quick and basic assessment protocol for stream health evaluation based on readily observable data. The protocol summarizes and provides assessment scores for characteristics relating to channel condition and stability, habitat, and riparian zone condition. An overall score is obtained as the total score divided by the number of individual assessments scored. A variety of quantitative approaches exist to predict channel stability. These approaches generally utilize stream velocity, shear stress, and stream power. These methods are summarized in SCS (1977), USACE (1994), and FISWRG (1998). A useful assessment tool is found in the allowable stream velocity-depth relationships developed by USDA-SCS (1977) for the design of open channels. The relationships were based on empirical data that provide for both cohesive and non-cohesive materials. For cohesive materials in the sand-clay range, allowable velocities are approximately 4.2 fps at channel forming flows. These values increase with depth. Storm events where stream velocities exceed critical velocities for a given bed material are likely to result in channel erosion. Channel-forming flow is often considered to be synonymous with bankfull discharge. Stream velocities at bankfull discharge can be estimated from Manning’s equation using field-derived estimates of bankfull height as follows: 7-1 Upper Rocky River Preliminary Findings Report February 2005 V= θ n R S 2 3 1 2 where θ = 1.49 for U.S. units or 1.0 for metric units, n is the Manning’s roughness coefficient for bankfull conditions, R = the hydraulic radius associated with bankfull depth and width, and S = slope. The average boundary shear stress on the cross section can be estimated from: τ = γRS where γ = specific weight of water; R and S are defined above. Brookes (1990) suggested the product of bankfull velocity and shear stress, which is equivalent to stream power per unit bed area, as a practical criterion for stream restoration initiatives. Streams with powers less than 1.0 lb/sec/ft2 generally failed through deposition and aggradation, while streams with powers greater than 3.4 lb/sec/ft2 failed due to erosion. Streams where power ranged from 1.0 to 3.4 lb/sec/ft2 at channel forming flow are generally in a state of dynamic equilibrium. The rate of change in stream power or critical velocity is a significant indicator of more generalized patterns of erosion or deposition along a stream reach. A stream reach that exceeds the critical threshold, and shows a pattern of increasing stream power with decreasing channel elevation, is likely to be consistently erosional along its length. Conversely, a stream reach that exceeds critical thresholds at channel-forming flows but shows a pattern of decreasing power may experience deposition of coarser particles in downstream areas. These analyses will provide a relative measure of expected changes in stream stability accompanying changes in land use and implementation of best management practices. Static hydrologic modeling, utilizing stream channel cross section, slope, and bankfull height will allow for an evaluation of the current vulnerability of a stream reach to instability resulting from sediment aggradation/degradation. Existing rating curves for rural piedmont streams can be combined with field surveys to verify bank full stage, calculate stream velocities, and estimate shear stress and stream power during bank full events. It should also be noted that the specific stream power and critical velocity criteria presented here are not appropriate for all stream types. These criteria were developed for low-medium gradient alluvial channels, typical of most streams in the North Carolina Piedmont. Conversely, they are not appropriate for high gradient colluvial streams typical of the step-pool systems found in the mountains and foothills of North Carolina. The BEHI surveys and habitat assessments will be compiled in the Detailed Assessment and compared with respect to preservation and restoration potential. Scores will be tabulated and those subwatersheds determined to have the best potential for restoration and/or preservation will be identified. Field assessment techniques will be the same for subwatersheds slated for preservation and for restoration. Although the field gathering techniques are the same, the data will be used differently. For subwatersheds slated for preservation potential, the results of the habitat assessment will be used to determine which of the subwatersheds have the highest existing water quality. Therefore, habitat is intended to be the measure of water quality within the study area based on the results of the field work. Once the subwatersheds with the highest existing water quality, according to the field assessment, have been identified, specific parcels within those subwatersheds will be selected that would have the greatest watershed benefits from preservation. Based on the results of the preliminary characterization for preservation potential, sites for field work are shown in Figure 7-1. For restoration sites, the field data will be compiled and those subwatersheds that have the lowest combined scores will be identified as having the highest levels of stress. The field data will also help in determining the accuracy of the predictive models to actual conditions. Once the functional deficits have been further quantified and subwatersheds with the greatest potential for degradation have been selected, specific parcels that are located in areas that could potentially be used as a restoration, management or 7-2 Upper Rocky River Preliminary Findings Report February 2005 BMP retrofit site will be identified in urban areas. The recommended management practice to alleviate the associated stressors will also be provided, with associated levels of stress reduction based on the type of management practice recommended. For rural areas, agricultural BMPs will be recommended on a watershed scale, providing general information regarding practices that could alleviate excessive nutrient and sediment loadings to local streams. Field locations selected for Detailed Assessment of potential restoration sites are shown in Figure 7-2. 7-3 Upper Rocky River Preliminary Findings Report February 2005 Liberty UR06 UR07 UR02 UR03 UR08 [ % UR09 UR12 UR11 UR01 UR10 UR05 UR14 UR13 MR02 MR03 MR01 MR04 MR07 MR08 Siler City MR05 MR12 Staley UR04 [ % MR10 MR09 [ % [ % MR13 [ % MR15 MR11 [ % MR06 MR14 MR19 MR16 [ % % [ [ % MR22 BC10 BC11 BC14 BC12 BC13 MR18 MR21 [ % [ % MR17 [ % [ MR20 % BC05 BC08 BC06 [ % BC01 [ % N [ % [ % BC02 BC 04 BC04 [ % [ % [ % BC09 [ % BC07 [ % [ [ % % 0 2 4 Miles BC03 2 [ % Stream Assessment Sites with Preservation Potential NW I Wetlands Subwatershed Boundaries USGS 1:24,000 K Hydrography Perennial Streams Intermittent Streams Waterbodies Municipalities County Boundaries Major Roads Figure 7-1. Field Site Locations within Targeted Subwatersheds for Preservation Opportunities 7-4 Upper Rocky River Preliminary Findings Report February 2005 Liberty UR06 [ % UR01 [ % UR09 [ % [ [ % % % UR02 [ % [ [ % UR12 UR11 [ % [ [ % % [ % UR10 UR03 [ % UR05 Staley [ % [ % UR04 [ % UR14 MR02 UR07 UR13 MR01 MR04 Siler City MR07 [ % [ % UR08 [ % [ % MR10 [ % [ [ % % [ % MR03 [ % MR05 MR12 MR11 MR13 MR16 MR15 MR21 [ % [ % [ [ % % [ % [ % MR06 [ % MR19 MR18 MR17 MR08 MR09 MR14 MR20 BC05 [ % MR22 BC10 BC11 BC09 BC14 BC12 BC13 BC08 BC06 BC01 BC 04 BC0 4 N BC02 BC07 BC03 2 0 2 4 Miles [ % Stream Assessment Sites with Restoration Potential NW I Wetlands Subwatershed Boundaries USGS 1:24,000 K Hydrography Perennial Streams Intermittent Streams Waterbodies Municipalities County Boundaries Major Roads Figure 7-2. Field Site Locations within Targeted Subwatersheds for Restoration and Management 7-5 Upper Rocky River Preliminary Findings Report February 2005 7.2 NUTRIENT LOADING AND EUTROPHICATION STRESSORS OF WATER QUALITY AND HABITAT FUNCTIONS Stressors: Nutrient loading and eutrophication Indicators Existing nonpoint nutrient loads Chlorophyll-a concentration Assessment Tool(s) GWLF loading model BATHTUB model As discussed in Section 4.2, a draft nonpoint source nutrient loading model was developed for all of the study area. The GWLF model was applied to assess nutrient loading from the study area using a parcellevel analysis of land use. The model estimated nutrient loading and delivery at the subwatershed level throughout the study area. Properties in the northern portion of the study area above the Rocky River Reservoir that drain to the reservoir are of particular concern based on the recent hypereutrophic conditions noted by DWQ in 2003. For the Detailed Assessment, subwatersheds that ranked high for nutrient loading based on the scoring system described in Section 6.2 will be evaluated to determine what types of management practices are most applicable. For rural agricultural areas, field reconnaissance will be performed at select sites to identify potential upland BMP opportunities based on common practices. Urban areas with high potential to deliver nutrients to local stream systems will be evaluated for urban BMP retrofits and stream restorations depending on the primary stressors associated with the functional deficits. Once the appropriate management measure has been identified on a specific parcel, benefits of the measure will be quantified based on expected reduction in loads to area streams from the recommended practice. The BATHTUB model will be used to estimate the improvement of in-lake chlorophyll-a concentrations based on the reduction of area loadings. Data required for the model will be acquired during the Detailed Assessment phase and is listed in Section 8.2. The BATHTUB model applies a series of empirical eutrophication models to morphologically complex lakes and reservoirs. The program performs steady-state water and nutrient balance calculations in a spatially segmented hydraulic network, which accounts for advective and diffusive transport, and nutrient sedimentation. Eutrophication-related water quality conditions (total phosphorus, total nitrogen, chlorophyll-a, transparency, and hypolimnetic oxygen depletion) are predicted using empirical relationships derived from assessments of reservoir data. 7.3 RIPARIAN CORRIDOR STRESSORS OF HYDROLOGY AND WATER QUALITY FUNCTIONS Stressors: Riparian buffer disturbance and wetland loss Indicators Riparian Buffer Disturbance Stream Condition Detailed Field Evaluations Assessment Tool(s) GIS Analysis, Aerial Imagery, Field Survey BEHI from Field Surveys Habitat Assessment Field Data Sheet Field Survey 7-6 Upper Rocky River Preliminary Findings Report February 2005 Stream segments in which riparian buffer vegetation has been subject to significant loss or disturbance have a much higher vulnerability to stream instability. The analysis of buffer disturbance presented in Section 4.3 will serve as one basis for further field investigations. Stream segments in which the buffer disturbance is confirmed by aerial images will be scheduled for field survey to assess their condition. Stream conditions will be evaluated using in-situ assessment tools such as BEHI and habitat assessment measurements mentioned earlier in this chapter. Habitat scores will be used as a gage of existing water quality within the study area. BEHI scores are intended to aid in the validation of the erosion risk analysis performed earlier in this report and to rank stream segments based on existing conditions. The methods were discussed in more detail in Section 6. The Detailed Assessment will provide specific management measures to restore lost riparian corridors. Field identification of potential wetland restoration sites will involve confirmation of results from GIS based targeting procedures. This assessment will confirm the potential for creation of appropriate wetland hydrology (defined by reference wetlands), provide evidence of past or current presence of hydric soils, and assess local wetland plant seed banks. The detailed assessment of wetland hydrology will include a simple water budget using GIS analysis of annual hydrologic delivery from upland areas, annual evapotranspiration rates, and annual rates of groundwater infiltration based upon soil permeability. Further assessment of hydrology, including prediction of water levels, will depend on wetland design and should be included in site-specific wetland restoration plans from future contractors. 7-7 Upper Rocky River Preliminary Findings Report February 2005 (This page left intentionally blank.) 7-8 Upper Rocky River Preliminary Findings Report February 2005 8 Additional Data Needs 8.1 MONITORING DATA REQUIREMENTS The purpose of this section is to identify additional data needed to complete detailed assessment and development of local watershed plans for the study area watersheds. The availability of data in these watersheds is generally sparse. Standard GIS coverages for soils, land use, wetland areas, and aerial photography are available from federal sources. However, this information is generally 7 to 10 or more years old and is of a spatial resolution that is of limited value in assessment of conditions in long, narrow riparian corridors. Biological monitoring data is also quite limited. The North Carolina Division of Water Quality has collected a set of water quality monitoring data that has been quite useful in a scoping level assessment of the watershed. However, the limited number of sampling dates allows only cursory characterization of water quality conditions within the study area. Additional data needs for this study fall into three primary categories: • Data required for geomorphological characterization of stream channels and assessment of channel stability. • Biological and chemical monitoring data required for assessing use support within the study watersheds. • Water chemistry and channel morphology data required that can identify the sources of biological and water quality impairment. The primary objective of additional monitoring is to assess the effect of land use patterns and agricultural practices on water quality and biological community support in local streams. The primary water quality issue is sediment loading from both upland and streambank erosion. Both sediment sources are linked to agriculture and pasture management issues. Urban areas contribute to streambank erosion due to increased flows. Nutrient loading to area streams is an issue of concern in areas receiving land application of chicken manure and in areas where cattle deposit manure onto pastures and directly into stream channels. Fecal coliform bacteria loading from both chicken and cattle manure is a third issue of concern. Water quality issues related to residential and urban land uses are to be examined in several small watersheds in the middle portions of the study area, particularly around Siler City. In general, the existing DWQ sampling station locations fit nicely with the analysis of the study area. To preserve continuity with the existing DWQ data set, we have chosen a subset of DWQ stations (Table 8-1) and added a “reference” monitoring station on Bear Creek. The importance of storm events in nutrient and sediment export from these watersheds is likely to be high. We propose a combination of monthly ambient sampling with storm peak samples. Storm peak samples should be taken either as multiple grab samples at each station, or preferably with automatic samplers. Table 8-2 lists water quality parameters and corresponding EPA method codes. A meeting was conducted in August 2004 between representatives of Tetra Tech, NC DENR Regional Office staff and the EEP to review the draft monitoring plan for the Rocky River watershed. The draft plan is included as Appendix E. 8-1 Upper Rocky River Preliminary Findings Report Table 8-1. February 2005 A Summary of Proposed Stations of Additional Water Quality Monitoring Including Several Established NCDWQ Stations Drainage Area (sq. miles) 7.4 9 7 11 65 7.5 8 90 15.5 140 10.5 50 Chemical/Physical1 BF X X X X X X X X X X X X X X X X X SF X X Monitoring Location Rocky River at SR 1300 (Staley Snow Camp Rd) (USGS Gage) N. Pr. Rocky R SR 1300 Greenbrier Cr SR 1346 (Silk Hope Liberty Rd) Mud Lick Cr SR 1355 (R C Overman Rd) Rocky River at US 64 Loves Creek above WWTP near SR 2203 (Waste Treatment Plant Rd) Varnell Cr at SR 1503 (Stage Coach Rd) Rocky River at SR 2170 (Rives Chapel Ch. Rd) Tick Cr at SR 2120 (Ike Brooks Rd) (USGS Gage) Rocky River at NC 902 Bear Creek at SR 1141 (Edwards Hill Church Rd) Bear Creek at SR 2155 (Mays Chapel Rd) Notes: 1 Upstream Land Use Mostly agriculture plus urban Mostly agriculture Mostly agriculture Mostly agriculture Ag plus urban, commercial, residential Urban, commercial, residential Agriculture plus forest All land uses Ag, plus suburban, residential Ag plus urban, commercial, residential Forest plus agriculture Agriculture plus forest X indicates proposed monitoring to be undertaken as part of this assessment. BF = Baseflow Samples, SF = Stormflow samples 8-2 Upper Rocky River Preliminary Findings Report Table 8-2. Recommended Water Quality Parameters for Additional Monitoring EPA Method1 600/8-78-017 160.2 180.1 350.1 and 350.2 350.1 and 351.2 353.2 365.1 200.8/213.2 200.8/200.7 200.8/220.2 200.8/200.7 200.8/239.2 200.8/200.7 200.7 200.7 200.7 200.7 200.8/206.2 APHA Method2 9222D 2540D 2130B QUIK CHEM 10-107­ 06-1-J QUIK CHEM 10-107­ 06-2-H QUIK CHEM 10-107­ 04-1-C QUIK CHEM 10-115­ 01-1-EF February 2005 Parameter Coliform, MF fecal Susp. residue Turbidity NH3 as N TKN as N NO2+ NO3 as N P total as P Cadmium (Cd) Chromium (Cr) Copper (Cu) Nickel (Ni) Lead (Pb) Zinc (Zn) Aluminum (Al) Calcium (Ca) Iron (Fe) Magnesium (Mg) Arsenic (As) 1 2 Other Method PQL 1 colony/100mL 2 mg/L 1 NTU 0.01 mg/L 0.20 mg/L 0.01 mg/L 0.02 mg/L 2.0 µg/L 25 µg/L 2.0 µg/L 10 µg/L 10 µg/L 10 µg/L 50 µg/L 0.10 mg/L 50 µg/L 0.10 mg/L 10 µg/L Revision Date 3/13/01 3/13/01 3/13/01 7/24/01 7/24/01 7/24/01 7/24/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 US Environmental Protection Agency Method American Public Health Association Method 8.1.1 Water Quality Parameters Water quality parameters were selected from among the suite of standard WARP monitoring parameters. The parameters were selected to assess relationships between land use patterns and nutrient, sediment, and fecal coliform bacteria concentrations. This dataset will also provide a baseline for assessment of future changes in stream water quality. Collection of field parameters (dissolved oxygen, specific conductance, pH, and water temperature) is recommended for all stations. Samples will be collected for laboratory analysis of nutrients (total phosphorus, ammonia, TKN and nitrite-nitrate), suspended residue, turbidity, metals, and fecal coliform. Table 8-2 contains a complete parameter listing. Toxicity testing is planned for Loves Creek due to its impaired status by DWQ. At other locations, toxicity testing and other parameters (i.e., BOD, pesticides) may be evaluated if conditions warrant and if resources allow. 8-3 Upper Rocky River Preliminary Findings Report February 2005 8.1.2 Stream Channel Geomorphology and Benthic Habitat Data Requirements Geomorphological assessment will be performed on a selected set of stream reaches throughout the study area. The scoping level model of stream reach stability will be used in conjunction with aerial photographs to select stream reaches for assessment and will include reference reaches, reaches close to monitoring stations, and reaches representative of moderate and high levels of erosion potential grouped by stream order. Measures of channel characteristics will include stream class, slope, shape, channel cross section, dominant texture class, riparian vegetation, flow regime, woody debris characterization, stream size and order, streambank erosion potential (BEHI), and channel stability rating. Geomorphological data will be collected using techniques described by Rosgen (1996) and using field data sheets produced by Wildland Hydrology, Inc. and those included in Kuhnle and Simon (2000). Stream habitat assessment will be performed using the North Carolina Habitat Assessment Field Data Sheet for Mountain/Piedmont Streams (NCDWQ, 2003). This method is a regional adaptation of the USEPA Rapid Biological Assessment Protocol (RBP). The stream habitat parameters cover various aspects of the stream and riparian environment including in-stream habitat, channel morphology, bank structural features, and riparian vegetation. 8.2 MODELING DATA REQUIREMENTS For the Detailed Assessment, the only additional modeling expected to occur is the BATHTUB model for the Rocky River Reservoir. Input data includes information describing watershed characteristics, water and nutrient loads, and reservoir morphology. Output from the GWLF model used during this preliminary characterization will be used for the water and nutrient load input and data assembled regarding watershed characteristics from available GIS data will be used for the model. Once management benefits have been quantified, new inputs for water and nutrient loadings will be generated to provide a measure of the overall affect of the management measures. The only missing data required to run the BATHTUB model is reservoir morphology. Since the Rocky River Reservoir is a water supply, data regarding bathymetry should be readily available from the Town of Siler City or the North Carolina Division of Water Resources. Results from the model will quantify restoration and management benefits from implementing the recommended practices set forth in the Detailed Assessment. 8-4 Upper Rocky River Preliminary Findings Report February 2005 9 References Alamance County. 2003. Alamance County Destination 2020: Charting a Course to Alamance County’s Future. Alamance County Planning Department and Glenn Harbeck Associates. April 2003. Beaulac, M.N. and K.H. Reckhow. 1982. An examination of land use and nutrient export relationships. Water Resources Bulletin, 18: 1013. Brooks, A. 1990. Restoration and Enhancement of Engineered River Channels: Some European Experiences. Regulated Rivers: Research and Management, 5 (1): 45-56. Cadmus. 1995. Falls Lake Watershed Study - Final Report. Prepared for NC DEHNR by The Cadmus Group, Inc., Durham, NC. October 1995. Cadmus. 1996. Cane Creek Reservoir Watershed Study – Draft Report. Prepared for Orange Water and Sewer Authority by The Cadmus Group, Inc., Durham, NC. August 1996. CH2M HILL. 2000. Urban Stormwater Pollutant Assessment. Prepared for NC DENR, Division of Water Quality, August 8, 2000. Chatham County. 2001. Land Use Development Plan. Chatham County Planning Office. November 2001. Dai, T. and R.L. Wetzel. 1999. BasinSim 1.0, A Windows-Based Watershed Modeling Package, User’s Guide. Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA. Dodd, R.C. and J.P. Tippett. 1994. Nutrient Modeling and Management in the Tar-Pamlico River Basin. Prepared for N.C. Division of Environmental Management. Research Triangle Institute, Research Triangle Park, NC. Evans, B.M., D.W. Lehning, K.J. Corradini, G.W. Petersen, E. Nizeyimana, J.M. Hamlett, P.D. Robillard, and R.L. Day. 2002. A comprehensive GIS-based modeling approach for predicting nutrient loads in watersheds. Journal of Spatial Hydrology, 2(2): 1-18. FEMA. 1996. Digital Flood Data derived from Digital Flood Insurance Rate Map (DFIRM). Federal Emergency Management Agency, Mitigation Directorate, Q3 Flood Data Program. 500 C Street, SW, Washington, D.C. 20472. Data obtained 2003 though N.C. Department of Transportation. http://www.ncdot.org/planning/statewide/gis/DataDist/DataDist.html FISWRG. 1998. Stream Corridor Restoration: Principles, Processes, and Practices. Federal Interagency Stream Restoration Work Group. Frink, C.R. 1991. Estimating nutrient export to estuaries. Journal of Environmental Quality, 20: 717-724. Greensboro. 2003. Storm Event Monitoring Summary Report, 1995-1999. City of Greensboro, NC. Groce, Sam. 2004. Personal Communication. North Carolina State University Cooperative Extension Agent. Haith, D.A. and D.E. Merrill. 1987. Evaluation of a daily rainfall erosivity model. Transactions of the American Society of Agricultural Engineers, 30(1): 90-93. Haith, D.A., R. Mandel, and R.S. Wu. 1992. GWLF, Generalized Watershed Loading Functions, Version 2.0: User’s Manual. Department of Agricultural and Biological Engineering, Cornell University, Ithaca, NY. Hall, S. and Boyer, M. 1992. Inventory of Natural Areas and Wildlife Habitats of Chatham County, North Carolina. North Carolina Department of Environment and Natural Resources, NC Division of Parks and Recreation, NC Heritage Program. 9-1 Upper Rocky River Preliminary Findings Report February 2005 Hall, S., and Pearsall, L. NC Natural Heritage Program. 2004. Personal Communication. Meeting to Coordinate and Obtain Input from Representatives of Wildlife Habitat and Natural Resource Agencies. Offices of NC Ecosystem Enhancement Program, January, 2004. Hartigan, J.P., T.F. Quasebarth, and E. Southerland. 1983. Calibration of NPS model loading factors. Journal of Environmental Engineering, 109(6): 1259-1272. Howarth, R.W., J.R. Fruci, and D. Sherman. 1991. Inputs of sediment and carbon to an estuarine ecosystem: Influence of land use. Ecological Applications, 1:27-39. Karr, J.R, 1981, Assessment of biotic integrity using fish communities: Fisheries, v.6, p. 21-27. Karr, J.R., Fausch, K.D., Angermeier, P.L., Yant, P.R., and Schlosser, I.J., 1986, Assessing biological integrity in running waters-- a method and its rationale: Illinois Natural History Survey Special Publication Number 5, 28 p. Kuhnle, R.A. and A. Simon. 2000. Evaluation of Sediment Transport Data for Clean Sediment TMDL's. United States Department of Agriculture, National Sedimentation Laboratory Lee, K., T.R. Fisher, and E. Rochelle-Newell. 2001. Modeling the hydrochemistry of the Choptank River basin using GWLF and Arc/Info: 2. Model validation and application. Biogeochemistry, 56(3): 311-348. Line, D.E., N.M. White, D.L. Osmond, G.D. Jennings, and C.B. Mojonnier. 2002. Pollutant export from various land uses in the upper Neuse River basin. Water Environment Research, 74(1): 100-108. NCCGIA. 2002. BasinPro GIS data system Version 2.1. N.C. Center for Geographic Information and Analysis. Raleigh, N.C. 4 CD set. NCDENR. 1999. Basinwide Assessment Report for the Cape Fear River Basin. Environmental Sciences Branch. N.C. Department of Environment and Natural Resources – Division of Water Quality, June 1999. NCDENR. 2000. Cape Fear River Basinwide Water Quality Plan. N.C. Department of Environment and Natural Resources, Division of Water Quality, July 2000. NCDENR. 2003a. Standard Operating Procedures for Benthic Macroinvertebrates. Biological Assessment Unit. Environmental Sciences Branch. N.C. Department of Environment and Natural Resources – Division of Water Quality. July 2003. NCDENR. 2003b. North Carolina Natural Heritage Data. North Carolina Department of Natural Resources, Natural Heritage Program. http://www.ncnhp.org/Pages/heritagedata.html. NCDENR. 2004a. North Carolina Water Quality Assessment and Impaired Waters List (2004 Integrated 305(b) and 303(d) Report). Public Review Draft. N.C. Department of Environment and Natural Resources, April 2004. NCDENR. 2004b. Basinwide Assessment Report for the Cape Fear River Basin. Environmental Sciences Branch. N.C. Department of Environment and Natural Resources – Division of Water Quality, August 2004. NCDENR. 2004c. Summary of Existing Water Quality Data, Rocky River Watershed, Chatham County. Biological Assessment Unit. Environmental Sciences Branch. N.C. Department of Environment and Natural Resources – Division of Water Quality. February 2004. NCDWQ. 2001. Standard Operating Procedure Biological Monitoring – Stream Fish Community Assessment & Fish Tissue. N.C. Department of Environment and Natural Resources, March 2001. NCDWQ. 2004. Memorandum: From Jim Fisher to Jimmie Overton regarding Rocky River Survey Subbasin 03-06-12. March 24, 2004. 9-2 Upper Rocky River Preliminary Findings Report February 2005 NCEEP. 2003. Report from the Watershed Needs Assessment Team to the Mitigation Coordination Group. N.C. Ecosystem Enhancement Program, October 2003. NCGAP. 2003. NC Gap Analysis Project, 2003. Vegetation Data. [Online]. Available: http://www.ncgap.ncsu.edu/ NCSU. 2004. The North Carolina Nutrient Management Database System. North Carolina State University. http://arcims.soil.ncsu.edu/nutman/main.htm . Novotny, V. and H. Olem. 1994. Water Quality: Prevention, Identification, and Management of Diffuse Pollution. Van Nostrand Reinhold, New York. NWI. 1994. National Wetlands Inventory. U.S. Fish & Wildlife Service. United States Department of the Interior, Washington , D.C. USFWS. 1999. National Wetlands Inventory website. US Department of the Interior, Fish and Wildlife Service, St. Petersburg, FL. http://www.nwi.fws.gov/index.html. Pfankuch, Dale 1978. Stream reach inventory and channel stability evaluation, a watershed management procedure. USDA Forest Service Northern Region R1-75-002. Govt. Printing Office, # 696-260/200, Wash. D.C. 26 pp. Randolph County. 2002. Randolph County Growth Management Plan. Randolph County Department of Planning and Development. February 2002. http://www.co.randolph.nc.us/planning_zoning/GMPAdotionResolution.htm . Renard, K.G., G.R. Foster, G.A. Weesies, D.K. McCool, and C. Yoder. 1997. Predicting Soil Erosion by Water: A Guide to Conservation Planning with the Revised Universal Soil Loss Equation (RUSLE). Agricultural Handbook 703. U.S. Department of Agriculture, Washington, DC. Rosgen, D.L. 1996. Applied River Morphology. Wildland Hydrology Books, Pagosa Springs, Colorado. Rosgen, P.H. 2001. A Practical Method of Computing Stream Bank Erosion. Wildland Hydrology Inc., Pagosa Springs, Colorado. Schueler. 2004. Urban Subwatershed Restoration Manual No. 1: An Integrated Framework to Restore Small Urban Watersheds version 1.0. Prepared for the Office of Water Management, USEPA, Washington, DC. Center for Watershed Protection, Ellicot, MD. SCS. 1977. National Engineering Handbook. Section 3, Chapter 6. United States Department of Agriculture, Soil Conservation Service, Washington D.C. SCS. 1986. Urban Hydrology for Small Watersheds. Technical Release 55. Soil Conservation Service, U.S. Department of Agriculture, Washington, DC. Schneiderman, E.M., D.C. Pierson, D.G. Lounsbury, and M.S. Zion. 2002. Modeling the hydrochemistry of the Cannonsville watershed with generalized watershed loading functions (GWLF). Journal of the American Water Resources Association, 38(3): 1323-1347. StatSoft. 1994. STATISTICA General Conventions and Statistics. Vol. I. StatSoft, Inc. Tulsa, Oklahoma. Swaney, D.P., D. Sherman, and R.W. Howarth. 1996. Modeling water, sediment and organic carbon discharges in the Hudson-Mohawk Basin: Coupling to terrestrial sources. Estuaries, 4: 833-847. Tetra Tech. 2000. Watershed Characterization System, Version 1.1. Prepared for U.S. EPA, Region 4. Tetra Tech, Inc., Fairfax, VA. Tetra Tech. 2003a. Technical Memorandum – Task 1: Impact Analysis, Town of Cary Project GG1053, Town Center Stormwater Management Plan. Prepared for the Town of Cary, NC. Tetra Tech, Inc., Research Triangle Park, NC. 9-3 Upper Rocky River Preliminary Findings Report February 2005 Tetra Tech. 2003b. B. Everett Jordan Lake Nutrient Response Model Enhancement. Prepared for N.C. Division of Water Quality. Tetra Tech, Inc., Research Triangle Park, NC. Tetra Tech. 2003c. Deep River Cataloging Unit Restoration Site Search Results Technical Memo. Prepared for N.C. Ecosystem Enhancement Program. Tetra Tech, Inc., Research Triangle Park, NC. Tetra Tech. 2004a. Upper Yadkin River Basin Detailed Assessment Report. Prepared for NC Ecosystem Enhancement Program. Tetra Tech, Inc., Research Triangle Park, NC. April 2004. Tetra Tech. 2004b. Morgan Creek LWP Detailed Assessment Report. Prepared for NC Ecosystem Enhancement Program. Tetra Tech, Inc., Research Triangle Park, NC. July 2004. Town of Siler City. 2003. Town of Siler City Land Development Plan. Town of Siler City Planning and Community Development. Triangle Land Conservancy. 2002. Triangle Green Print Regional Open Space Assessment. Prepared in association with Triangle J Council of Governments and Division of Parks and Recreation, N.C. Department of Environment and Natural Resources. February 2002. USACE. 1994. Channel Stability Assessment for Flood Control Projects. Report EM 1110-2-1418. U.S. Army Corps of Engineers, Washington, D.C. USDA SCS, 1977. Engineering Field Manual. US Department of Agriculture, Soil Conservation Service. US Government Printing Office, Washington DC. USDA-NRCS. 2002. Soil Survey of Randolph County, North Carolina. U.S. Department of Agriculture Natural Resource Conservation Service. US EPA. 1983. Results of the Nationwide Urban Runoff Program, Volume 1, Final Report. Water Planning Division, U.S. Environmental Protection Agency, Washington, DC. US EPA. 1992. National Land Cover Data Set. United States Environmental Protection Agency and the Multi-Resolution Land Consortium. http://www.epa.gov/mrlc.htm . USFWS. 1999. National Wetlands Inventory website. US Department of the Interior, Fish and Wildlife Service, St. Petersburg, FL. http://www.nwi.fws.gov/index/html USGS. 2000. National Land Cover Dataset. Fact Sheet 108-00. U.S. Geological Survey, Reston, VA. Wischmeier, W.H. and D.D. Smith. 1978. Predicting Rainfall Erosion Losses: A Guide to Conservation Planning. Agricultural Handbook 537. U.S. Department of Agriculture, Washington, DC. 9-4 Upper Rocky River Preliminary Findings Report February 2005 10 Appendices 10-1 Upper Rocky River Preliminary Findings Report February 2005 (This page left intentionally blank.) 10-2 Upper Rocky River Preliminary Findings Report February 2005 Appendix A. Rocky River GIS Catalog A-1 Upper Rocky River Preliminary Findings Report February 2005 (This page left intentionally blank.) A-2 Upper Rocky River Preliminary Findings Report Table A-1. Category Aerial Photographs Aerial Photographs Aerial Photographs Aerial Photographs Basinpro Buildings Census Census Conservation and Open Space County Boundaries February 2005 Rocky River GIS Catalogue Location Chatham County Chatham County Chatham County Chatham County North Carolina Chatham County North Carolina North Carolina Chatham County Chatham County File Name index400.shp mapindex.shp Description Index for 400 series Orthophotos, 2002 Index for higher resolution photos, 2002 Aerial image of entire county, spans most of the Rocky River study area, 2002 100, 200, and 400 series Aerial Photographs, 2002 Watersheds, infrastructure, monitoring, natural heritage, etc., 2002 Polygons of building footprints, 2004 1990 Census Tracks for North Carolina 1991 Census Block Groups for North Carolina Lands protected by Triangle Land Conservancy either via ownership or conservation easement, 2002 Chatham County boundary, 2002 These CAD files have detailed street, stream, and waterbody outlines (with some elevations), but no elevation contours, 2003 Parcels labeled with flood zones, designated by hand from paper FEMA maps, 2003 Projection sp83ft sp83ft Source Chatham County Chatham County Metadata Contact http://www.co.chatham.nc.us http://www.co.chatham.nc.us chath400.sid Multiple Files Multiple Files bldg.shp tr37_d90.shp bg37_d90.shp sp83ft sp83ft sp83m sp83ft dd­ NAD27 dd­ NAD27 Chatham County Chatham County BasinPro 2.1 Chatham County U.S. Census Bureau U.S. Census Bureau Triangle Land Conservancy; Orange County KCI http://www.co.chatham.nc.us Jeremy S. Poss http://www.cgia.state.nc.us/cgd b/datalist.html Jeremy S. Poss http://www.census.gov/geo/ww w/cob/index.html http://www.census.gov/geo/ww w/cob/index.html Doug Nicholas (TLC); Beth Young (Orange County) Kimberly Burton, Environmental Scientist and GIS Analyst tlc 2002.shp county_shp.shp sp83ft sp83ft DTM Chatham County Chatham County Multiple files sp83ft Chatham County Jeremy S. Poss FEMA flood_parcels.shp sp83ft Chatham County Jeremy S. Poss A-3 Upper Rocky River Preliminary Findings Report February 2005 Category GAP Geology Hydrography Hydrography Land Use/ Zoning Land Use/ Zoning Municipal Boundaries Location Deep River North Carolina Chatham County Chatham County Chatham County Chatham County Chatham County File Name gap03030003 Detailed_Geologi c.sid hydro_line.shp hydro_poly.shp Description Detailed vegetation cover data, 2003 Mr. Sid image of the North Carolina Geologic Map, 1998 County-wide hydrography lines with builtin legend, 2002 County-wide hydrography polygons with built-in legend, 2002 Water supply watersheds, only a portion of the county. Boundaries differ from "Final_wtshd.shp," 2002 Water supply watersheds, entire county. Boundaries differ from "wsw.shp," 2002 Extra-territorial Jurisdiction for Siler City and Pittsboro, 2002 Covers the entire extent of Chatham County and delineates 12 townships. County boundaries are slightly different from County_shp.shp, 2002 Limits of Siler City and Pittsboro, a polygon circle is drawn for Goldston, 2002 National Wetlands Inventory, 1999 Outlines of buildings in Chatham County, more extensive than Chat.bldg, 2002 Roads within Chatham County, 2002 Projection sp83m sp83m sp83ft sp83ft Source NC GAP Analysis Project NCCGIA KCI KCI Metadata Contact http://www.ncgap.ncsu.edu http://www.cgia.state.nc.us/cgd b/datalist.html Kimberly Burton, Environmental Scientist and GIS Analyst Kimberly Burton, Environmental Scientist and GIS Analyst Kimberly Burton, Environmental Scientist and GIS Analyst Kimberly Burton, Environmental Scientist and GIS Analyst Kimberly Burton, Environmental Scientist and GIS Analyst wsw.shp sp83ft KCI final_wtshd.shp etj.shp sp83ft sp83ft KCI KCI Municipal Boundaries Municipal Boundaries NWI Planimetrics Roads Chatham County Chatham County North Carolina Chatham County Chatham County townships.shp sp83ft KCI Kimberly Burton, Environmental Scientist and GIS Analyst Kimberly Burton, Environmental Scientist and GIS Analyst http://www.cgia.state.nc.us/cgd b/datalist.html Kimberly Burton, Environmental Scientist and GIS Analyst Kimberly Burton, Environmental Scientist and GIS Analyst limits.shp Multiple files bldg.shp roads.shp sp83ft sp83m sp83ft sp83ft KCI NCGIA KCI KCI A-4 Upper Rocky River Preliminary Findings Report February 2005 Category Location Chatham County File Name Description Sewer lines within Chatham County, same as sewer.shp from County GIS, 2002 Revised, merged STATSGO and available SSURGO data for Deep River CU, contains weighted K-factor, 2004 Projection Source Metadata Contact Kimberly Burton, Environmental Scientist and GIS Analyst Jason Doll Stantec Ph: (919) 851-6866 jcdoll@stantec.com Jason Doll Stantec Ph: (919) 851-6866 jcdoll@stantec.com Sewer Lines sewer.shp sp83ft KCI Soils Deep River Rocky River LWP Study Area Rocky River LWP Study Area Chatham County deepr_soils_kfact 2.shp rockyriv_subwater sheds_draft_sp 83m.shp ncsp83m Tetra Tech, Inc. Subwatersheds Draft subwatershed delineation, 2004 USGS DEM download seamlessly from USGS website, 2004 Chatham County water lines, most updated of files received and same as file from Chatham GIS, 2002 sp83m Tetra Tech, Inc. USGS-DEM 14134792 sp83m USGS http://seamless.usgs.gov/ Kimberly Burton, Environmental Scientist and GIS Analyst Water Lines wtrlines.shp sp83ft KCI A-5 Upper Rocky River Preliminary Findings Report February 2005 (This page left intentionally blank.) A-6 Upper Rocky River Preliminary Findings Report February 2005 Appendix B. Rocky River Imperviousness Estimation B-1 Upper Rocky River Preliminary Findings Report February 2005 (This page left intentionally blank.) B-2 Upper Rocky River Preliminary Findings Report February 2005 Approach Taken to Estimate Imperviousness per Subwatershed of the Rocky River Study Area Available Geographic Data The Rocky River LWP Study Area falls almost entirely within Chatham County, with small portions falling in Alamance and Randolph counties. For Chatham County, a number of recent GIS coverages are available which facilitate the calculation of estimated imperviousness: • Roadway centerlines • Driveways (developed for 911 services, this coverage does not include all driveways, but only the longer driveways in rural areas) • Building footprints • Tax parcels • Municipal boundaries • Zoning (for Siler City) • Aerial photography The above sources of information were used to develop estimates of imperviousness for 44 subwatersheds that were entirely or largely within Chatham County. The other six subwatersheds were either largely outside of Chatham County, or the portion that fell within Chatham County did not represent the state of development in the remaining portion, and so could not be used to extrapolate overall imperviousness. The GIS information available for Randolph and Alamance counties was less complete than for Chatham County, so it was not possible to take the same approach to calculating imperviousness here. Instead, results from the Chatham County subwatersheds were extrapolated via a simple regression model to estimate imperviousness for the final six subwatersheds. This is discussed in more detail below. Approach The approach taken for the Chatham County portion of the Rocky River study area was to use the available GIS coverages to generate estimates for total area of each of the following types of imperviousness: • • • • Buildings Driveways associated with residential buildings Parking lots associated with commercial/office/institutional buildings Roads The sum of the above was considered to be equal to total imperviousness. These results were then tabulated for each subwatershed, and divided by the total area of each subwatershed to yield percent imperviousness. Estimation of each of four categories of imperviousness is discussed in more detail in the following sections. Buildings Chatham County has a comprehensive GIS database of buildings, with each building having an assigned “building type,” such as “Commercial,” “Residential,” “School,” or “Church.” The completeness of the database allowed us to use it as a very good estimate of imperviousness generated by man-made structures. B-3 Upper Rocky River Preliminary Findings Report February 2005 Driveways / Parking Lots In addition, the buildings coverage was used as a basis for estimating the area of driveway and parking lot imperviousness. To this end, the “building type” field in the database was used to put all buildings into one of four more general categories: commercial (i.e., structures likely to have a parking lot, including multi-family residential structures), residential (i.e., single-family or duplex likely to have a driveway), mobile home, or other. For each building, its category determined the method used to estimate its associated driveway/parking lot impervious area, as discussed below. Driveways (“Residential”) As mentioned above, Chatham County has developed a “drives” GIS coverage, intended to help 911 services find their way to all buildings in the county. Short driveways found on small parcels are not in this database; it is mainly made up of longer driveways found in the more rural parts of the county. Based on a visual survey of aerial photos, these driveways tended to be dirt/gravel, and 8 to 12 feet in width. For the purposes of estimating impervious area, it was assumed that all driveways in this 911 drives coverage were 8 feet in width. (The lower end of the observed width range was used as a way of accounting for the somewhat reduced imperviousness of dirt/gravel roads as compared to paved roads.) For rural houses with driveways not in the 911 drives coverage, it was observed (in the parcels GIS coverage and I aerial photos) that almost all were quite close to a main road, with a driveway that went relatively directly from house to road. For these houses, therefore, a “nearest feature” analysis was done to calculate the distance from house to road for each house. This distance was assumed to be the length of the driveway for these houses. The width of these rural driveways was again assumed to be 8 feet. For the driveways of houses within the Siler City municipal boundary (the only urbanized portion of Chatham County within the study area), a regression model was used to estimate driveway area based on the building area and the size of the parcel. The regression model was developed by Tetra Tech using data from Mecklenburg County, and should be applicable to the similarly urban/suburban residential development of Siler City. The model was of the following form: ln [driveway area] = b0 + (b1)(ln [parcel area] ) + (b2)(ln [building area] ) or where driveway area = e(b0 + (b1)(ln [parcel area] ) + (b2)(ln [building area] )) areas are in square feet b0 = -0.249599 b1 = 0.374863 b2 = 0.475755. The parcel area is capped at five acres (217,800 sq square feet). Parking Lots (“Commercial”) There is a great range in the size of parking lots associated with “commercial” buildings. Based on the field reconnaissance and on a visual inspection of aerial photos, it was decided that, on average, the size of the parking lot was approximately equal to the footprint size of the structure itself. For the purposes of the imperviousness analysis, therefore, each building categorized as “commercial” was assumed to have an associated parking lot equal in area to the footprint of the building. B-4 Upper Rocky River Preliminary Findings Report February 2005 Mobile Homes Based on a visual inspection of aerial photos of mobile homes in both urban and rural areas of Chatham County, it was assumed that each mobile home had an associated parking area or driveway equal in area to the footprint of the home itself. Other Buildings placed in the “other” category included structures such as towers and barns. For these structures, no additional impervious area was assumed. Roads As mentioned above, a road centerlines coverage was available for Chatham County. In order to calculate imperviousness due to roads, it was necessary to assume a road width. In fact, road width varies a great deal, so it was decided that all roads should first be divided into several categories, each with an assumed width: • “City Commercial” streets were within Siler City limits, in areas zoned as non-residential (office, industrial, etc.) • “City Residential” streets were within Siler City, in areas with a residential zoning • “Major” was applied to US 64 as it passes through Siler City (otherwise known as Eleventh Street) • “Highway” was applied to US routes 64, 421 and 902 (except for the portion of US 64 assigned to “Major”) • “Rural” was applied to all remaining roads The average width of each of these categories of road was determined based on observation of aerial photos: Road Category City Commercial City Residential Major Highway Rural Width (feet) 40 24 4 6 28 24 (Note that there are portions of US 64 and US 421 that are divided highway, with a total width of 50 to 60 feet, but these are represented as two lines in the centerlines coverage, so the total width will be properly represented as two times 28 feet.) Extrapolation to the Six Non-Chatham County Subwatersheds The Middle North Prong and Lower Greenbriar Creek subwatersheds have areas outside of Chatham County, but the general development character of these areas seems to be in keeping with the rural character of the Chatham County portions, so for these two subwatersheds, the percent imperviousness calculated for the Chatham County portion was assumed to be applicable to the whole. There were six subwatersheds of the Rocky River LWP study area that could not be properly represented by the Chatham County portion, either because they lay entirely or largely outside of Chatham County, or because the portion of the subwatershed outside of Chatham County contained more urbanized areas B-5 Upper Rocky River Preliminary Findings Report February 2005 (parts of Liberty of Straley). In order to estimate percent imperviousness for these six subwatersheds, a simple regression model was developed using the other 44 subwatersheds to relate percent imperviousness to development character. Specifically, the subwatershed impervious ratio was regressed on the ratio of each subwatershed falling outside a municipal boundary (i.e., the “non-urban ratio”). The result is shown in Figure B-1. Based on this regression, it can be seen that urbanization is a good predictor of imperviousness for these subwatersheds. The derived regression equation was then used to calculate the impervious ratio of the remaining six subwatersheds. Regression of Impervious Ratio on Non-Urban Ratio per Subwatershed 20.00% 18.00% 16.00% Impervious Ratio 14.00% 12.00% 10.00% 8.00% 6.00% 4.00% 2.00% 0.00% 0 0.2 0.4 0.6 Non-Urban Ratio 0.8 1 1.2 y = -0.2029x + 0.2179 R2 = 0.9568 Figure B-1. Regression of Impervious Ratio on Non-Urban Ratio per Subwatershed B-6 Upper Rocky River Preliminary Findings Report February 2005 Appendix C. GWLF Watershed Model Development C-1 Upper Rocky River Preliminary Findings Report February 2005 (This page left intentionally blank.) C-2 Upper Rocky River Preliminary Findings Report February 2005 The GWLF Model GWLF simulates runoff and streamflow by a water-balance method, based on measurements of daily precipitation and average temperature. Precipitation is partitioned into direct runoff and infiltration using a form of the Natural Resources Conservation Service’s (NRCS) Curve Number method. The Curve Number determines the amount of precipitation that runs off directly, adjusted for antecedent soil moisture based on total precipitation in the preceding five days. A separate Curve Number is specified for each land use by hydrologic soil grouping. Infiltrated water is first assigned to unsaturated zone storage, where it may be lost through evapotranspiration. When storage in the unsaturated zone exceeds soil water capacity, the excess percolates to the shallow saturated zone. This zone is treated as a linear reservoir that discharges to the stream or loses moisture to deep seepage, at a rate described by the product of the zone’s moisture storage and a constant rate coefficient. Flow in rural streams may derive from surface runoff during precipitation events or from groundwater pathways. The amount of water available to the shallow groundwater zone is strongly affected by evapotranspiration, which GWLF estimates from available moisture in the unsaturated zone, potential evapotranspiration, and a cover coefficient. Potential evapotranspiration is estimated from a relationship to mean daily temperature and the number of daylight hours. Monthly sediment delivery from each land use is computed from erosion and the transport capacity of runoff, whereas total erosion is based on the universal soil loss equation, USLE (Wischmeier and Smith, 1978), with a modified rainfall erosivity coefficient that accounts for the precipitation energy available to detach soil particles (Haith and Merrill, 1987). Thus, erosion can occur when there is precipitation, but no surface runoff to the stream; delivery of sediment, however, depends on surface runoff volume. Sediment available for delivery is accumulated over a year, although excess sediment supply is not assumed to carry over from one year to the next. It should be noted that the current versions of GWLF do not make use of the improvements to USLE developed by the USDA-Agricultural Research Service for prediction of annual erosion, known as RUSLE (Renard et al., 1997). RUSLE provides corrections for the interaction of USLE parameters on a spatial and temporal scale that can improve sediment yield prediction; however, the USLE-based approach in GWLF has been found to perform well in a variety of watershed studies. The basic processes addressed in the GWLF simulation are shown schematically in Figure C-1. Actual implementation of the model makes use of the Windows-based version known as BasinSim (Dai and Wetzel, 1999). The GWLF application requires information on land use distribution, meteorology, and parameters that govern runoff, erosion, and nutrient load generation. In addition to the land use database, four primary data input classes are used to develop the model parameters for the watershed simulations: 1) soil and hydrologic properties, 2) nutrient concentration, buildup, and runoff assumptions, 3) onsite wastewater disposal information, and 4) meteorological data. The land use, watershed delineations, population, septic numbers, and meteorology data were collected and processed to generate a 10-year time series (April 1991 – March 2001 meteorology), which was used to derive seasonal and annual loading rates by land use type for each model HRU. C-3 Upper Rocky River Preliminary Findings Report February 2005 Precip itat ion ipita ion Ev apotranspiration potr nspir Erosion Ero (USLE) (USLE) Septic S ystem Loads ptic Loads Land Surface – SCS Curve Number Simulation Runoff Disso lv ed Nutr ients Nu nts Particu late ate Nut r ients Nut Loading to Loading to Stream Stre Unsaturated Zone Shallow Saturated Zone Ground wa ter oundw (Shallo w) (Sha Deep Seepage eepage Loss Loss Figure C-1. Schematic Representation of the GWLF Model Soil and Hydrologic Properties GWLF simulates rural soil erosion using the universal soil loss equation (USLE). This method has been applied extensively in North Carolina, so parameter values are well established. The physical variables used for the current study were adapted in large part from the calibrated GWLF model previously developed for the Falls Lake and Cane Creek watersheds (Cadmus, 1996). Runoff Curve Numbers: The direct runoff fraction of precipitation in GWLF is calculated using the curve number method from the NRCS TR55 method, based on imperviousness and soil hydrologic group. The soil hydrologic group was determined for subwatersheds using the STATSGO database. Weighted curve numbers were calculated for each land use category based on soil distribution among hydrologic groups A, B, C, and D (Table C-1). Forest CNs are assigned between the NRCS “Good” and “Fair” values, based on experience with the model in the Cane Creek and Falls Lake watersheds (Cadmus, 1995, 1996), while pasture was simulated as in “Fair” condition. C-4 Upper Rocky River Preliminary Findings Report Table C-1. February 2005 Curve Numbers for Antecedent Soil Moisture Condition II by Land Use and Soil Hydrologic Group Land Use Hydrologic Group A 44 47 50 53 56 68 80 89 49 49 67 33 45 77 98 Hydrologic Group B 64 66 67 69 72 79 87 92 69 69 78 57 66 86 98 Hydrologic Group C 76 77 78 80 81 86 91 94 79 79 85 71 77 91 98 Hydrologic Group D 82 83 84 84 85 89 93 95 84 84 89 78 83 94 98 Residential – Very Low Density Residential – Low Density Residential – Medium Low Density Residential – Medium High Density Residential – High Density Residential – Very High Density Office/Light Industrial Commercial/Heavy Industrial Urban Greenspace Pasture Row Crop Forest Wetlands Barren Water Evapotranspiration Cover Coefficients: The portion of rainfall returned to the atmosphere is determined by temperature and the amount of vegetative cover, which differs for each land use and varies by season (growing and dormant). For rural land uses, ET rates were based on seasonal values reported in the GWLF manual; for urban land uses, ET was calculated as 1 minus the impervious fraction. ET growing and ET dormant are the same for urban land uses whose pervious area is mostly lawn and landscaped plants. Barren land is assumed to have no significant plant cover, but water is still lost through evaporation. Soil Water Capacity: Water stored in soil may evaporate, be transpired by plants, or percolate to groundwater below the rooting zone. The amount of water that can be stored in soil and is available to evapotranspiration—the soil water capacity—varies by soil type and rooting depth. Average soil water capacity was estimated from STATSGO information on available water capacity in the soil column, assuming a rooted depth of 100 cm, yielding a value of 16.5 cm. Recession Coefficients: The rate of groundwater discharge to streams is governed by the recession coefficient. In theory, this coefficient can be determined by examining the flow hydrograph when gaging data are available. For use in the Jordan Lake watershed, a typical recession coefficient of 0.03 was used, based on previous GWLF applications to the Cane Creek and University Lake watersheds. Thus, a value of 0.03 was adopted for the Rocky River model. Deep Seepage Coefficient: The GWLF model has three subsurface zones: a shallow unsaturated zone, a shallow saturated zone (aquifer), and a deep aquifer zone. The deep seepage coefficient is the portion of the moisture content in the shallow saturated zone that seeps to the deep aquifer zone and does not C-5 Upper Rocky River Preliminary Findings Report February 2005 reappear as surface flow, effectively removing it from the watershed system. To model this process, the saturated zone is treated as a linear reservoir in which the moisture lost equals the moisture content multiplied by the saturation coefficient. Deep seepage is expected to be a small fraction in the watershed, as the Rocky River represents regional groundwater discharge axis, so that precipitation on the land surface eventually either returns to the atmosphere or flows to the Rocky River. However, some losses do occur due to withdrawal and consumptive use. A deep seepage coefficient of 1 percent appears to provide reasonable flow estimates on a watershed basis. Soil Erodibility (K Factor): Erosion in the GWLF model is simulated with the Universal Soil Loss Equation (USLE), for which four input factors are required (K, LS, C, and P). The first of these is the soil erodibility factor, K, which indicates the propensity of a given soil type to erode. Soil erodibility factors from the STATSGO database were analyzed by subwatershed. Weighted-average values by subwatershed vary from 0.23 to 0.33. Length-Slope (LS) Factor: Erosion potential varies by slope as well as soil type. The LS factor is the length (L) that runoff travels from the highest point in the watershed to the point of concentrated flow, multiplied by the slope (S), which represents the effect of slope steepness on erodibility for each soil type. LS factors for the Rocky River watershed were calculated using the Watershed Characterization System (Tetra Tech, 2000), which relies on topography and soils data (STATSGO) to calculate LS. LS factors in the Rocky River watershed ranged from 0.38 to 2.08 for the 50 subwatersheds. Cover and Management (C) and Practice (P) Factors: The mechanism by which soil is eroded from a land area and the amount of soil eroded depends on soil treatment resulting from a combination of land uses (e.g., forestry versus row-cropped agriculture) and the specific manner in which land uses are carried out (e.g., no-till agriculture versus non-contoured row cropping). Land use and management variations are represented by cover and management factors in the universal soil loss equation and in the erosion model of GWLF. Cover and management factors for non-agricultural land uses were drawn from several sources (Wischmeier and Smith, 1978; Haith et al., 1992; Novotny and Olem, 1994). Factors for agricultural land uses follow recommendations of the Orange County NRCS. The resulting factors are summarized in Table C-2. C and P factors are not required for the “urban” land uses, which are modeled in GWLF via a buildup-washoff formulation rather than with USLE. Table C-2. Cover and Management (C) and Practice (P) Factors for Land Uses in the Rocky River Watershed Land Use Residential – Very Low Density Barren Land Wetlands Forest Pasture Row Crop C 0.0065 0.5000 0.0030 0.0030 0.0110 0.1600 P 1.0000 1.0000 1.0000 1.0000 1.0000 0.5000 Sediment Delivery: Application of GWLF typically includes use of sediment delivery ratios that account for trapping of sediment and sediment-sorbed pollutants between the edge of field and the basin scale employed in the modeling. This empirical approach is a major source of uncertainty in GWLF modeling. Sediment delivery ratios were estimated based on catchment area using equations described in the Soil Conservation Service National Engineering Handbook, 1972 (Section 3, Chapter 6). C-6 Upper Rocky River Preliminary Findings Report February 2005 Nutrient Modeling Assumptions Soil Nutrient Concentrations: Soil nutrient concentrations were assigned based on their location within the Triassic Basin or the Carolina Slate Belt. In the Triassic Basin, the soil concentrations were initially set to 1,000 mg/kg for nitrogen and 616 mg/kg for phosphorus, based on results of calibrated GWLF model development for the Falls Lake study (Cadmus, 1995). In the Carolina Slate Belt, the soil concentrations were set to 600 mg/kg nitrogen and 475 mg/kg for phosphorus based on Carolina Slate Belt estimates used in the Jordon Lake Watershed Model (Tetra Tech, 2003). Groundwater Nutrient Concentrations: The GWLF model applies average groundwater nitrogen and phosphorus concentrations to flow from the saturated zone to the stream channel. For primarily rural agricultural watersheds, concentrations are based on the Cane Creek model (Cadmus, 1996) and assigned at 0.76 mg/L N and 0.07 mg/L P. Estimates for rural non-agricultural watersheds were adopted from the Falls Lake model results (Cadmus, 1995), and set at 0.25 mg/L N and 0.06 mg/L P. Falls Lake model estimates of 0.60 mg/L N and 0.10 mg/L P were also used for urban/developed areas. These values were initially developed from base flow nutrient concentrations observed in USGS studies of low-order streams. The groundwater component in GWLF, however, does not represent true groundwater flux alone. Because groundwater discharge varies slowly in comparison to overland runoff, the “groundwater” coefficient in a best-fit GWLF model includes true groundwater pathways and all components of nutrient load whose arrival at the watershed mouth is significantly delayed compared to the flow of water. Therefore, the calibrated groundwater concentrations are somewhat greater than would be expected in true baseflow discharge. Resulting estimates are shown in Table C-3. Table C-3. Groundwater Nutrient Concentrations by Land Use Parameter Rural Groundwater (agricultural areas) Rural Groundwater (non-agricultural areas) Urban Groundwater Septic Effluent Uptake Rate (g/day) Nitrogen (mg/L) 0.76 0.50 0.60 12.00 1.60 Phosphorus (mg/L) 0.07 0.06 0.10 1.50 0.40 Buildup Rates and Runoff Concentrations: In GWLF, nutrient loading from different land uses is based on the volume of flow and its pathways (overland or seepage), the amount of soil eroded, and coefficients that express the amount of nutrient load per unit volume of flow or erosion from a given land use. The GWLF model uses buildup/washoff relationships and runoff concentrations to predict nutrient loadings. These processes vary based on soil types and land use and are defined by a number of parameter values. Table C-4 presents values used in the Rocky River GWLF model. Runoff concentrations are based on those used in the Cane Creek and Falls Lake models, and are generally well established. Buildup and washoff rates from urban areas were set at values sufficient to reproduce annual stormwater unit loading rates developed for the Town of Cary (Tetra Tech, 2003a) when applied to Cary soil and hydrologic conditions. These loading rates were calculated from a modeling analysis of Event Mean Concentration (EMC) values (including Line et al., 2002; CH2M HILL, 2000; Greensboro, 2003; and U.S. EPA, 1983), and are in general agreement with export coefficients reported in the literature (CDM, 1989; Hartigan et al., 1983; U.S. EPA, 1983; Beaulac and Reckhow, 1982; Frink, 1991). EMC values associated with manure application were used for row crop and pasture land uses during the month of March when chicken manure is typically applied to agriculture areas. These EMC values were obtained from the GWLF manual (Haith et al., 1992). C-7 Upper Rocky River Preliminary Findings Report Table C-4. Nutrient Runoff and Buildup Rates Runoff and Buildup Rates Rural Land Uses Pasture Row Crop Pasture after manure application Row Crop after manure application Forest Wetlands Barren Residential – Very Low Density Urban Land Uses Residential – Low Density Residential – Medium Low Density Residential – Medium High Density Residential – High Density Residential – Very High Density Urban Land Uses Office/Light Industrial Commercial/Heavy Industrial Urban Greenspace Dissolved N (mg/L) 2.770 2.770 25.00 19.00 0.190 0.190 0.190 0.230 N Buildup (kg/ha/day) 0.171 0.193 0.234 0.174 0.160 N Buildup (kg/ha/day) 0.126 0.152 0.036 February 2005 Dissolved P (mg/L) 0.250 0.250 6.85 3.50 0.006 0.006 0.006 0.007 P Buildup (kg/ha/day) 0.032 0.032 0.032 0.030 0.026 P Buildup (kg/ha/day) 0.020 0.023 0.006 Onsite Wastewater Disposal The GWLF model simulates septic system nutrient contributions using nitrogen and phosphorus input values per capita and subtracting growing season plant uptake. Monthly nitrogen load contributed by normal septic tanks is assumed to mix with a larger reservoir of groundwater and enter the stream in proportion to local groundwater flow. For properly functioning systems, all phosphorus is assumed adsorbed by soils and retained. Septic systems that are either ponded or short-circuited are assumed to transfer phosphorus to the surface water with no losses to plant uptake and no adsorption attenuating the load. For this study, GWLF default values (Haith et al., 1992) are assigned for septic system nutrient contribution of 12 grams/capita/day of nitrogen and 1.5 grams/capita/day of phosphorus. The average rates of nutrient attenuation by plant uptake during the growing season were also set to default values of 1.6 g/day and 0.4 g/day for nitrogen and phosphorus, respectively. A steady-state failure rate of 2.5 percent was used to estimate the quantity of failed septic systems, based on the CDM (1989) study for the Little River Reservoir and Lake Michie subwatersheds, which assumes C-8 Upper Rocky River Preliminary Findings Report February 2005 a 10–15 percent steady-state rate of septic system failure, 20 percent of which is sufficiently close to waterbodies to cause direct loading. Loading rates for each low to medium-density residential land use (GWLF classes RVL, RLL, RML, and RMH) were estimated with and without onsite wastewater disposal for use in the nutrient loading model. Average lot size was used to determine the average number of houses per acre, and a population density of 2.5 people/household was assumed. The calculated loading rates were used in the subsequent watershed scale analysis that took into account areas assumed to be sewered versus areas assumed to use onsite treatment. Weather Data The GWLF model hydrologic simulation is driven by daily precipitation totals and maximum and minimum daily temperature. Potential evapotranspiration is calculated from temperature. The meteorological data required by GWLF was collected and processed for the meteorological stations at Siler City, NC. The raw data was obtained from the Southeast Regional Climate Center and the National Climatic Data Center for 1990 through 2001. Unit Area Nonpoint Loads As discussed in the previous section, GWLF is used to generate unit loading rates for the Rocky River watershed land uses within 50 subwatersheds in the study area. Complete results (seasonal and annual) are provided in Appendix A. Average loading rates by land use are summarized in Table C-5. Table C-5. Summary of Average Annual Field-Scale Loading Rates by Land Use Across All HRUs (lb/ac/yr) Land Use Description Barren Forest Pasture Row Crop Water Wetland Commercial/Office Residential <0.25 ac per unit Residential - 0.25-0.5 ac per unit Residential - 0.5-1.0 ac per unit Residential - 1.0-1.5 ac per unit Residential - 1.5-2 ac per unit Residential - 2+ ac per unit TN 13.55 0.12 3.29 6.54 0.0 0.16 14.76 8.85 6.31 6.22 6.90 4.27 4.44 TP 10.45 0.05 0.74 2.07 0.0 0.06 2.28 1.45 1.07 1.03 1.14 0.80 0.73 Code BAR FOR PAS ROW WAT WET COM RVH RHH RMH RML RLL RVL The field-scale loading rates generated by the GWLF application tend to be comparable to those reported in the literature for similar land uses (Table C-6). C-9 Upper Rocky River Preliminary Findings Report Table C-6. GWLF Land Use RVL, RLL RMH, RHH RVH COM ROW PAST FOR Notes: 1 February 2005 Comparison of GWLF Field-Scale Loading Rates to Literature Export Coefficients GWLF Field-Scale Total P Loading (lb/ac/yr) 0.73 - 0.80 1.03 - 1.07 1.45 2.28 2.07 0.74 0.05 Literature Total P Export Coefficients (lb/ac/yr) 0.25 – 0.91 0.86 – 1.112 1.6 – 1.81 1.6 – 3.412,3 0.60 - 2.40 0.44 - 2.18 0.04 – 0.121 2,4,5 GWLF Field-Scale Total N Loading (lb/ac/yr) 4.27 - 4.44 6.22 – 6.90 8.85 14.76 6.54 3.29 0.12 Literature Total N Export Coefficients (lb/ac/yr) 3.0 – 6.51 6.0 – 8.812 11.7 – 13.31 10.7 – 25.012,3 4.0 - 50.0 2.0 - 5.5 0.6 – 2.812,4,5 CDM (1989); 2Hartigan et al. (1983) (surface only); 3US EPA (1983); 4Beaulac and Reckhow (1982); 5Frink (1991). C-10 Upper Rocky River Preliminary Findings Report February 2005 Appendix D. Summary of Existing Water Quality Data D-1 Upper Rocky River Preliminary Findings Report February 2005 (This page left intentionally blank.) D-2 February 2004 North Carolina Division of Water Quality Water Quality Section Revised February 5, 2004 Summary of Existing Water Quality Data Rocky River Watershed, Chatham County Cape Fear River Basin Subbasin 03-06-12 Catalog Unit # 03030003 HU # 070010, 070020, 070050 This document provides a summary of the existing water quality data for the portion of the Rocky River watershed represented by the three hydrologic units listed above. The intent of this summary is to provide a synopsis of existing information to support the watershed characterization (Phase 1) portion of the Local Watershed Planning process initiated in this area by the North Carolina Ecosystem Enhancement Program. I. Background A. Location • Rocky River is a major tributary of the Deep River, approximately 35 river miles in length. Multiple tributaries drain into Rocky River within the study area, including Loves Creek, Tick Creek, and Bear Creek. • The study area is located in Chatham County, except for portions of the Rocky River headwaters located in Alamance and Randolph counties. • The Town of Siler City lies entirely within the watershed and is drained by several unnamed tributaries that form a confluence just south of the city into Loves Creek. B. Stream Classifications Stream Classifications within the watershed are shown in Table D-1. D-3 February 2004 Table D-1. Stream Stream Classifications for Rocky River Watershed Index # 17-43-7.5 17-43-8a 17-43-8b 17-43-8c Description From source to .3 mile downstream of Lacy Creek From dam at lower water supply to US 64 From US 64 to SR 2170 From SR 2170 to NC 902 From source to above WWTP near SR 2203 From below WWTP near SR 2203 to Rocky River Source to Rocky River, NC 421, Chatham Co. From source to SR 2189, Chatham Co. From SR 2189 Chatham Co, to Rocky River From SR 2333 Chatham Co, to Rocky River From SR 2155 Chatham Co, to Rocky River Classification WS III C C C C C C C C C C Rocky River 17-43-1 From .3 mile downstream of Lacy Cr to dam below Siler City WS III CA Loves Creek 17-43-10a 17-43-10b Tick Creek Bear Creek 17-43-13 17-43-16a 17-43-16b 17-43-16c 17-43-16d WS III = water supply, CA = critical area, C = aquatic life & secondary recreation, freshwater. WWTP = wastewater treatment plant. Adapted from Cape Fear River Basin Schedule of Classifications (http://h2o.enr.state.nc.us/bims/Reports/reportsWB.html) C. Overview of Data Availability Data sources for the three Rocky River hydrologic units include (Figure D-1): • Benthic macroinvertebrate community monitoring at two sites on the Rocky River, two sites on Loves Creek, two sites on Tick Creek, and three sites on Bear Creek. • Aquatic and Riparian Habitat assessments for benthos and fish sites sampled in 2002 and 2003. • Fish Community Assessment (NCIBI) from one site in Rocky River, Loves Creek, Tick Creek, and Bear Creek. • Ambient chemistry data conducted by the Upper Cape Fear River Basin Association (UCFRBA) at two monitoring stations on the Rocky River near US 64 (B5980000), and near SR 2170 (Rives Chapel Ch Rd) (B5950000). The Division of Water Quality (DWQ) operates ambient station B6000000 at NC 902 near Pittsboro, but this station is not located within the study area. • Fish tissue data from the Rocky River near SR 1300 (Staley Snow Camp Rd) from May 1998. • Lake assessment data for the Rocky River Reservoir monitored by DWQ in June, July, and August, 1998 and 2003. D. Wastewater Discharges Discharges include several Chatham County schools and a rest home, which discharge less than 1 MGD (million gallons per day) in the Bear Creek drainage. The only major permitted wastewater discharge in the study area is the Siler City WWTP, permitted to 4.0 MGD to Loves Creek (Permit # NC0026441). E. Impaired Waterbodies The 303(d) list classifies the Rocky River as impaired from its source to the Rocky River Reservoir. Habitat degradation is listed as a potential cause of impairment. Loves Creek is considered to be D-4 February 2004 biologically impaired for its entire length. Urban runoff and the WWTP discharge are listed as potential sources (NCDWQ, 2003a). â UCFRBA Stations Fish Stations ð Ambient Stations R oc # ³ Ú Macroinvertebrate Stations NPDES ky # R iv Lo ve sC re ek ³ # â ³ ³ # #Ú er US 64 Ú Ê Hydrologic Unit 0010 0020 0050 NC 902 ³ # ³ # ³ # SR 2158 ³ # ³ SR 2170 # â ³ eek # Tick Cr SR 2120 US 421 # ³ ð SR 2189 Ú ³ # SR 2155 Bear Creek Ú Ú ³ # ³ # US 15/501 ³ # SR 2333 Figure D-1. Hydrologic Units in the Rocky River Watershed of Chatham County, North Carolina II. Summary of Existing Data A. Benthic Macroinvertebrate Data Benthic macroinvertebrate samples have been collected from two mainstem Rocky River locations, and three tributaries, including special studies of the Siler City WWTP in 1997 and 1989. Data are summarized in Table D-2. D-5 February 2004 Table D-2. Bioclassification Data for the Rocky River Study Area Site, Location Rocky River, SR 2170 Date 7/22/2003 9/30/2002 7/9/1998 6/27/1997 7/27/1993 8/2/1989 7/21/2003 7/9/1998 6/27/1997 7/27/1993 8/1/1989 6/24/2003 6/27/1997 8/1/1989 6/24/2003 6/27/1997 8/1/1989 6/22/2003 6/23/2003 6/24/2003 6/25/2003 Feb-98 Jul-93 Aug-85 Jul-03 Jul-98 Aug-91 Aug-91 Mar-03 Jul-90 EPT 15 8 18 19 19 11 15 17 20 12 16 7 8 7 6 4 2 13 7 3 4 18 5 19 20 15 16 15 16 15 BI 5.87 4.87 6.28 6.48 6.54 6.74 6.51 6.42 6.74 6.94 6.73 7.37 7.25 7.5 6.72 7.41 8.41 6.31 7.14 7.63 7.32 4.86 6.57 6.54 6.46 5.93 6.78 6.51 5.05 4.86 EPTBI Bioclassification 4.99 4.87 5.07 5.60 5.38 6.13 5.44 4.63 5.72 5.68 5.81 6.95 6.61 6.85 7.04 6.06 6.62 4.34 6.42 7.10 6.43 4.81 6.57 5.41 5.93 5.93 5.80 5.58 5.05 4.86 Good-Fair Fair Good-Fair Good-Fair Good-Fair Fair Fair Good-Fair Good-Fair Fair Fair Fair Fair Fair Fair Poor Poor Not Rated Fair Not Rated Not Rated Good-Fair Poor Good-Fair Good-Fair Good-Fair Not Rated Not Rated Not Rated Not Rated Habitat 78 84 Rocky River, US 64 76 Loves Creek, above WWTP near SR 2203 55 Loves Creek, below WWTP near SR 2203 78 Loves Creek, below Golf Course Loves Creek, 2nd Avenue Loves Creek, SR 1006 UT Loves Creek, Greensboro Rd Tick Creek, US 421 63 64 70 55 Tick Creek, SR 2120 Bear Creek, SR 2333 Bear Creek, SR 2189 Bear Creek, SR 2155 69 85 EPT = Taxa richness of mayfly, stonefly, and caddisfly species. BI = Biotic index. Adapted from NCDWQ 1999, 2003b. *EPTBI = Biotic index for EPT species. UT = unnamed tributary. Not Rated = Bioclassification not assigned due to low flow conditions and/or low stream width. Synopsis of Benthic Data Rocky River. The upstream station at US 64 was Fair in 2003, though it was rated Good-Fair in several previous years. The benthic community at the downstream location, SR 2170, was Good-Fair in 2003 and in most samples since 1993. Both sites were rated Fair when first sampled in 1989. Loves Creek. Special surveys on Loves Creek have been conducted to assess the effects of the Siler City WWTP discharge. The benthic community was rated Poor below the discharge in 1989 and 1997, while the site obtained a Fair rating in 2003. Changes in the benthic community suggest some improvement in water quality in 1997 and 2003. Loves Creek above the discharge is also a highly degraded stream, receiving a Fair rating in 2003 and in previous years. D-6 February 2004 Tick Creek. Two stations on this stream have generally been rated Good-Fair. Bear Creek. Benthic community samples collected in Bear Creek have not been rated. However, the number of EPT taxa collected have been consistently higher than EPT taxa richness in Loves Creek, and BI values have been lower, indicating a more intact benthic fauna. B. Aquatic and Riparian Habitat During the basinwide assessments of benthic communities, stream habitat and riparian area conditions were evaluated for each sampling site (NCDWQ, 2003b). This protocol rates the aquatic habitat of the sampled reach by adding the scores of a suite of local habitat factors (reach scale) relevant to macroinvertebrates and fish. Total scores range from worst (0) to best (100). Individual factors include (maximum factor score in parentheses): • • • • • • • • Channel modification (5) In-stream habitat variety and area available for colonization (20) Bottom substrate type and embeddedness (15) Pool variety and frequency (10) Riffle frequency and size (16) Bank stability and vegetation (14) Light penetration/canopy coverage (10) Riparian zone width and integrity (10) Overall habitat was adequate at Rocky River and Bear Creek sites with scores ranging from 76 to 85 out of 100 (Table C-2). Habitat in Loves Creek was more degraded, especially upstream (score of 55). Habitat in the Rocky River is typical of slate belt streams with infrequent boulder/rubble riffles. Productive snags and undercut bank habitat were evident at the US 64 site. Tick Creek at SR 2120 is about 4 meters wide and has infrequent boulder riffles. Bank erosion is severe along this reach and cattle have direct access to the stream. The land use at this location is mostly forested and pasture. C. Stream Fish Community Assessment (NCIBI) The North Carolina Index of Biological Integrity (NCIBI) was initiated in the early 1990s to assess a stream’s biological integrity through examination of fish community structure and health (NCDWQ, 2001). The scores for 10 metrics (including species richness and composition, indicator species, trophic function, abundance, condition, and trophic function) are summed to obtain an overall NCIBI score, which determines the bioclassification. Data are summarized in Table D-3. D-7 February 2004 Table D-3. NCIBI, Rocky River Watershed, Chatham County Station, Location Bear Creek, SR 2187 Date 06/13/03 10/29/99 04/07/99 04/23/98 Loves Creek, SR 2229 05/05/03 05/04/98 Rocky River, SR 1300 5/5/2003 05/04/98 Tick Creek, US 421 06/13/03 04/19/94 NCIBI Score 44 36 40 50 44 52 40 44 38 56 NCIBI Rating Good-Fair Fair Good-Fair Good Good-Fair Good Good-Fair Good-Fair Fair Excellent NCIBI = North Carolina Index of Biological Integrity. Adapted from NCDWQ 1999. NOTE: some metric constructs have changed and sites have been re-rated since the Cape Fear Assessment Report (NCDWQ 1999) was written. Ratings for some sites in that document have been modified. Bear Creek, SR 2187 (Meronies Church Rd) watershed drains a portion of the southwest corner of Chatham County and is subject to considerable flow variability during the summer. These variable flows are believed to be the primary reason for the NCIBI rating variations. Loves Creek, SR 2229 (above Siler City’s WWTP) drains much of Siler City south of US 64. The species diversity and fish abundance metrics in 1998 scored high and the number of species of sunfish collected indicated good instream pool habitat. Tick Creek was found to decline in fish diversity from Excellent to Fair. Although habitat degradation has been observed where cattle have access to the stream, the reason for the decline is not clear, and the site will be resampled. A fish sample from above the Rocky River Reservoir was given a Good-Fair NCIBI score in 2003 and 1998, possibly reflecting the effects of nonpoint source runoff and enrichment. Forty-four percent of the fish collected in 1998 were the tolerant redbreast sunfish. Note that this site was originally rated Fair in 1998 (NCDWQ, 1999), which resulted in the classification of this portion of the Rocky River as impaired. This sample has since been re-rated. D. Ambient Chemistry Data UCFRBA conducted ambient chemistry data at two monitoring stations on the Rocky River. The site near US 64 (B5980000) is located above the confluence with Loves Creek, which receives the discharge from the Siler City WWTP. The site near SR 2170 (B5950000) is located below the Loves Creek confluence. Conductivity, total phosphorus and nitrate levels were substantially higher at the downstream site, likely reflecting the effect of the discharge. Dissolved oxygen levels were generally adequate at both sites, with concentration between 4 and 5 mg/L occasionally observed. D-8 February 2004 Table D-4. Ambient Data for Rocky River Upstream (B59500000) and Downstream (B59600000) of the Siler City WWTP: April 2000 – August 2003* UPSTREAM DOWNSTREAM EVALUATION LEVEL % < or > EL (N) TEMP (oC) DO (mg/L) pH Conductivity (umhos/cm) Turbidity (NTU) TSS (mg/L) Fecal Coliform (no/100ml) NH3 (mg/L) NO2+NO3 (mg/L) TKN (mg/L) TP (mg/L) Al (ug/L) Cu (ug/L) Fe (ug/L) Mn (ug/L) Zn (ug/L) 62 62 62 62 41 41 41 10 10 10 10 8 8 8 5 8 min 4.4 4.0 5.8 50 <0.50 <1.0 4.0 0.0 0.3 0.4 0.1 190 3.2 860 88 10 mean 19.8 7.7 7.0 106.5 12.0 6.4 84.7 0.1 1.6 0.7 0.2 601 4.6 1513.3 129.2 37.8 1 max 29.8 13.6 8.3 172 110 62 12000 0.1 4.7 1.2 0.3 1700 6.1 3000 230 260 (N) 62 61 62 62 min 4.0 4.4 5.6 56 mean 18.9 7.4 7.2 415.5 10.8 7.5 143.41 0.1 6.9 1.0 0.4 345 5.9 861 54.6 25.4 max 27.0 13.0 8.7 1072 120 75.6 6800 0.6 23.8 1.7 2.5 1600 18 2900 95 220 EL >32 <5 6-8 ->50 >10 >2001 ->10 ->0.05 ->7 >1000 >200 >50 US 0 8.1 3.23 -2.4 9.8 --0 -100 -0 87.5 20 12.5 DS 0 4.9 3.23 -2.4 9.8 --24.4 -100 -31.8 31.8 0 4.5 41 <0.40 41 41 42 41 43 48 22 22 22 10 22 1.0 7.0 0.0 0.1 0.2 0.1 60 2.1 <50 37.0 10.0 *Evaluation Level (EL) = presented to facilitate review. Measurements should not exceed the range (< or >) indicated by EL. Ranges adapted from NCDWQ April 2003. US = upstream, DS = downstream. Nickel, Mercury, Arsenic, Cadmium, Chromium, and Lead all below the quantitation limit for all samples analyzed. 1 Geometric mean. E. Discharge Compliance Data The Siler City WWTP (Permit # NC0026441) discharges effluent into Loves Creek. The plant conducts quarterly effluent toxicity tests (chronic tests with an instream waste concentration of 96 percent). A review of test results from 1999 to 2000 indicated no test failures. A review of compliance data indicates violation of effluent standards for BOD, ammonia, pH, and mercury during 2003. Civil penalties were assessed for some of these violations. F. Fish Tissue Data Fish tissue samples were collected from the Rocky River at SR 1300 during May 1998. Nine samples were analyzed for metals contaminants. All concentrations were below EPA and FDA/NC limits (see NCDWQ 1999 for details). D-9 February 2004 G. Lake Assessment Program Rocky River Reservoir serves as a water supply for the Town of Siler City. Public access to the lake is restricted. The impoundment was enlarged in 1988 to raise the existing storage capacity from 60 million gallons to 424 million gallons, raising the water level by approximately 10 feet. The watershed is primarily agricultural with some pasture immediately adjacent to the lake. The lake was last sampled by DWQ during the summer of 2003 (Table D-5), when it was considered Hypereutrophic. ROCKY RIVER RESERVOIR th or N g on Pr CPF1201B N 1 SR 362 CPF1201A Rock y In the past, elevated levels of iron and manganese in the raw water resulted in taste and odor complaints (the water plant now treats the raw water for elevated manganese). The water treatment plant samples the lake at the intake for various water quality parameters including pH, iron, manganese, turbidity and alkalinity. Fecal coliform bacteria sampling is conducted monthly and sampling for inorganics and organics are sampled annually. Turbidity and low dissolved oxygen in Rocky River Reservoir have been observed after rainfall events. These problems are usually temporary (NCDWQ, 1999). 0 1/2 mile Rive r Table D-5. Date 8/12/03 7/9/03 6/12/03 08/06/98 07/08/98 06/03/98 07/29/93 08/01/91 Rocky River Reservoir NCTSI Data NCTSI 6.0[H] 5.5[H] 5.7[H] no score 3.9[E] 4.1[E] 5.4[H] 4.1[E] TP (mg/L) 0.17 0.16 0.19 0.08 0.07 0.18 0.10 0.10 TON (mg/L) 1.19 1.14 1.06 0.66 0.51 0.46 0.92 0.55 CHLA (ug/L) 30 28 37 n/a 35 15 38 41 SECCHI (m) 0.5 0.7 0.7 0.5 0.4 0.5 0.4 0.7 NCTSI = North Carolina Trophic State Index. [E] = Eutrophic, [H] = Hypereutrophic. Adapted from NCDWQ 1999. H. Other Issues Several freshwater mussel species which are proposed for state protection (Alasmidonta undulata, A. varicosa and Strophitus undulatus) have been collected from the Rocky River (NCDWQ, 1999). D-10 February 2004 III. Conclusions • Benthic and fish communities in the Rocky River have generally been meeting their uses in recent years, but some impacts are evident. Ratings have generally been Good-Fair over the past decade, with occasional Fair benthic community ratings. The impact of the Siler City WWTP discharge on the portion of the Rocky River downstream of the Loves Creek confluence is evident from ambient monitoring data, though significant effects on benthic communities in the Rocky River mainstem have not been evident in recent years. • While the portion of the Rocky River above the reservoir is currently classified as impaired, this classification is likely to change. Fish community sampling in 2003 indicated a Good-Fair community, and the 1999 collection has been re-rated from Fair to Good-Fair. • Loves Creek is impaired both above and below the Siler City WWTP due to highly impacted benthic communities. The stream is likely degraded by urban runoff impacts in addition to wastewater effects. The fish community was rated Good-Fair in 2003, however. • The benthic community of Tick Creek indicates some water quality degradation, though the stream has generally been meeting its uses (predominately Good-Fair ratings). However the fish community declined from Excellent in 1994 to Fair in 2003. The reason for the decline is not apparent. • The benthic community in Bear Creek has not been rated. The fish community was Good-Fair in 2003, but has fluctuated in the past, most likely reflecting the effects of flow variability in this slate belt stream. • Nutrient levels in the Rocky River Reservoir are elevated, and the lake was considered to be hypereutrophic based on sampling during the summer of 2003. IV. References Cited NCDWQ 1999. Basinwide Assessment Report for the Cape Fear River Basin. Environmental Sciences Branch. June. NCDWQ 2001. Standard Operating Procedures. Stream Fish Community Assessment and Fish Tissue. March. NCDWQ 2003. Classifications and Water Quality Standards Applicable to Surface Waters and Wetlands of NC. NCDENR. Division of Water Quality. April. NCDWQ 2003a. North Carolina Water Quality Assessment and Impaired Waters List [2002 Integrated 305(b) and 303(d) Report]. Planning Branch. February. NCDWQ 2003b. Standard Operating Procedures for Benthic Macroinvertebrates. Biological Assessment Unit. July. D-11 February 2004 (This page left intentionally blank.) D-12 February 2005 Appendix E. Water Quality Monitoring Plan E-1 February 2005 (This page left intentionally blank.) E-2 February 2005 North Carolina Division of Water Quality Water Quality Section Water Quality Monitoring Plan Rocky River Watershed, Chatham County Cape Fear River Basin Subbasin 03-06-12 Catalog Unit # 03030003 HU # 070010 (54 sq. mi.) # 070020 (71 sq. mi.) # 070050 (52 sq. mi.) This document presents a strategy for chemical, physical and biological water quality monitoring for the portion of the Rocky River watershed represented by the three hydrological units listed above, whose total drainage area is 177 square miles. The purpose of this plan is to recommend additional water quality monitoring as part of the preliminary findings (Phase 1) portion of the Local Watershed Planning process initiated in this area by the North Carolina Ecosystem Enhancement Program (EEP). The proposed monitoring will be carried out by DWQ during Phase 2. I. Background A summary of existing water quality data was presented in a separate document to support the watershed characterization (Phase 1) portion of the planning process (NCDWQ, 2004a). It provided a partial framework for this plan and a condensed version of the summary is provided below. Existing data indicate that Loves Creek is impaired, both upstream and downstream of the Siler City WWTP discharge point (NCDWQ, 2004b). The Rocky River and its tributaries Tick Creek and Bear Creek have somewhat better biological communities (fish and benthic invertebrates) than Loves Creek, and are not considered impaired. A portion of the Rocky River above Rocky River Reservoir is listed as impaired (NCDWQ 2004b) but this reach is likely to be removed from the 303(d) list, based on recent monitoring. Loves Creek has generally degraded habitat compared to the other streams in the study area. Both point source wastewater and nonpoint (storm water) sources appear to be contributing to impairment, while the recent drought may have exacerbated the situation in these slate belt streams. Nutrient levels in the Rocky River Reservoir are elevated, and the lake was considered to be hypereutrophic based on sampling during the summer of 2003. E-3 February 2005 II. Water Quality Monitoring Goals A. Characterize baseline water quality conditions for selected streams where no water quality data exists. Due to resource limitations it is not feasible to characterize water quality in all streams within the planning area. However, selected high priority areas can be monitored. B. Assess water quality impacts due to upstream subwatershed activities. Additional monitoring is warranted in areas where water quality impacts have been documented or are suspected. For example, the eutrophic condition of Rocky River Reservoir warrants investigation of the sources of nutrient input to this lake and Lower Rocky River Reservoir, which is the drinking water source for Siler City. Upper Rocky River, North Prong Rocky River, Greenbrier Creek and Mud Lick Creek are the primary tributaries to these lakes. C. Evaluate Loves Creek impairment issues. The impairment of Loves Creek is already being evaluated by DWQ, and biological sampling was done at six locations in June 2003 as part of a Total Maximum Daily Load (TMDL) Stressor Study. Additional chemical monitoring is recommended for Phase 2 of the EEP local watershed plan. III. Monitoring Approach Biological Assessment Biological assessment involves the collection and identification of stream organisms to determine and evaluate community structure and diversity that result from water quality and habitat conditions. Biological assessment also involves the evaluation of habitat conditions, which is an essential part of the assessment process. Stream organisms and habitat provide clues with respect to watershed condition and functioning. Benthic data collected to date (see NCDWQ 2004a) are adequate to characterize the Loves Creek watershed, most of Rocky River and the Tick Creek and Bear Creek watersheds. Additional benthic surveys/sampling and evaluation of aquatic habitat conditions, at other streams for which benthic surveys do not exist, would be desirable but are not proposed (Table 1) due to workforce limitations. Fish data already collected seem adequate, and no additional fish sampling is proposed. Chemical/Physical Assessment Chemical/physical assessment involves sampling and measuring various chemical and physical parameters to characterize existing conditions. It can also identify the nature and sources of stressors to benthic and fish communities. These data are compared to other watersheds within the planning area and against established water quality standards, criteria and benchmarks to provide clues with respect to watershed condition and functioning. Existing chemical data are limited. The Upper Cape Fear River Basin Association (UCFRBA) samples locations on the Rocky River at two locations within the study area, including one location upstream, and one downstream of the Loves Creek confluence. DWQ also samples the Rocky River further downstream at NC 902 (outside of the study area), as part of the monthly ambient monitoring program. These sampling programs by DWQ and UCFRBA will continue on a monthly basis, as shown in Table 1. E-4 February 2005 Chemical monitoring is recommended for Loves Creek upstream of the Siler City WWTP to investigate nonpoint source impacts in this impaired stream. A location downstream of the WWTP will also be sampled to evaluate the nutrient input of this stream to the Rocky River. Synoptic monitoring is also proposed for a number of streams for which no chemical monitoring data are currently available. These include: North Prong Rocky River, Greenbrier Creek, Mudlick Creek, Varnell Creek, Bear Creek, and Tick Creek (Table 1). Type and Frequency of Sampling Eleven sites indicated in Table 1 and Figure 1 (large black dot) will be sampled during baseflow conditions, which is defined as a period of at least 48 hours without rainfall. Storm samples will be collected, if feasible, at the six sites indicated in Table 1; however, logistical constraints and the nature of many storm events make it infeasible to collect storm samples at all sites during any particular storm. Additional storm sampling at the other locations on Table 1 may also done as opportunities arise; priority will be given to those sites that have not been sampled previously. The goal of storm sampling is to collect samples during the rising stage of the storm hydrograph. Storm samples will normally be collected manually. Automatic sampling equipment may also be used at the sites with USGS gaging stations, where it might provide additional information on pollutant transport rates. Baseflow samples will be collected on a monthly basis from September 2004 to March 2005. Three storm samples will be collected, representing summer, fall and winter. Selected Parameters Field parameters (dissolved oxygen, specific conductance, pH, and water temperature) will be measured at all stations. Samples will be collected for laboratory analysis of nutrients (total phosphorus, ammonia, TKN and nitrite-nitrate), suspended residue, turbidity, metals, and fecal coliform. Table 2 contains a complete parameter listing. Toxicity testing is planned for Loves Creek due to is impaired status. At other locations, toxicity testing and other parameters (i.e., BOD, pesticides) may be evaluated if conditions warrant and if resources allow. Methods Water temperature, dissolved oxygen, pH and specific conductance will be measured in situ using appropriate field instrumentation. Samples for other parameters will be submitted to the DWQ Laboratory Section for analysis. Chemical and physical monitoring will be conducted according to the procedures described in the Intensive Survey Unit’s Standard Operating Procedures (SOP) manual (NCDWQ, 2003b) and the DWQ Laboratory Section’s sample submission guidance (NCDWQ, 2002). Analytical methods used by the DWQ Laboratory Section for the parameters covered by this monitoring plan are listed in Table 2. Biological monitoring (benthic communities and habitat) will be conducted according to procedures described in the Biological Assessment Unit’s (BAU) SOP (NCDWQ, 2003c). E-5 February 2005 Table E-1. Proposed Chemical/Physical/Biological Monitoring Locations and Descriptions for Rocky River (CPF) Local Watershed Plan. See notes at bottom of table. Upstream Landuse Drainage Area (sq. miles) Chemical/ Physical1 BF SF Benthos(B) Fish (F) 1 Site Code Monitoring Location CPF12_A001 Rocky River at SR 1300 (USGS Gage) Mostly agriculture plus urban. 7.4 X X F CPF12_A002 N. Pr. Rocky R SR 1300 Mostly agriculture Mostly agriculture Mostly agriculture Ag plus urban, commercial, residential. Urban, commercial, residential Urban, commercial, residential. Agriculture plus forest. All land uses. Ag, plus suburban, residential. Ag plus urban, commercial, residential. Mostly forest with ag. Agriculture plus forest Agriculture plus forest. approx. 9 X X CPF12_A003 CPF12_A004 Greenbrier Cr SR 1346 Mud Lick Cr SR 1355 Rocky River at US 64 (B5980000 UCFRBA) Loves Creek above WWTP near SR 2203 Loves Creek below WWTP Varnell Cr at SR 1503 Rocky River at SR 2170 (B5950000 UCFRBA) approx. 7 approx. 11 X X CPF12_A005 approx. 65 X B CPF12_A006 approx. 7.5 X X BF CPF12_A007 CPF12_A008 approx. 7.5 approx. 8 X X B CPF12_A009 approx. 90 X B CPF12_A010 Tick Cr at US 421 (USGS Gage) Rocky River at NC 902 (B6000000 NCDWQ) Bear Creek at SR 1141 Bear Creek at SR 2333 Bear Creek at SR 2155 15.5 X X BF CPF12_A011 approx. 140 X CPF12_A012 CPF12_A013 CPF12_A014 1 approx. 13 approx. 25 approx. 50 X X X X X B BF Notes: X or B in an unshaded box indicates proposed monitoring to be undertaken as part of this assessment. Shaded boxes indicate data collections that are already completed or ongoing, but not part of this assessment. E-6 February 2005 Table E-2. DWQ Laboratory Section -- Methods and Practical Quantitation Limits (PQL) EPA Method 1 Parameter APHA Method 2 Other Method PQL Revision Date 3/13/01 3/13/01 3/13/01 7/24/01 7/24/01 7/24/01 7/24/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 3/13/01 Coliform, MF fecal Susp. residue Turbidity NH3 as N TKN as N NO2+ NO3 as N P total as P Cadmium (Cd) Chromium (Cr) Copper (Cu) Nickel (Ni) Lead (Pb) Zinc (Zn) Aluminum (Al) Calcium (Ca) Iron (Fe) Magnesium (Mg) Arsenic (As) 1 2 600/8-78-017 160.2 180.1 350.1 and 350.2 350.1 and 351.2 353.2 365.1 200.8/213.2 200.8/200.7 200.8/220.2 200.8/200.7 200.8/239.2 200.8/200.7 200.7 200.7 200.7 200.7 200.8/206.2 9222D 2540D 2130B 1 colony/100mL 2 mg/L 1 NTU QUIK CHEM 10-107- 0.01 mg/L 06-1-J QUIK CHEM 10-107- 0.20 mg/L 06-2-H QUIK CHEM 10-107- 0.01 mg/L 04-1-C QUIK CHEM 10-115- 0.02 mg/L 01-1-EF 2.0 µg/L 25 µg/L 2.0 µg/L 10 µg/L 10 µg/L 10 µg/L 50 µg/L 0.10 mg/L 50 µg/L 0.10 mg/L 10 µg/L Information on EPA methods available at http://www.esb.enr.state.nc.us/lab/qa/epamethods/epamethods.htm APHA reference: Standard Methods for the Examination of Water and Wastewater, 18th ed. E-7 February 2005 E-8 February 2005 References NCDWQ. 2002. Guidance for Sample Submission. NCDWQ Laboratory Section. April. Available online at http://www.esb.enr.state.nc.us/lab/qa.html. Current sample preservation requirements are available on-line at http://www.esb.enr.state.nc.us/lab/qa/collpreswq.htm. NCDWQ. 2003b. Intensive Survey Unit Standard Operating Procedures. Environmental Sciences Branch. August. Available on-line at http://www.esb.enr.state.nc.us/isu.html NCDWQ. 2003c. Standard Operating Procedures for Benthic Macroinvertebrates. Biological Assessment Unit. Environmental Sciences Branch. July. Available on-line at http://www.esb.enr.state.nc.us/BAU.htm] NCDWQ. 2004a. Summary of Existing Water Quality Data, Rocky River Watershed, Chatham County. Water Quality Section. February. NCDWQ. 2004b. North Carolina Water Quality Assessment and Impaired Waters List (2004 Integrated 305(b) and 303(d) Report. Public review draft. April. E-9 February 2005 (This page left intentionally blank.) E-10 Upper Rocky River Preliminary Findings Report February 2005 Appendix F. Modeling Results and Rankings F-1 Upper Rocky River Preliminary Findings Report February 2005 (This page left intentionally blank.) F-2 Upper Rocky River Preliminary Findings Report Table F-1. Modeling Results and Rankings Subwatershed Phosphorous Loading Number (lb/acre/yr) BC13 MR13 MR16 BC04 BC01 MR18 BC02 MR22 BC14 BC05 BC12 MR19 MR15 BC10 BC07 BC09 MR12 UR04 BC03 MR06 MR17 MR09 MR05 BC11 MR14 BC08 UR05 BC06 UR03 UR10 MR11 UR13 MR02 UR08 MR01 MR21 UR09 MR20 UR02 MR03 MR10 UR14 UR11 UR07 MR04 UR06 MR08 UR01 UR12 MR07 QUARTILE RESULTS Minimum 1st Quartile Median Value 3rd Quartile Maximum 0.04 0.13 0.26 0.43 0.78 Minimum 1st Quartile Median Value 3rd Quartile Maximum 0.38 0.64 0.74 0.91 1.44 0.38 0.47 0.48 0.53 0.54 0.55 0.56 0.56 0.58 0.58 0.60 0.60 0.62 0.64 0.65 0.65 0.67 0.68 0.68 0.68 0.70 0.71 0.71 0.71 0.73 0.74 0.75 0.76 0.80 0.80 0.82 0.82 0.85 0.87 0.89 0.89 0.89 0.90 0.93 0.93 0.96 1.03 1.04 1.08 1.09 1.10 1.15 1.15 1.17 1.44 February 2005 Subwatershed Overland Sediment Loading Number (ton/acre/yr) BC02 BC07 BC04 BC01 BC03 BC09 BC13 MR07 BC05 BC12 BC11 BC06 BC14 BC08 BC10 UR04 MR08 MR13 MR16 MR18 MR06 MR22 MR04 MR19 MR12 MR17 MR15 MR09 MR05 MR14 UR05 UR06 UR03 UR02 UR10 UR08 MR11 UR01 MR20 MR02 UR13 UR09 MR01 MR21 MR03 MR10 UR07 UR11 UR14 UR12 0.04 0.04 0.04 0.05 0.05 0.05 0.05 0.07 0.08 0.08 0.11 0.11 0.13 0.13 0.14 0.14 0.15 0.17 0.19 0.19 0.21 0.21 0.22 0.23 0.26 0.26 0.27 0.28 0.30 0.31 0.33 0.34 0.35 0.35 0.40 0.40 0.41 0.42 0.44 0.44 0.45 0.46 0.46 0.49 0.50 0.52 0.61 0.66 0.70 0.78 Subwatershed Nitrogen Loading Number (lb/acre/yr) MR13 MR16 BC13 MR18 MR22 MR15 MR19 MR12 UR13 MR05 MR09 MR14 BC04 UR05 BC14 MR17 BC01 UR14 UR10 MR11 BC05 MR06 MR21 MR02 BC02 BC10 UR11 BC12 MR01 MR03 UR03 UR09 MR20 MR10 UR08 UR12 UR04 BC09 BC07 BC11 BC08 UR07 BC03 UR02 BC06 UR01 UR06 MR04 MR08 MR07 1.68 1.69 1.72 2.05 2.09 2.17 2.25 2.50 2.54 2.60 2.67 2.68 2.69 2.70 2.70 2.72 2.74 2.75 2.77 2.80 2.83 2.83 2.84 2.84 2.89 2.96 2.96 2.98 2.98 3.00 3.00 3.04 3.10 3.10 3.20 3.23 3.30 3.36 3.37 3.52 3.55 3.57 3.60 3.79 3.79 5.28 5.30 5.66 6.37 8.43 Minimum 1st Quartile Median Value 3rd Quartile Maximum 1.68 2.70 2.96 3.36 8.43 F-3