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Draft Report Update
Recycled Water Master Plan
Prepared for
Big Bear Area Regional Wastewater Agency
122 Palomino Drive
Big Bear City, CA 92314
Revised September 2005
402 West Broadway Suite 1450
San Diego, CA 92101
DRAFT REPORT REVISED SEPTEMBER 2005
GEOHYDROLOGIC EVALUATION
OF ARTIFICIAL RECHARGE POTENTIAL
IN THE BIG BEAR VALLEY, CALIFORNIA
Prepared For:
Van Dusen Canyon
October 1, 2004
Prepared By:
GEOSCIENCE
GEOSCIENCE Support Services, Inc.
P.O. Box 220, Claremont, CA 91711
Tel: (909) 920-0707 Fax: (909) 920-0403
Spreading Basin
www.gssiwater.com
Geohydrologic Evaluation of Artificial Recharge Potential
in the Big Bear Valley, California
October 1, 2004
Prepared for
Dennis E. Williams, Ph.D.
Principal Hydrologist
Thomas Harder, R.G., C.HG
Senior Geohydrologist
Russell Kyle, R.G.
Staff Geohydrologist
GEOSCIENCE Support Services, Inc.
Tel: (909) 920-0707
Fax: (909)920-0403
Mailing: P.O. Box 220, Claremont, CA 91711
1326 Monta Vista Avenue, Suite 3, Upland, CA 91786
www.gssiwater.com
Geohydrologic Evaluation of Artificial Recharge Potential
in the Big Bear Valley, California 1-Oct-04
GEOHYDROLOGIC EVALUATION
OF ARTIFICIAL RECHARGE POTENTIAL
IN THE BIG BEAR VALLEY, CALIFORNIA
CONTENTS
1.0 EXECUTIVE SUMMARY................................................................................................. 1
2.0 INTRODUCTION............................................................................................................... 9
2.1 Background .................................................................................................................. 9
2.2 Purpose....................................................................................................................... 10
2.3 Project Location ......................................................................................................... 11
2.4 Definition of Terms.................................................................................................... 11
3.0 ARTIFICIAL SURFACE RECHARGE INVESTIGATION APPROACH ............... 18
3.1 Phased Approach........................................................................................................ 18
3.2 Preliminary Identification of Sites ............................................................................. 18
3.3 Site Access and Environmental Studies..................................................................... 20
3.4 Geohydrological Site Investigation Methodology ..................................................... 20
3.4.1 Exploratory Boreholes..................................................................................... 21
3.4.2 Shallow Subsurface Infiltrometer Testing....................................................... 21
3.4.3 Geohydrological Pilot Testing ........................................................................ 22
3.4.3.1 Monitoring Wells ................................................................................. 22
3.4.3.2 Spreading Basin Design and Construction........................................... 22
3.4.3.3 Surface Infiltration and Subsurface Percolation Testing...................... 23
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CONTENTS
(Continued)
4.0 GEOHYDROLOGIC SETTING..................................................................................... 24
4.1 Topography and Physiography .................................................................................. 24
4.2 Climate ....................................................................................................................... 24
4.2.1 Weather Patterns ............................................................................................. 25
4.2.2 Temperature .................................................................................................... 25
4.2.3 Precipitation .................................................................................................... 26
4.2.4 Evaporation ..................................................................................................... 27
4.3 Geology...................................................................................................................... 27
4.3.1 Bedrock Complex............................................................................................ 28
4.3.2 Alluvial Deposits............................................................................................. 29
4.4 Geohydrology............................................................................................................. 30
4.4.1 Watershed Boundaries and Hydrologic Subunits............................................ 30
4.4.2 Surface Water.................................................................................................. 30
4.4.3 Ground Water.................................................................................................. 31
4.4.3.1 Aquifer Systems ................................................................................... 32
4.4.3.2 Ground Water Flow.............................................................................. 33
4.4.3.3 Historical Ground Water Level Trends ................................................ 33
4.4.3.3.1 Erwin Hydrologic Subunit............................................................... 33
4.4.3.3.2 West Baldwin Hydrologic Subunit.................................................. 34
4.4.3.4 Natural Ground Water Recharge and Discharge .................................. 34
4.4.3.5 Ground Water Quality .......................................................................... 35
4.4.3.6 Existing Water Purveyors and Wells.................................................... 36
5.0 BOREHOLE DRILLING AND INFILTROMETER TESTING................................. 37
5.1 Green Spot Site .......................................................................................................... 37
5.1.1 Uncased Boreholes.......................................................................................... 37
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CONTENTS
(Continued)
5.1.2 Preliminary Infiltration Testing - Single-Ring Infiltrometers ......................... 39
5.2 Van Dusen Canyon Site ............................................................................................. 40
5.2.1 Uncased Boreholes.......................................................................................... 40
5.2.2 Preliminary Infiltration Testing - Single-Ring Infiltrometers ......................... 41
6.0 PILOT SCALE ARTIFICIAL RECHARGE TESTING .............................................. 42
6.1 Green Spot Site .......................................................................................................... 42
6.1.1 Monitoring Wells ............................................................................................ 42
6.1.1.1 Casing and Screen ................................................................................ 44
6.1.1.2 Filter Pack and Annular Seals .............................................................. 44
6.1.1.3 Soil Moisture Instrumentation.............................................................. 45
6.1.1.4 Surface Completions ............................................................................ 46
6.1.1.5 Development ........................................................................................ 46
6.1.1.6 Ground Water Quality Sampling.......................................................... 47
6.1.1.7 Monitoring Well Survey....................................................................... 48
6.1.2 Pilot Spreading Basin ...................................................................................... 48
6.1.2.1 Design and Construction ...................................................................... 48
6.1.2.2 Water Supply and Conveyance System................................................ 49
6.1.3 Pilot Infiltration Testing .................................................................................. 49
6.1.3.1 Inflow to Basin ..................................................................................... 49
6.1.3.2 Surface Water Depth ............................................................................ 50
6.1.3.3 Infiltration Rate - Soil Moisture Sensors.............................................. 50
6.1.3.4 Ground Water Elevations ..................................................................... 51
6.1.4 Ground Water Quality Sampling and Analysis............................................... 52
6.1.5 Ground Water Tracer Testing ......................................................................... 52
6.1.5.1 Method.................................................................................................. 53
6.1.6 Climatological Data......................................................................................... 54
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Geohydrologic Evaluation of Artificial Recharge Potential
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CONTENTS
(Continued)
6.2 Van Dusen Canyon .................................................................................................... 55
6.2.1 Monitoring Wells ............................................................................................ 55
6.2.1.1 Casing and Screen ................................................................................ 56
6.2.1.2 Filter Pack and Annular Seals .............................................................. 56
6.2.1.3 Soil Moisture Instrumentation.............................................................. 57
6.2.1.4 Surface Completions ............................................................................ 57
6.2.1.5 Development ........................................................................................ 58
6.2.1.6 Ground Water Quality Sampling.......................................................... 58
6.2.1.7 Monitoring Well Survey....................................................................... 59
6.2.2 Pilot Spreading Basin ...................................................................................... 59
6.2.2.1 Design and Construction ...................................................................... 59
6.2.2.2 Water Supply and Conveyance System................................................ 60
6.2.3 Pilot Infiltration Testing .................................................................................. 60
6.2.3.1 Inflow to Basin ..................................................................................... 60
6.2.3.2 Surface Water Depth ............................................................................ 61
6.2.3.3 Infiltration Rate - Soil Moisture Sensors.............................................. 62
6.2.3.4 Ground Water Elevations ..................................................................... 62
6.2.4 Ground Water Quality Sampling and Analysis............................................... 63
6.2.5 Ground Water Tracer Testing ......................................................................... 63
6.2.6 Climatological Data......................................................................................... 65
7.0 RESULTS OF ARTIFICIAL RECHARGE TESTING AT THE GREEN SPOT SITE
........................................................................................................................................... 66
7.1 Stratigraphy................................................................................................................ 66
7.1.1 Sediment Types ............................................................................................... 66
7.1.2 Correlation of Sediment Units ........................................................................ 67
7.2 Ground Water Occurrence and Flow ......................................................................... 68
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CONTENTS
(Continued)
7.2.1 Depth to Ground Water ................................................................................... 68
7.2.2 Ground Water Flow......................................................................................... 68
7.3 Surface Water Infiltration and Deep Percolation ....................................................... 69
7.3.1 Surface Water Infiltration and Subsurface Migration ..................................... 69
7.3.2 Estimates of Movement of Wetting Front in Vadose Zone ............................ 70
7.4 Impacts of Artificial Recharge on Ground Water Levels .......................................... 71
7.5 Impacts of Artificial Recharge on Ground Water Flow............................................. 71
7.6 Estimates of Ground Water Seepage Velocity........................................................... 72
7.6.1 Estimates Based On Geohydrologic Parameters............................................. 72
7.6.2 Estimates Based on Tracer Testing ................................................................. 75
7.7 Impacts of Artificial Recharge on Ground Water Quality......................................... 76
7.7.1 Baseline Ground Water Quality ...................................................................... 76
7.7.2 Pilot Test Source Water Quality...................................................................... 77
7.7.3 Post Recharge Ground Water Quality............................................................. 77
7.8 Pilot Basin Integrity ................................................................................................... 78
7.9 Results of Climatological Monitoring........................................................................ 79
7.9.1 Precipitation .................................................................................................... 79
7.9.2 Temperature .................................................................................................... 79
7.9.3 Wind Speed and Direction .............................................................................. 80
7.9.4 Evaporation ..................................................................................................... 80
8.0 RESULTS OF ARTIFICIAL RECHARGE TESTING AT THE VAN DUSEN
CANYON SITE ............................................................................................................... 81
8.1 Stratigraphy................................................................................................................ 81
8.1.1 Sediment Types ............................................................................................... 81
8.1.2 Correlation of Sediment Units ........................................................................ 82
8.2 Ground Water Occurrence and Flow ......................................................................... 82
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CONTENTS
(Continued)
8.2.1 Depth to Ground Water ................................................................................... 82
8.2.2 Ground Water Flow......................................................................................... 83
8.3 Surface Water Infiltration and Deep Percolation ....................................................... 83
8.3.1 Surface Water Infiltration and Subsurface Migration ..................................... 83
8.3.2 Estimates of Movement of Wetting Front in Vadose Zone ............................ 84
8.4 Impacts of Artificial Recharge on Ground Water Levels .......................................... 85
8.5 Impacts of Artificial Recharge on Ground Water Flow............................................. 86
8.6 Estimates of Ground Water Seepage Velocity........................................................... 86
8.6.1 Estimates Based On Geohydrologic Parameters............................................. 87
8.6.2 Estimates Based on Tracer Testing ................................................................. 88
8.7 Impacts of Artificial Recharge on Ground Water Quality......................................... 88
8.7.1 Baseline Ground Water Quality ...................................................................... 88
8.7.2 Pilot Test Source Water Quality...................................................................... 89
8.7.3 Post Recharge Ground Water Quality............................................................. 89
8.8 Pilot Basin Integrity ................................................................................................... 90
8.9 Results of Climatological Monitoring........................................................................ 91
8.9.1 Precipitation .................................................................................................... 91
8.9.2 Temperature .................................................................................................... 91
8.9.3 Wind Speed and Direction .............................................................................. 92
8.9.4 Evaporation ..................................................................................................... 92
9.0 GROUND WATER FLOW MODEL.............................................................................. 93
9.1 Conceptual Model ...................................................................................................... 93
9.2 Selection of Model Code............................................................................................ 93
9.3 Model Grid and Boundary Conditions....................................................................... 96
9.4 Aquifer Parameters .................................................................................................... 96
9.5 Recharge and Discharge............................................................................................. 97
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CONTENTS
(Continued)
9.5.1 General ............................................................................................................ 97
9.5.2 Streamflow Routing Package .......................................................................... 97
9.5.3 Recharge Package ........................................................................................... 98
9.5.4 Well Package Data .......................................................................................... 99
9.5.5 Drain Package ................................................................................................. 99
9.5.6 Evapotranspiration Package .......................................................................... 100
9.5.7 Constant Head Boundary .............................................................................. 100
9.6 Model Calibration .................................................................................................... 100
9.6.1 Model Calibration Period .............................................................................. 100
9.6.2 Calibration Process........................................................................................ 101
9.6.3 Model Calibration Results............................................................................. 101
9.6.3.1 Water Level Residuals........................................................................ 101
9.6.3.2 Ground Water Budgets ....................................................................... 102
10.0 CONCLUSIONS ............................................................................................................. 104
10.1 General ..................................................................................................................... 104
10.2 Green Spot Site ........................................................................................................ 105
10.3 Van Dusen Canyon Site ........................................................................................... 108
11.0 RECOMMENDATIONS................................................................................................ 111
12.0 REFERENCES................................................................................................................ 113
FIGURES, TABLES, PLATES, APPENDICES
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Geohydrologic Evaluation of Artificial Recharge Potential
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FIGURES
No. Description
1 General Location – Big Bear Valley
2 Recharge Site Evaluation Process
3 Photograph of Borehole Drilling
4 Photograph of Single-Ring Infiltrometer Testing
5 Photograph of Monitoring Well Construction
6 Photograph of Pilot Spreading Basin Construction
7 Conceptual Diagram of Pilot Recharge Test
8 Isoheyetal Map – Big Bear Lake and Baldwin Lake Watersheds
9 Annual Precipitation and Cumulative Departure From Mean Precipitation – Big Bear
Lake Dam Weather Station
10 Annual Precipitation and Cumulative Departure From Mean Precipitation – Big Bear
City Community Services District Weather Station
11 Geologic Setting - Big Bear Lake and Baldwin Lake Watersheds
12 Erwin Hydrologic Subunit Ground Water Elevations – February 2004
13 West Baldwin Hydrologic Subunit Ground Water Elevations – February 2004
14 Ground Water Production – 2003
15 Water Quality Trilinear Diagram
16 Detailed Site Map – Green Spot Site
17 Area Map – Van Dusen Canyon
18 Detailed Site Map – Van Dusen Canyon
19 Technical Cross Section – GS MW-1
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FIGURES
(Continued)
No. Description
20 Photograph of Soil Moisture Instrumentation
21 Photograph of Data Logger
22 Green Spot Pilot Spreading Basin – Design Schematic
23 Photograph of Green Spot Project Area
24 Green Spot Basin Inflow (19-Feb to 15-Mar)
25 Photographs of SF6 Tracer Injection Systems
26 Photograph of Weather Station and Class A Evaporation Pan
27 Technical Cross Section – VDC MW-1
28 Van Dusen Canyon Pilot Spreading Basin – Design Schematic
29 Photograph of Van Dusen Canyon Project Area
30 Van Dusen Canyon Basin Inflow (15-Mar to 19-Apr)
31 Mechanical Grading Analysis of Selected Soil Samples – Green Spot Springs Site
32 Green Spot Site – Ground Water Elevation Contour Map, Pre-Recharge Test –
February 12, 2004
33 Soil Moisture Sensors (GS MW-1)
34 Infiltration Rates (Calculated From GS MW-1 Soil Moisture Sensor Data)
35 Basin Infiltration Rate and Water Level Depth – Green Spot Area
36 Hydrographs – Green Spot Area
37 Green Spot Site – Ground Water Elevation Contour Map, Maximum Mound –
March 16, 2004
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Geohydrologic Evaluation of Artificial Recharge Potential
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FIGURES
(Continued)
No. Description
38 Green Spot Site – Ground Water Elevation Contour Map, Post-Recharge Test –
July 1, 2004
39 Trilinear Diagram - Background Water Quality – Green Spot Area
40 Trilinear Diagram - Post Recharge Ground Water Quality – Green Spot Area
41 Precipitation – Green Spot Weather Station
42 Temperature – Green Spot Weather Station
43 Wind Speed and Direction – Green Spot Weather Station
44 Evaporation – Green Spot Area Class A Evaporation Pan
45 Mechanical Grading Analysis – Van Dusen Canyon Site
46 Van Dusen Canyon Site – Ground Water Elevation Contour Map – Pre-Recharge Test –
February 23, 2004
47 Soil Moisture Sensors (VDC MW-1)
48 Infiltration Rates (Calculated From VDC MW-1 Soil Moisture Sensor Data)
49 Basin Infiltration Rate and Water Level Depth – Van Dusen Canyon Area
50 Hydrographs – Van Dusen Canyon
51 Van Dusen Canyon Site – Ground Water Elevation Contour Map, Maximum Mound –
April 30, 2004
52 Van Dusen Canyon Site – Ground Water Elevation Contour Map, Post-Recharge Test –
July 1, 2004
53 Trilinear Diagram – Background Water Quality – Van Dusen Canyon
54 Trilinear Diagram – Post Recharge Ground Water Quality – Van Dusen Canyon
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Geohydrologic Evaluation of Artificial Recharge Potential
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FIGURES
(Continued)
No. Description
55 Precipitation – Van Dusen Canyon Weather Station
56 Temperature – Van Dusen Canyon Weather Station
57 Wind Speed and Direction – Van Dusen Canyon Weather Station
58 Evaporation – Van Dusen Canyon Class A Evaporation Pan
59 Green Spot Area Ground Water Model Grid
60 Green Spot Area Ground Water Model Boundary Conditions
61 Comparison of Measured and Model-Generated Ground Water Levels – Model
Calibration (1992-2004)
62 Green Spot Area Ground Water Model Hydrographs
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Geohydrologic Evaluation of Artificial Recharge Potential
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TABLES
No. Description
1 Site Evaluation Matrix
2 Summary of Annual Evaporation Data – BBCCSD Weather Station
3 Summary of Uncased Borehole and Well Completion Data
4 Summary of Infiltrometer Data
5 List of Laboratory Water Quality Analytes – Ground Water Sampling
6 Summary of Water Quality Laboratory Results – Green Spot Site
7 Ground Water Level Measurements and Elevations – Green Spot Site
8 Summary of Sulfur Hexafluoride Tracer Data
9 Summary of Water Quality Laboratory Results – Van Dusen Canyon Site
10 Ground Water Level Measurements and Elevations – Van Dusen Canyon Site
11 Summary of Seepage Velocity Calculations – Green Spot Site
12 Summary of Seepage Velocity Calculations – Van Dusen Canyon Site
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PLATES
No. Description
1 Generalized Geohydrologic Cross-Sections – Green Spot Site
2 Generalized Geohydrologic Cross-Sections – Van Dusen Canyon Site
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APPENDICES
Ltr. Description
A Ground Water Elevation Data
B Lithologic Log and Well Construction Logs
C Sieve Analyses
D Geophysical Logs
E Monitoring Well As-Built Diagrams
F Soil Moisture Data
G Ground Water Quality Laboratory Reports
H Basin Inflow and Surface Water Data
I Weather Station Data and Evaporation Pan Data
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GEOHYDROLOGIC EVALUATION
OF ARTIFICIAL RECHARGE POTENTIAL
IN THE BIG BEAR VALLEY, CALIFORNIA
1.0 EXECUTIVE SUMMARY
The Big Bear Area Regional Wastewater Agency (BBARWA) is currently investigating the
feasibility of using advanced treated recycled water from their treatment plant near Big Bear
City, California as a supplemental source of artificial surface recharge to the aquifers in the
Baldwin and Big Bear Lakes area of western San Bernardino County, California. Currently,
approximately 2,200 acre-ft/yr of secondarily treated (recycled) water from the plant is being
exported out of the Big Bear area to Lucerne Valley via a pipeline. This recycled water has been
identified as a potential supplemental supply to artificially recharge the ground water resources
in the area. The water would be applied to spreading basins1 within the Baldwin and Big Bear
Lakes area and, thus, would be a benefit by providing supplemental recharge to the aquifers
within the basin.
The purpose of this report is to describe the technical studies, analytical methods and results of
an artificial surface recharge feasibility study to assess areas within Big Bear Valley that are
promising for full-scale artificial surface recharge operations. A phased site investigation
approach was developed that included preliminary reconnaissance and identification of multiple
sites for further investigation, site access and environmental issues, preliminary investigations
and borehole drilling, regulatory requirements, and pilot testing. Four sites were initially
identified for investigation of artificial recharge potential:
1
Surface spreading basins are used to artificially recharge the aquifer system.
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Geohydrologic Evaluation of Artificial Recharge Potential
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• The area north of Green Spot Spring (Erwin Subunit; Eastern Baldwin Lake Watershed),
• Van Dusen Canyon (West Baldwin Subunit; Western Baldwin Lake Watershed),
• Shay Meadow Area (Erwin Subunit; central Baldwin Lake Watershed), and
• Sand Canyon (Rathbone Subunit; Eastern Big Bear Lake Watershed).
As a result of the phased investigation process, the Shay Meadow and Sand Canyon sites were
removed from consideration before any field investigations were conducted. The Green Spot
Spring and Van Dusen Canyon sites were the subjects of further drilling and testing.
A total of ten uncased exploratory boreholes (five at the Green Spot Site and five at the
Van Dusen Canyon Site) were drilled to enable the collection of soil lithologic data to provide a
preliminary indication of the permeability of the unsaturated zone between the land surface and
the ground water table. In addition, single ring infiltrometer tests were conducted at each site
(five at the Green Spot Site and three at the Van Dusen Canyon Site) to provide a preliminary
indication of surface infiltration rates. Based on these investigations, it was determined that the
majority of sediments beneath the Green Spot and Van Dusen Canyon sites consisted of
permeable sediments (i.e. sand and gravel) conducive to artificial recharge of surface water.
Based on these findings, it was decided to proceed with artificial recharge pilot tests at each site.
The surface recharge pilot tests included the recharge of potable water in one-quarter acre
surface spreading basins. The pilot tests were designed to assess percolation rates of recharge
water, impacts of recharge on ground water levels, and migration characteristics of the stored
water. Five monitoring wells were installed at each site to enable the collection of ground water
level and quality data before, during and after the tests. One monitoring well at each site was
equipped with soil moisture sensors designed to track the percolation of water in the subsurface
during the tests. In addition, a tracer was added to the recharge water to provide supplemental
data on the rate of ground water movement beneath each site.
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Geohydrologic Evaluation of Artificial Recharge Potential
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Potable water from the BBCCSD distribution system2 was introduced to the Green Spot Site
pilot recharge basin between February 17, and March 15, 2004 at a rate of approximately
160 gpm. Analysis of the drilling and pilot recharge testing at this site resulted in the following
conclusions:
• The Green Spot site is located on recent alluvial deposits of permeable sand and
gravel.
• No laterally extensive fine-grained (i.e. silt and/or clay) layers were observed
beneath the site that would inhibit the downward percolation of recharge water
from the ground surface to the ground water table.
• Ground water occurs at approximately 100 ft bgs, which allows adequate space
for mounding and storage of recharge water.
• Following approximately one month of artificial recharge testing at an inflow rate
of approximately 160 gpm, water was successfully introduced into the subsurface
via the pilot recharge basin at the Green Spot Site, creating a measurable ground
water mound.
• The artificial recharge rate measured from the pilot recharge test ranges from
3.1 to 3.7 ft/day. For planning purposes, the long-term recharge rate should be
assumed to be approximately one-half of the observed rate from the pilot recharge
test, to account for periodic reductions in recharge rate that can be anticipated due
to clogging. Clogging results from the gradual accumulation of fine-grained
(i.e. silt) sediments and/or algae on the bottom of the spreading basins, which
decreases their ability to facilitate recharge. This decrease in recharge rate is
restored through periodic basin maintenance.
2
Although the potable water for the test was provided from the BBCCSD distribution system, both the
BBCCSD and BBDWP contributed water for the test.
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Geohydrologic Evaluation of Artificial Recharge Potential
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• The effective porosity of unsaturated sediments beneath the site was estimated to
be approximately 9 percent.
• The hydraulic conductivity3 of the aquifer beneath the site was estimated to be
approximately 110 gpd/ft2 or 15 ft/day.
• The maximum ground water mound measured directly beneath the spreading
basin (GS MW-1) was approximately 17 ft. The greatest ground water level
increase was measured in the furthest downgradient monitoring well at the site
(GS MW-2S). The reason for the large increase at GS MW-2S is unknown but
may be geologically influenced.
• The ground water mound created by the recharge test extended beyond the
monitoring network at the Site. A localized shift in the ground water flow
direction (from north-northwest to west-northwest) was noted in the immediate
vicinity of the pilot spreading basin.
• The ground water gradient beneath the Green Spot Site increased during the
artificial recharge test from 0.06 ft/ft measured prior to the recharge test to
0.128 ft/ft measured during the period of maximum ground water mound height.
• Ground water quality was not adversely affected by the artificial recharge pilot
test.
• Ground water seepage velocities estimated based on geohydrologic data obtained
from the recharge test range from approximately 5 ft/day (based on static ground
water levels) to 11 ft/day (based on the hydraulic gradient measured during
maximum ground water mound height).
• At the seepage velocities estimated from the artificial recharge test data, ground
water recharged at the Green Spot Site would reach the nearest production wells
3
Hydraulic conductivity is a measure of the ability of the soil to transmit water. It is dependant upon both
the properties of the soil and those of the fluid.
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Geohydrologic Evaluation of Artificial Recharge Potential
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(BBDWP’s Lakewood well field) in 8.5 to 17.5 months. Based on these
estimates, the California Department of Health Services (DHS) criteria of
6 months of subsurface residence time for a recycled water recharge project
would be met.
• Supplemental data on seepage velocities are being obtained via a tracer test.
However, the tracer test is ongoing and will be summarized later in a technical
memorandum separate from this report.
Potable water from the BBCCSD distribution system4 was introduced to the Van Dusen Canyon
Site pilot recharge basin between March 15, and April 19, 2004 at a rate of approximately
63 gpm. The pilot recharge testing at this site resulted in the following conclusions:
• The Van Dusen Canyon site is located on recent alluvial deposits of permeable
sand and gravel.
• Some laterally extensive fine-grained (i.e. silt and/or clay) layers were observed
in the subsurface to the south of the recharge basin site that may inhibit the
downward percolation of recharge water from the ground surface to the ground
water table.
• Ground water occurs at approximately 100 ft bgs, which allows adequate space
for mounding and storage of recharge water.
• Following approximately one month of artificial recharge testing at an inflow rate
of approximately 60 gpm, water was successfully introduced into the subsurface
via the pilot recharge basin at the Van Dusen Canyon site, creating a measurable
ground water mound.
4
Although the potable water for the test was provided from the BBCCSD distribution system, both the
BBCCSD and BBDWP contributed water for the test.
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Geohydrologic Evaluation of Artificial Recharge Potential
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• The artificial recharge rate measured from the pilot recharge test ranges from
1.1 to 1.6 ft/day. For planning purposes, the long-term recharge rate should be
assumed to be approximately one-half of the observed rate from the pilot recharge
test, to account for periodic reductions in recharge rate that can be anticipated due
to clogging. Clogging results from the gradual accumulation of fine-grained (i.e.
silt) sediments and/or algae on the bottom of the spreading basins, which
decreases their ability to facilitate recharge. This decrease in recharge rate is
restored through periodic basin maintenance.
• The effective porosity of unsaturated sediments beneath the site was estimated to
be approximately 4 percent.
• The hydraulic conductivity of the aquifer beneath the site was estimated to be
approximately 70 gpd/ft2 or 9 ft/day.
• The maximum ground water mound measured directly beneath the spreading
basin (VDC MW-1) was approximately 7.5 ft. The greatest ground water level
increase was measured in the monitoring well at the center of the recharge basin
(VDC MW-1).
• The ground water gradient beneath the Van Dusen Canyon site increased during
the artificial recharge test from 0.0009 ft/ft measured prior to the recharge test to
0.0025 ft/ft measured during the period of maximum ground water mound height.
• Ground water quality was not adversely affected by the artificial recharge pilot
test.
• Ground water seepage velocities estimated based on geohydrologic data obtained
from the recharge test range from approximately 0.9 ft/day (based on static
ground water levels) to 1.4 ft/day (based on the hydraulic gradient measured
during maximum ground water mound height).
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• At the seepage velocities estimated from the artificial recharge test data, ground
water recharged at the Van Dusen Canyon site would reach the nearest production
well (BBCCSD Well No. 1) in approximately 106 to 160 months. Given these
findings, additional extraction wells could be constructed closer to the recharge
site to take advantage of the recycled water while adhering to DHS subsurface
residence time requirements.
• Supplemental data on seepage velocities are being obtained via a tracer test.
However, the tracer test is ongoing and will be summarized later in a technical
memorandum separate from this report.
Based on the results and conclusions of the geohydrological investigation presented in this
report, GEOSCIENCE recommends the following with regard to development of full-scale
artificial recharge programs at the Green Spot and Van Dusen Canyon sites:
• Based on the geohydrologic data collected during this investigation, it is
recommended to continue pursuing full-scale artificial recharge programs at both
the Green Spot and Van Dusen Canyon sites. No fatal flaws that would warrant
discontinuing this process were identified as a result of the artificial recharge pilot
tests.
• The Van Dusen Canyon Site is a valid candidate for a full-scale artificial recharge
program. However, given the lower recharge rates and limited available property,
this site is not as favorable as the Green Spot Site.
• Based on the artificial recharge rates measured during the Green Spot test, the
property necessary to support a full-scale program at this site should include at
least five acres of area for surface water spreading, plus the necessary additional
land for berms and maintenance access. Although this area would not be utilized
at all times, it would allow for the rotation of basins for maintenance.
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• In support of long-term coordination with the DHS, it is recommended to
continue analyzing ground water samples from the monitoring wells at the site for
the tracer. Although the likelihood and timing of detecting the tracer in the
downgradient monitoring wells and/or production wells is unknown, if detected, it
would provide valuable supplemental support for the existing ground water
seepage velocity estimates.
To facilitate future planning for the storage and recovery of artificially recharged water at the
Green Spot site, GEOSCIENCE developed a ground water flow model of the northern
Erwin Subunit. Results of the transient calibration indicate a relatively good match between
model-generated and measured ground water levels, particularly the magnitude of the ground
water mounding generated during the Pilot Scale Artificial Recharge Testing. Given the
acceptable calibration of the Green Spot ground water flow model, it is recommended to evaluate
different artificial recharge scenarios using the model to assess the amounts of recycled water
that can be recharged and the pumping regimes that are realistic to recover the stored water in the
northern Erwin Subunit. Ideally, these “put” and “take” scenarios would be developed in
conjunction with the local water purveyors.
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2.0 INTRODUCTION
2.1 Background
The Big Bear Area Regional Wastewater Agency (BBARWA) is currently investigating the
feasibility of using advanced treated recycled water from their treatment plant near Big Bear
City, California as a supplemental source of artificial recharge to the aquifers in the Baldwin and
Big Bear Lakes area of western San Bernardino County (Big Bear Valley; see Figure 1). The
volume of secondarily treated recycled water produced at the BBARWA treatment plant in 2001
ranged from approximately 1.7 million gallons per day (MGD) (October) to 2.9 MGD (March)
with an average of approximately 2 MGD (approximately 2,200 acre-ft/yr). This recycled water
from the plant is currently exported out of the Big Bear area to Lucerne Valley via a pipeline.
Historically, municipalities within the Big Bear Valley have met municipal water demand with
local ground water and spring water resources that are replenished from precipitation within the
Baldwin Lake and Big Bear Lake watersheds. The ground and surface water resources are
limited, however, and the demand for water in the area periodically exceeds the supply,
particularly in “ dry” years or during periods of prolonged below-average precipitation. With no
imported water currently available, the area is in need of other sources of water supply to meet
demand.
Recycled water from BBARWA’s treatment plant near Big Bear City has been identified as a
potential supplemental supply to artificially recharge the ground water resources in the area. The
secondarily treated water would be further treated through a process of microfiltration, reverse
osmosis and ultraviolet radiation before being applied to surface spreading basins within the
Baldwin and Big Bear Lakes area. In so doing, the advanced treated recycled water would
provide a benefit by supplementing the natural recharge to the aquifers within the basin.
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An initial geohydrologic review of potential artificial recharge sites in the Baldwin and Big Bear
Valley identified four areas, which showed merit for further consideration:
• The area north of Green Spot Spring,
• Van Dusen Canyon,
• Shay Meadow Area, and
• Sand Canyon.
2.2 Purpose
Before implementing a full-scale artificial recharge program in the Big Bear Valley, it was
necessary to assess the feasibility of artificial recharge in this area from a geohydrological
perspective. Three fundamental questions needed to be addressed:
1) Where are the best areas in Big Bear Valley where surface water will percolate to
ground water?
2) Once stored, what are the parameters governing movement underground?
3) Will migration of recharged water meet the DHS requirements regarding
minimum residence time within the subsurface?
The purpose of this report is to describe the basis and results of the geohydrological investigation
to determine the feasibility of using the artificial surface recharge method to supplement ground
water supply, and to provide answers to the above questions. The report will address the
planning, pilot test design, pilot test implementation and results, and integration of the ground
water flow model.
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2.3 Project Location
The Big Bear Lake and Baldwin Lake drainage basins or watersheds (referred herein as the Big
Bear Valley) encompass an area of approximately 73 square miles and are situated within the
San Bernardino Mountains of Southern California (see Figure 1). The valley is located
approximately 90 miles east of Los Angeles and 25 miles northeast of San Bernardino and is a
popular resort and recreation spot. The four sites considered as part of the artificial recharge
evaluation are located within the central and eastern portions of Big Bear Valley (see Figure 1).
2.4 Definition of Terms
The principle definitions used in this report were taken from California Department of Water
Resources (CDWR), 1975, from the Handbook of Hydrology (Maidment, 1993), or from the
Dictionary of Geological Terms, 3rd edition (Bates et al., 1984). In some cases, authors have
expanded or clarified terms consistent with industry standards.
Alluvium A geologic term describing beds of sand, gravel, silt, and
clay deposited by flowing water.
Alluvium (upper) Sand, gravel, silt, and clay deposits of recent geologic age.
Alluvium (lower) Sand, gravel, silt, and clay deposits with an age range of
hundreds of thousands to more than one million years.
Aquifer A geologic formation or group of formations which store,
transmit, and yield significant quantities of water to wells
and springs. See also “ confined aquifer,” “ unconfined
aquifer,” and “ semiconfined aquifer” .
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Aquitard A less permeable geologic unit which stores, but does not
readily transmit, water.
Confined Aquifer A permeable geologic unit located beneath a relatively
impermeable unit.
Conceptual Model An hypothesis regarding how the hydrogeologic systems
work. It consists of basic elements such as inflow,
outflow, and system geometry.
Depression Storage Water temporarily stored on the surface in low areas, or
depressions.
Effective Porosity A fraction of the void space which forms part of the
interconnected flow paths through the medium, per unit
volume of porous medium (excluding void space in
isolated or dead-end pores). Also known as “ specific
yield.”
Evaporation The rate of liquid water transformation to vapor from open
water, bare soil, or vegetation with soil beneath. The
process by which water is changed from the liquid or solid
state into the gaseous state through the transfer of heat
energy.
Evapotranspiration That portion of precipitation that is returned to the air
through direct evaporation or by transpiration of
vegetation. No attempt is being made to distinguish
between the two.
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Extraction Generally refers to the pumping of ground water from
wells.
Fault A fracture in the earth’s crust, with displacement of one
side of the fracture with respect to the other.
Formation A geologic term that designates a body of rock or
rock/sediment strata of similar lithologic type or
combination of types.
Ground Water Water contained in interconnected pores located below the
water table in an unconfined aquifer or located in a
confined aquifer.
Head Energy, produced by elevation, pressure, or velocity,
contained in a water mass.
Hydraulic Conductivity The measure of the ability of the soil to transmit water,
dependent upon both the properties of the soil and those of
the fluid.
Hydraulic Gradient The rate of change in total head per unit distance of flow in
a given direction (e.g. the slope of the water table).
Hydrology The origin, distribution, and circulation of water of the
earth, including precipitation, stream flow, infiltration,
ground water storage, and evaporation.
Infiltration The process of water entry into the soil surface from
rainfall, snowmelt, or irrigation and the subsequent
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percolation downward through the soil. (Stored soil water
may be consumptively used by vegetation, may percolate
further downward to ground water storage, or may exit the
soil surface as seeps or springs.)
Leaky Aquifer An aquifer bound by one or two aquitards. Also known as
a “ semiconfined aquifer.”
Maximum Perennial Yield The maximum quantity of ground water perennially
available if all possible methods and sources are developed
for recharging the basin. However, this quantity depends
upon the amount of water economically, legally, and
politically available to water purveyors.
Out-Flowing Seepage The slow movement of ground water from a basin or
aquifer to a collection point such as a surface water lake or
dry lake.
Overdraft The temporary condition of a ground water basin where the
amount of water withdrawn by pumping exceeds the
amount of water replenishing the basin over a period of
time.
Percolation The predominantly vertical migration of water through
permeable soil or other geologic formations to the ground
water table.
Permeability The capability of soil or other geologic formations to
transmit water. The term is used to separate the effects of
the medium from those of the fluid on the hydraulic
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conductivity.
Playa The geological term for the flat and generally barren lower
portions of arid basins having internal drainage which
periodically flood and accumulate sediment (i.e. dry lake).
Potential Evaporation The quantity of water evaporated per unit area, per unit
time, from an idealized, extensive, free water surface under
existing atmospheric conditions.
Recharge Flow to ground water storage from precipitation,
infiltration from streams, and other sources of water.
Recoverable Water The sum of surface runoff (stream flow adjusted for
anthropogenic diversions and storage, if any) and
underflow (ground water).
Safe Yield The maximum quantity of water that can be continuously
withdrawn from a ground water basin without adverse
effects. Due to its vague definition and the implication of a
fixed quantity of extractable water based on the average
annual basin recharge, the term has fallen into disfavor as
compared to the term “ maximum perennial yield.”
Semiconfined Aquifer An aquifer bound by one or two aquitards. Also known as
a “ leaky aquifer.”
Soil Moisture Percentages Percentages of moisture in the soil, based on the weight of
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oven-dry material.
Specific Storativity The volume of water that a unit volume of porous medium
releases from or takes into storage per unit change in
hydraulic head.
Storativity The volume of water that an aquifer releases or takes into
storage per unit change in hydraulic head.
Total Dissolved Solids (TDS) The quantity of minerals (salts) in solution in water.
Total Porosity. Fraction of void space per unit volume of porous medium
Transmissivity Rate of flow of water through an aquifer. The product of
hydraulic conductivity and the layer thickness.
Transpiration. That part of the total evaporation which enters the
atmosphere from the soil through the plants; the process by
which water vapor escapes from a living plant and enters
the atmosphere; the evaporation of water absorbed by the
crop and transpired and water used directly in the building
of plant tissue, in a specified time
Unconfined Aquifer A permeable geologic unit with the water table forming its
upper boundary.
Vadose Zone The partially saturated or unsaturated regions between the
ground surface and the water table.
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Water Table The surface where ground water is encountered in a water
well in an unconfined aquifer.
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3.0 ARTIFICIAL SURFACE RECHARGE INVESTIGATION APPROACH
3.1 Phased Approach
A phased site investigation approach was developed to sequentially answer the questions and
address the other issues relevant to assessing the feasibility of an artificial surface recharge
program in Big Bear Valley. The approach sequence included preliminary reconnaissance and
identification of multiple sites for further investigation, site access and preliminary
environmental studies, borehole drilling, assessment of regulatory requirements, and
geohydrological pilot testing (see Figure 2) for recharge potential.
The project was phased so that critical issues that would curtail consideration of candidate sites
for further investigation could be identified early in the investigation process. The phases
became increasingly intrusive and complex as the viability of the sites for artificial recharge
became more evident.
3.2 Preliminary Identification of Sites
In identifying potential artificial recharge sites for further investigation, a number of key site
evaluation criteria were examined:
• Presence/absence of site-wide impermeable layers;
• Vadose zone permeability;
• Proximity to existing or proposed hydraulically downgradient production wells;
• Depth to ground water;
• Regulatory requirement issues or local restraints;
• Area available for full-scale spreading basins.
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The criteria were used to evaluate three sites in the Baldwin Lake area (the area north of
Green Spot Spring, Van Dusen Canyon, and Shay Meadow; see Figure 1). A fourth site,
Sand Canyon, was later added for consideration. Sources of information in reviewing the sites
included aerial photographs, geologic maps, geologic reports on the area, driller’s logs on file
with the State of California Department of Water Resources, field inspection, and data provided
by the Big Bear City Community Services District (BBCCSD) and the City of Big Bear Lake
Department of Water and Power (BBDWP). A comprehensive list of publications considered
during the initial identification of sites is provided in Section 12.0.
Using the site evaluation criteria, candidate sites were evaluated and ranked according to their
relative viability as potential recharge sites (see Table 1; GEOSCIENCE, 2001). Each of the six
siting criteria (site-wide impermeable layers, depth to ground water, etc.) was given a weighting
factor based on importance of the criterion and expressed as a percentage. For example, the
presence or absence of site-wide impermeable layers was considered the most important factor
and, thus, was given the highest weighting factor. The three potential sites were then assessed
individually as to their respective site-specific criteria. The product of the individual
site-specific raw score and the respective weighting factors were totaled to obtain the total
weighted score for each site.
From the evaluation, the two most viable sites for further investigation were the Green Spot
Springs and Van Dusen Canyon sites. The Sand Canyon site, although not a part of the
GEOSCIENCE, 2001 study, was also given consideration based on the results of test drilling
conducted previously in this area (GEOSCIENCE, 1991). However, this site was removed from
consideration prior to further testing due to site access constraints and regulatory issues. The
Shay Meadow site was not considered viable due to shallow ground water and environmental
concerns.
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3.3 Site Access and Environmental Studies
Once sites within Big Bear Valley were chosen for further investigation, specific parcels of land
were identified to conduct drilling and geohydrological pilot testing. Local municipalities with
property in these areas were approached first because access agreements would be relatively
easy. In this way, the Van Dusen Canyon site was successfully identified on approximately
3.8 acres owned by BBCCSD. In the proposed Green Spot site, no property owned by local
municipalities or public agencies was available, so private property owners were approached to
obtain access. In this way, an agreement with a property owner in the Green Spot area was
reached prior to conducting the testing.
In accordance with the California Environmental Quality Act (CEQA), an initial study was
required for the sites to identify potential environmental impacts and possible mitigation of the
proposed drilling and pilot testing. In addition to satisfying California law, the initial
environmental study was also directed to identify sensitive species or historical sites that would
render a full-scale artificial recharge project infeasible. The results of the initial environmental
study showed that pilot testing at any of the sites would not present any significant
environmental impact. The initial study was completed on August 22, 2003 by Tom Dodson &
Associates, 2003 and approved by the BBARWA Board on September 24, 2003.
3.4 Geohydrological Site Investigation Methodology
With sites identified for further geohydrological investigation, field investigation procedures
were specifically designed for each site. Individual field investigation procedures were tailored
to each particular site, given the availability of existing data, knowledge of the site, anticipated
subsurface characteristics, and availability of land for access.
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3.4.1 Exploratory Boreholes
Because no detailed lithologic data were available for the Green Spot and Van Dusen Canyon
sites, the first phase of work was to drill boreholes at the sites to obtain soil samples, which when
analyzed would enable a general understanding of the relative permeability of the sediments. A
relatively high percentage of silt and clay (impermeable sediments) would not be favorable while
a relatively high percentage of sand and gravel (permeable sediments) would be favorable for
artificial surface recharge. Boreholes were drilled using dual-tube reverse air circulation drilling
technology (see Figure 3). In addition to visually logging soil samples collected during drilling,
selected samples were analyzed for grain size distribution (mechanical grain size analysis).
Geophysical borehole logging was another important characterization tool that was utilized in
each borehole. Geophysical logs provide important data regarding bed boundaries, relative
permeability of sediments, location of the ground water surface, location of perched aquifers, and
consolidated or cemented layers. When used in conjunction with a lithologic log, they can
enable a very comprehensive stratigraphical description of the subsurface.
3.4.2 Shallow Subsurface Infiltrometer Testing
To provide a general indication of potential surface water infiltration rates and to evaluate spatial
variations in infiltration rates throughout each site, localized field testing using single-ring
infiltrometers was conducted at each of the two sites. Five infiltrometer tests were performed at
the Green Spot site (GS I-1 through GS I-5) and three at the Van Dusen Canyon site
(VDC I-1 through VDC I-3) in accordance with Bouwer (1998; see Figure 4). Locations for
infiltrometer testing were selected away from borehole locations to maximize the amount of data
collected across each site.
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3.4.3 Geohydrological Pilot Testing
The final phase of the ground water replenishment sub-scale pilot geohydrological study was the
design and implementation of surface recharge pilot tests at each of the two sites. The pilot tests
included the surface recharge of potable water in sub-scale one-quarter acre surface spreading
basins for an extended period of time. The pilot tests were designed to measure percolation rate
of recharge water, the effect of recharge on ground water levels, and sub-surface migration
characteristics of the added water at each recharge site.
3.4.3.1 Monitoring Wells
Prior to conducting artificial surface recharge testing, a comprehensive monitoring network was
designed and installed at each site to monitor the advancing flow of surface water to the ground
water and changes in ground water levels and ground water quality during the pilot test. Soil
moisture measurement instrumentation was installed at specific depth intervals in a borehole
drilled at the approximate center of each pilot basin using the dual-tube percussion hammer
drilling method. These boreholes were also completed as 2-inch diameter monitoring wells.
Other monitoring wells were also drilled and constructed in the areas immediately surrounding
the pilot spreading basins using the dual-tube reverse air circulation and mud rotary drilling
methods (see Figure 5).
3.4.3.2 Spreading Basin Design and Construction
At each of the two selected recharge sites, a one-quarter acre, bermed pilot spreading basin was
designed and constructed to facilitate the recharge testing (see Figure 6). Each pilot basin
included an inlet pipeline from the BBCCSD distribution system to allow for the spreading of
potable water during the test. The pipelines enter each pilot basin and terminate at 12-inch
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diameter vertical stand pipes which are open at the top. Rip rap was placed around the base of
each stand pipe to prevent the scouring of the basin bottoms and excessive suspension of fine
grained material within the standing water. During the pilot testing, water flowed into the stand
pipe from the conveyance pipeline, out of the top of the stand pipe, and over the rip rap into the
spreading basin.
3.4.3.3 Surface Infiltration and Subsurface Percolation Testing
The pilot recharge tests were conducted at each of the sites to assess percolation rates (see
Figure 7 for a conceptual diagram of a pilot recharge test). In addition to monitoring percolation
rates and ground water level changes, ground water samples were collected from the monitoring
wells prior to and following the recharge testing to assess the ground water quality both before
and after pilot recharge testing. In addition, a tracer was added to the recharge water to provide
supplemental data on the rate of ground water movement beneath each site.
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4.0 GEOHYDROLOGIC SETTING
4.1 Topography and Physiography
Big Bear and Baldwin Lakes are situated at an elevation of approximately 6,740 and 6,700 ft
above mean sea level (amsl), respectively. They are located in the San Bernardino Mountains
within the Transverse Ranges geomorphic province of Southern California (Figure 1) within a
continuous east-west valley that extends from the west end of Big Bear Lake to the east end of
Baldwin Lake. The surrounding mountain slopes are relatively steep (as much as 70 degrees)
and rugged. Prominent mountain peaks and ridges in the surrounding area include
Delamar Mountain (8,398 ft amsl), Bertha Ridge (8,201 ft amsl), Gold Mountain (8,235 ft amsl),
and Nelson Ridge (6,998 to 7,232 ft amsl) to the north; and Deadman’s Ridge (7,212 to
7,602 ft amsl), Moon Ridge (7,583 to 7,866 ft amsl), Sugarloaf Mountain (9,952 ft amsl),
Snow Summit (8,182 ft amsl), and Clark’s Summit (7,816 ft amsl) to the south. Big Bear Lake
receives surface runoff from several small canyons and valleys, the most prominent of which are
Grout Creek to the northwest, Van Dusen Canyon to the northeast, Sawmill Canyon to the
southeast, Sand Canyon to the southeast, Knickerbocker Canyon and Metcalf Creek to the south,
and North Creek to the southwest. Baldwin Lake receives runoff from Van Dusen Canyon to the
northwest, Mt. Doble Valley to the north, Pioneertown Valley to the southeast, Shay Creek to the
south, and Sawmill Canyon to the southwest.
4.2 Climate
The Big Bear Lake area is generally characterized as cool (California Division of Mines and
Geology [CDMG], 1954; Crippen, 1965), based primarily on average annual temperature and
precipitation. The area is classified as humid because winter precipitation provides more water
to the root zone of plants than the plants can absorb (Thornthwaite, 1948).
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4.2.1 Weather Patterns
Seasonal weather patterns in the San Bernardino Mountains are primarily controlled by
semipermanent high and low pressure systems located over North America and the
Pacific Ocean. During the summer months, the semipermanent high pressure cell, the
Pacific High (centered over the Pacific Ocean about 1,600 miles west of the California coast)
diverts low-pressure, moisture-carrying weather systems north of California. This cell contracts
and moves southward during the winter months, allowing Pacific storms to cross over California,
from the west, thus providing the majority of the winter moisture to the San Bernardino
Mountains. During the summer months, a seasonal low-pressure weather cell (the California
Low) develops over Southern California resulting in a predominantly on-shore flow of air from
the ocean. Occasionally these summer conditions result in short-lived thunderstorms forming
over the mountain areas, providing small amounts of precipitation.
4.2.2 Temperature
Air temperature in the higher elevations of the San Bernardino Mountains follows a normal
pattern of high summer and low winter readings. Winter temperatures are considerably lower
than those recorded in the lower basin areas of Southern California (San Bernardino and
Los Angeles) primarily due to the higher elevation. Average daily temperatures in winter
generally range from about 35 to 40 degrees Fahrenheit (Crippen, 1965). Summer mountain
temperatures, however, are only slightly lower than basin temperatures with average daily
readings ranging from about 60 to 70 degrees Fahrenheit (Crippen, 1965).
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4.2.3 Precipitation
Annual precipitation amounts in the Big Bear Lake area were based on data collected at the
Big Bear Lake Dam and BBCCSD rain gauges (see Figure 8). From 1951 through 2003,
precipitation at the Big Bear Lake Dam ranged from 8.60 inches (2002) to 84.54 inches
(1993; see Figure 9). Average annual precipitation at the dam for the period of record is
34.64 inches per year. Annual precipitation recorded at the BBCCSD rain gauge over the same
period of record ranged from 3.8 (1955) to 34.79 inches (1952; see Figure 10). The average
annual precipitation at the BBCCSD gauge is 13.75 inches per year. Precipitation amounts at the
west end of Big Bear Lake are significantly higher than those recorded in the Baldwin Lake area
(see Figure 8) due to the rainshadow effect of the mountains on storms migrating inland from the
Pacific Ocean.
Historical annual precipitation and cumulative departure from mean precipitation for the
Big Bear Lake Dam are shown on Figure 9. The severity and extent of dry and wet periods can
be readily observed from the plot of the cumulative summation of departures of annual
precipitation from the long-term mean precipitation. The data indicate five cyclical variations in
the precipitation pattern from 1951 to 2003:
1) 1951-1965: 15 years of below normal precipitation;
2) 1966 to 1983: a wet period interrupted by an 8 year dry period from 1970 to 1977;
3) 1984 to 1992: 9 years of below normal precipitation;
4) 1993 to 1998: a 6 year wet period; and
5) 1999 to 2003: a period of below normal precipitation.
Historical annual precipitation and cumulative departure from mean precipitation for the
Big Bear City Community Services District Station are shown on Figure 10. The data indicate
four cyclical variations in the precipitation pattern from 1951 to 2003:
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1) 1951 to 1954: a wet period;
2) 1955 to 1976: a 22 year period of below normal precipitation;
3) 1977 to 1998: a wet period interrupted by a 3 year dry period from 1990 to 1992; and
4) 1999 to 2003: a period of below normal precipitation.
4.2.4 Evaporation
Historically, evaporation rates in the Big Bear area have been measured using an evaporation pan
located near BBCCSD Well No. 4 (see Figure 8). Evaporation at this station is generally higher
(approximately 35 inches per year) during the summer and fall months and is minimal (less than
0.2 inches per year) during the winter months.
Typically, estimates of evaporation in the Big Bear area have been made during the eight months
of the year when temperatures are predominantly above freezing, allowing measurements to be
made. Measurements from the BBCCSD evaporation pan made during the summer months from
1993 and 1997 were combined with estimates of evaporation for snow pack at high elevations
(Maidment, 1993). The resulting estimate of average annual evaporation for the period from
1993 to 1997 is 42.4 inches per year (see Table 2). Average monthly evaporation rates range
from less than 0.2 inches per month in the winter months to as much as 8.4 inches per month in
the summer.
4.3 Geology
The San Bernardino Mountains formed as a result of uplift along a complex system of faults,
including the San Andreas Fault System, which separates the San Bernardino Mountains from
the neighboring San Gabriel Mountains to the west. The majority of the tectonic activity that
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created the mountains occurred during Late Pliocene and Pleistocene times (approximately 3.6 to
0.011 million years before present). However, the June 28, 1992 Big Bear earthquake is
reflective of the continued tectonic activity in the area.
The most significant fault in the vicinity of the San Bernardino Mountains is the San Andreas
Fault zone, which is strike-slip in nature and bounds the mountains on the south side. A
significant zone of frontal reverse faults exists on the north side of the mountains. These faults
account for much, if not all, of the uplift in the San Bernardino Mountains (Miller, 1987).
4.3.1 Bedrock Complex
Precambrian bedrock in the Big Bear area consists predominantly of Baldwin Gneiss and Late
Precambrian quartzite (SLW), referred to as the Saragosa Quartzite (Johnson, 1994; Guillon,
1954; see Figure 11).
Paleozoic rocks consist of Cambrian and uppermost Precambrian metasedimentary rocks
comprised of crystalline limestone and marble (FCT). These rocks outcrop in the Bertha Ridge
area northwest of Big Bear City Airport, in the Gold Mine Ski area southwest of Moonridge, and
northeast of Baldwin Lake.
Mesozoic intrusive rocks (Mzp) in the area are comprised primarily of quartz monzonite and
quartz diorite. They occur throughout much of the Big Bear area and can be found to the south,
southwest, west, and northwest of Big Bear Lake. These rocks do not yield major quantities of
water but some slant wells have been drilled into this formation and are being used for water
supply. Water is yielded from these rocks presumably along fractures.
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4.3.2 Alluvial Deposits
Alluvial deposits in the Big Bear area include five groups: Alluvial fan gravel (Qaf), Landslide
deposits (Qls), Pleistocene to Recent Lake and Meadow deposits (Qal), Pleistocene to Recent
alluvium and colluvium (Qaa), and Pleistocene older surficial deposits (Qof; see Figure 11). The
groupings have been chosen, in part, to correspond to designations from earlier work
(Law Environmental, 1989). A more detailed and comprehensive treatment of the alluvium is
provided in Sadler (1982) who differentiated the alluvium into alluvial fan gravels, alluvium and
colluvium, wind blown sand, and lake and meadow deposits with further differentiation based on
relative age, sediment composition and activity.
The most recent deposits in the Big Bear area are alluvial lake and meadow deposits (Qal), are
located in the immediate vicinity of Baldwin and Erwin Lake, and consist primarily of
non-organic and organic-rich clay (Johnson, 1994). At the margins of the lakes, the clay
sediments are interbedded with the alluvium extending from the surrounding mountains. The
thickness of the clay ranges from nothing at the margins of Baldwin Lake to more than 270 ft as
determined from driller’ s logs (Johnson, 1994). The clay does not transmit appreciable amounts
of water and serves as a confining layer in places where it is stratigraphically over more
permeable alluvial sediments at depth.
Pleistocene to Recent alluvial and colluvial deposits (Qaa) underlie the Qal. These deposits
consist of poorly sorted, unconsolidated, intermixed and interlayered clay, silt, sand, and gravel
ranging from approximately 10 ft to a maximum of approximately 150 ft in thickness. Qaa
deposits are found in stream channels, valley floors, and flood plains.
The Pleistocene Older surficial deposits (Qof) underlie the Qaa and unconformably overlie
basement plutonic and metamorphic rocks. They consist of glacial till, terrace gravel, Older
terrace gravel deposits, and fanglomerate deposits. Lithologies consist of loosely consolidated,
intermixed and interlayered gravel, sand, silt and clay. Thickness ranges from several feet near
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contact with the basement rocks, to greater than 1,000 ft in the center of the valley, and the hills
in and around the Moonridge and Sugarloaf areas.
4.4 Geohydrology
4.4.1 Watershed Boundaries and Hydrologic Subunits
Big Bear Valley has been divided into two major watersheds; the Big Bear Lake Watershed at
the west end of the valley and the Baldwin Lake Watershed at the east end of the valley. The
Big Bear Lake Watershed covers an area of approximately 38.5 square miles and delineates the
area where surface water drains into Big Bear Lake. The Big Bear Lake Watershed has been
divided into seven subareas or hydrologic subunits: Gray’ s Landing, Grout Creek, North Shore,
Division, Rathbone, Village, and Mill Creek (see Figure 1; LeRoy Crandall & Associates, 1987).
The subareas are delineated based on surface water drainage divides.
The Baldwin Lake Watershed covers an area of approximately 34.3 square miles and delineates
the area where surface water drains into Baldwin Lake. This watershed is divided into four
subareas or hydrologic subunits: Erwin, West Baldwin, East Baldwin, and Van Dusen
(see Figure 1; LeRoy Crandall & Associates, 1987).
4.4.2 Surface Water
The largest surface water body in Big Bear Valley is Big Bear Lake. This lake covers a surface
area of approximately 2,860 acres and was formed in 1884 with the construction of a dam across
Bear Creek, a tributary to the Santa Ana River. The lake has a maximum depth of 72 ft when
lake levels are at their highest. Baldwin Lake is the second most significant surface water body
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in Big Bear Valley although it is considered a mountain playa and seasonally contains standing
water. The surface area of this lake is approximately 1,500 acres (Johnson, 1994).
Surface water drains into Big Bear Lake via numerous small creeks that surround the lake. The
most predominant are Rathbone Creek in the southeastern portion of the watershed, and
Grout Creek in the northwestern portion of the watershed. In the Baldwin Lake watershed,
prominent drainages include Green Canyon Creek and Van Dusen Canyon, both of which drain
toward Baldwin Lake.
Surface water in the Green Spot area occurs as spring flow and in ephemeral drainages during
short periods of heavy precipitation. Springs that may contribute to inflow are: Green Spot
Spring (see Figure 12), a number of springs located south of the project area shown on Figure 12
(including Fish Hatchery Spring), and unnamed springs east of Shay Pond in the Shay Meadow
area (see Figure 12). Many of the springs have measurable flow at least part of the year. Green
Spot and Fish Hatchery Springs (Erwin Subunit) typically flow year-round and are used by
BBCCSD to supplement ground water production. When present, surface water exits the
drainage basin north of Shay Pond via Shay Creek, which flows northwards into Baldwin Lake.
Surface water flow within the Van Dusen Canyon area originates as runoff and/or spring flow
along Caribou Creek and its tributaries and flows south and southeastward into Big Bear City
(see Figure 13). Within Big Bear City, the natural drainage system has been altered by urban
development, but seasonal runoff generally flows eastward into Baldwin Lake.
4.4.3 Ground Water
Ground water in the Big Bear area generally occurs in the unconsolidated alluvial deposits on the
lower slopes of the surrounding mountains and in the fractures and weathered portions of the
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bedrock. Following the convention of Law Environmental, 1989, the aquifers can generally be
grouped into three units: an upper aquifer, middle aquifer, and lower aquifer.
4.4.3.1 Aquifer Systems
The upper aquifer consists of recent alluvium which typically consists of more permeable
sediments (sand and gravel) that transmit water more readily. This aquifer extends throughout
the Baldwin Lake area, thinning to the west and north and thickening to the east (Baldwin Lake
Playa). In the Big Bear Lake area, the upper aquifer is generally less than 60 ft thick and is not
typically saturated. The upper aquifer is typically unconfined.
The middle aquifer consists of older alluvium and older fan deposits consisting of sand, gravel,
silt, and clay in varying amounts and proportions. This aquifer extends throughout the area to
the south of Big Bear Lake and Baldwin Lake and ranges from approximately 250 ft thick
(Mill Creek subunit) to greater than 800 ft thick (Division, West Baldwin, and Erwin subunits).
Ground water in the middle aquifer is semi-confined to confined.
A lower aquifer has been identified in the central portions of Big Bear Valley. The lower aquifer
has been encountered in the Baldwin Lake area at depths ranging from 400 to 670 ft with a
thickness of approximately 120 to 200 ft (GEOSCIENCE, 2000; GEOSCIENCE, 2003b;
GEOSCIENCE, 2003c). In the Mill Creek subunit (western Big Bear Lake watershed) the lower
aquifer is between 380 and 490 ft bgs (GEOSCIENCE, 2004b). The lithology consists of
varying amounts of gravel, coarse sand, pebbles, and interbedded sandy clay. Ground water in
the lower aquifer is typically confined.
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4.4.3.2 Ground Water Flow
Ground water flows by gravity drainage from areas of high elevation (the mountain slopes) into
areas of low elevation, ultimately collecting in the sediments beneath Big Bear Lake and
Baldwin Lake. All ground water flow within the Big Bear Lake Watershed is toward Big Bear
Lake. Ground water flow within Baldwin Lake Watershed is toward Baldwin Lake.
4.4.3.3 Historical Ground Water Level Trends
4.4.3.3.1 Erwin Hydrologic Subunit
Ground water levels for the Erwin and Vaqueros monitoring wells are plotted on Figure 12 from
data summarized in Appendix A. Water levels measured in the Erwin monitoring well, which is
located at a higher elevation, fluctuate seasonally to a greater degree than the Vaqueros
monitoring well located at a lower elevation. The water levels generally correlate with annual
precipitation with peak water levels occurring during winter months and the highest peaks
occurring during years with relatively high annual precipitation. The exception to this
correlation is a significant water level drop (approximately 30 ft) in the Erwin monitoring well in
1992; a year with relatively average precipitation amounts. The water level drop is coincident
with the Big Bear earthquake and suggests a connection between the hydrology of the watershed
and the geologic structure of the basin. The nature of the connection, however, is unclear.
Ground water levels in both the Erwin and Vaqueros monitoring wells are at their lowest
elevation since late 1992 and have been declining since early 1999. The declining ground water
level trends correspond with below normal precipitation conditions experienced in the Big Bear
area since 1999.
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4.4.3.3.2 West Baldwin Hydrologic Subunit
Ground water levels for the Greenway Park, Airport, Hillendale, and Maltby monitoring wells as
well as BBCCSD Well No. 5 (which is not pumped) are plotted on Figure 13. Water levels
measured in all of these monitoring wells generally correlate very well with one another and with
annual precipitation patterns: peak water levels occurring during winter months and the highest
peaks occurring during years with relatively high annual precipitation.
Water levels in all of the monitoring wells are at their lowest elevation since the early 1990s and
have been declining since mid 1998, which corresponds with ongoing below normal
precipitation in the Big Bear area.
4.4.3.4 Natural Ground Water Recharge and Discharge
Natural replenishment of ground water resources in the Big Bear Lake Watershed occurs from
both surface runoff and percolation of precipitation. The majority of the rainfall in the lower
basin elevations (valleys) is evaporated or taken up by plants before it enters the ground water
system. The primary sources of replenishment to the ground water basins are infiltration of
precipitation at the higher basin elevations and surface water infiltration in the streams and
drainages during major storm events or prolonged periods of high precipitation.
Natural ground water discharge from the Erwin Subunit is via evapotranspiration from the
Shay Meadow area and Erwin Lake during periods of high ground water levels and ground water
underflow to the aquifer beneath Baldwin Lake. During periods of high ground water levels, the
ground water table intersects the land surface in Shay Meadow, feeding the springs and ponds in
that area. This surface water is subject to evaporation to the atmosphere and utilization by
plants. During periods when the ground water level is below the land surface, the
evapotranspiration decreases with depth.
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Ground water discharge from the Erwin Subunit also occurs through ground water pumping from
municipal and private wells. The distribution of annual ground water pumping from municipal
wells within the Baldwin Lake watershed during the year 2003 is shown on Figure 14
(information from private well owners was not available). In the vicinity of the Van Dusen
Canyon site, the majority of pumping occurs at the Division well field on the eastern shores of
Big Bear Lake (North Shore and Division subunits), and from a cluster of BBCCSD wells west
of Baldwin Lake (West Baldwin subunit). In the vicinity of the Green Spot site (Erwin subunit),
the majority of ground water pumping is from the BBDWP Maple Well to the west and from the
BBDWP Lakewood well field located approximately 3,000 ft northwest of the Green Spot site.
4.4.3.5 Ground Water Quality
Shallow ground water within the Big Bear Lake and Baldwin Lake watersheds is generally of
calcium bicarbonate type (see Figure 15). Water quality, in terms of total dissolved solids
(TDS), is considered very good with concentrations ranging from approximately 90 to
460 milligrams per liter (mg/L). There are no significant differences in TDS concentration
between springs and wells screened in the alluvial aquifers.
Ground water in deeper aquifers typically contain a higher percentage of sodium relative to
calcium and have higher concentrations of naturally occurring fluoride and/or arsenic. Fluoride
has been detected in ground water wells throughout the Big Bear Lake and Baldwin Lake
watersheds but is most prevalent in the central valley area between Big Bear and Baldwin Lakes
(GEOSCIENCE, 2001a; GEOSCIENCE, 2000). Arsenic concentrations are highest in the
aquifers of the Mill Creek subunit (GEOSCIENCE 2003a). Fluoride concentrations as high
as 13 mg/L have been detected in samples from the Riffenburgh Monitoring Well
(Division Subunit; GEOSCIENCE, 2003a).
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4.4.3.6 Existing Water Purveyors and Wells
Two municipal water purveyors exist within the Big Bear Valley area: BBCCSD and BBDWP.
Both purveyors own and operate production and monitoring wells within the valley.
BBCCSD currently operates and/or maintains 10 vertical production wells (BBCCSD
Well Nos. 1, 1B, 3, 3A, 3B, 4, 4A, 6, 9, and 10) within the West Baldwin Hydrologic Subunit
and 2 ground water monitoring wells (Greenway and Maltby monitoring wells). Within the
Erwin Hydrologic Subunit, BBCCSD has one vertical production well (BBCCSD Well No. 2),
2 monitoring wells (Erwin and Vaqueros monitoring wells), and 2 modified springs (Green Spot
Spring and Fish Hatchery Spring). BBDWP currently operates and/or maintains 8 vertical
production wells within the Erwin Hydrologic Subunit (Lakewood Well Nos. 3, 5, 6, and 7, the
Maple Well, the Monte Vista Well, Onyx Well No. 5, and the Skyview Well). The Lakewood
well field is located closest to the Green Spot site, approximately 3,000 ft hydraulically
downgradient.
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5.0 BOREHOLE DRILLING AND INFILTROMETER TESTING
To determine if pilot scale artificial recharge testing was warranted at the Green Spot and
Van Dusen Canyon sites, a preliminary field investigation was conducted as an empirical
evaluation of the relative permeability of the sediments beneath each site. The field investigation
consisted of the following:
• Drilling of five (5) uncased boreholes at both the Green Spot and Van Dusen Canyon
sites;
• Collection and classification of soil samples from each borehole;
• Collection of downhole geophysical logs from each borehole; and
• Single-ring infiltrometer testing at five (5) locations throughout the Green Spot site and
three (3) locations throughout the Van Dusen Canyon site.
The initial field investigation began on October 8, 2003 with borehole drilling at the Green Spot
site and was completed on January 27, 2004 at the Van Dusen Canyon site.
5.1 Green Spot Site
5.1.1 Uncased Boreholes
Five uncased boreholes (GS BH-1 through GS BH-5) were drilled in and around the Green Spot
site by Layne Christensen Company of Fontana, California during the month of October 2003
(see Figure 16). The uncased boreholes were drilled to enable the collection of data to assess the
subsurface stratigraphy of the vadose zone (i.e. in saturated sediments between the ground
surface and the water table). The 5.25-inch diameter boreholes were drilled using the dual tube
reverse circulation drilling method to depths ranging from 95 to 142 ft bgs (see Table 3).
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Soil samples were collected for classification at 5-ft intervals and placed in 1-gallon sealable
plastic bags. Each bag was properly labeled in the field with the boring number, sample depth
interval, and date of collection. Samples were classified using the Unified Soil Classification
System (USCS). Lithologic logs for the uncased boreholes are provided in Appendix B.
Selected soil samples were further analyzed for grain size distribution by mechanical grading
analysis. This procedure involves pouring a sample through a series of sieves of differing
aperture to assess the relative percentages of each grain size in the sample. Samples selected for
analysis generally represented each of the soil types encountered during drilling to provide a
comparison of grain size distribution for the different soil types. GEOSCIENCE conducted all
mechanical grading analyses in accordance with ASTM D422-63 (2002). Mechanical grading
analysis plots are provided in Appendix C.
At the completion of drilling, bentonite mud was circulated throughout each borehole in order to
stabilize it for the geophysical logs. The geophysical logs were performed by Pacific
Surveys, Inc., of Claremont, California and are provided in Appendix D. Logs included the
following:
• 16-inch and 64-inch normal resistivity with point resistance;
• Spontaneous potential (SP);
• Focused guard resistivity (Laterolog);
• Acoustic (sonic); and
• Gamma ray.
Geophysical logs were obtained in all boreholes except for GS BH-5. The geophysical logs
could not be obtained in GS BH-5 because large cobbles from the borehole walls fell into the
borehole during the logging process.
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Upon completion of geophysical logging, all uncased boreholes were filled with
cement-bentonite grout from total depth to the ground surface in accordance with
San Bernardino County requirements.
Review of the samples collected during the borehole drilling program indicated that the majority
of sediments beneath the Green Spot site consisted of permeable sediments (i.e. sand and gravel)
conducive to artificial recharge of surface water (see Appendix B; Plate 1). Only minor amounts
of fine-grained sediments (silt and clay) were identified in the boreholes. Furthermore, few
fine-grained layers that would inhibit the downward percolation of surface water were identified
from the geophysical logs. Based on these findings, it was decided to proceed with an artificial
recharge pilot test at the Green Spot site.
5.1.2 Preliminary Infiltration Testing - Single-Ring Infiltrometers
From November 25 through December 10, 2003, five infiltrometer tests (GS I-1 through GS I-5)
were performed at locations throughout the Green Spot site (see Figure 16).
Localized field testing using a single-ring infiltrometer was conducted to provide an approximate
measure of the surface water infiltration rate and to evaluate variation in surface water
infiltration rates throughout the area of investigation. The infiltrometer consisted of a thin
walled steel cylinder measuring 12 inches high and 24 inches in diameter. At each test location,
the upper 4 to 6 inches of soil was removed and the cylinder was pushed into the ground
approximately 1 inch. The cylinder was then filled with approximately 10 inches of water which
was allowed to infiltrate into the ground. The cylinder was refilled periodically until a combined
total of approximately 20 inches of water had infiltrated or 6 hours had elapsed, whichever came
first. Lowering water levels within the cylinder were timed throughout the course of the test. In
cases were residual standing water was left within the cylinder after 6 hours had elapsed, the
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actual cumulative amount of infiltrated water was recorded and the remaining water was bailed
out.
After the infiltration portion of the test was complete, the cylinder was removed and the area
around the test site was excavated with a shovel to determine the lateral and vertical extent of the
wetting front. All infiltrometer testing was performed and evaluated in accordance with
Bouwer (1998). Results of the testing are summarized in Table 4.
5.2 Van Dusen Canyon Site
5.2.1 Uncased Boreholes
Five uncased boreholes (VDC BH-1 through VDC BH-5) were drilled at the Van Dusen Canyon
site by Layne Christensen Company of Fontana, California during the month of December 2003
(see Figure 17). The uncased boreholes were drilled using the same drilling method as used for
the Green Spot site (see Section 5.1.1). Borehole depths at the Van Dusen Canyon site ranged
from 95 to 125 ft bgs (see Table 3).
Soil samples were collected, classified, and analyzed (mechanical grading analysis) at the
Van Dusen Canyon site as described in Section 5.1.1. Lithologic logs for the Van Dusen Canyon
uncased boreholes are provided in Appendix B. Mechanical grading analyses are provided in
Appendix C.
At the completion of drilling, geophysical logs were obtained from the uncased boreholes as
described in Section 5.1.1. The geophysical logs are provided in Appendix D.
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Upon completion of geophysical logging, all uncased boreholes were filled with
cement-bentonite grout from total depth to the ground surface in accordance with
San Bernardino County requirements.
Review of the samples collected during the borehole drilling program indicated that the majority
of sediments beneath the Van Dusen Canyon site consisted of permeable sediments (i.e. sand and
gravel) conducive to artificial recharge of surface water (see Appendix B; Plate 1). Only minor
amounts of fine-grained sediments (silt and clay) were identified in the boreholes. Furthermore,
few fine-grained layers that would inhibit the downward percolation of surface water were
identified from the geophysical logs. Based on these findings, it was decided to proceed with an
artificial recharge pilot test at the Van Dusen Canyon site.
5.2.2 Preliminary Infiltration Testing - Single-Ring Infiltrometers
Preliminary infiltration testing was conducted at three locations at the Van Dusen Canyon site
(VDC I-1 through VDC I-3; see Figure 18) from December 2 through December 17, 2003. All
infiltration testing was performed in accordance with Bouwer, 1998 as described in
Section 5.1.2. Results of the infiltration testing are summarized in Table 4.
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6.0 PILOT SCALE ARTIFICIAL RECHARGE TESTING
Based on the results of the borehole drilling program, it was decided to proceed with
constructing the monitoring features and testing facilities necessary to conduct pilot scale
recharge tests at both the Green Spot and Van Dusen Canyon sites. The overall purpose of the
pilot tests was to provide a comprehensive evaluation of artificial recharge potential at the two
sites. Specifically, the pilot infiltration tests were designed to develop design parameters for the
full-scale basins, assess the impacts of artificial recharge on ground water levels, and evaluate
the rate and direction of ground water movement during recharge operations. Pilot scale
recharge testing included the following tasks:
• Locating, drilling, constructing, and developing monitoring wells;
• Locating, designing, and constructing a pilot scale infiltration basin;
• Collecting background ground water levels prior to initiating the infiltration testing;
• Monitoring surface water inflow to the basin and surface water depth within the basin
during recharge testing;
• Collecting ground water level and soil moisture data during the infiltration testing;
• Collecting ground water quality data before and after recharge testing;
• Conducting recharge water tracer testing; and
• Collecting climatological data.
6.1 Green Spot Site
6.1.1 Monitoring Wells
Five monitoring wells (GS MW-1 to GS MW-5) were drilled and installed at the Green Spot site
from October 2003 through January 2004 (see Figure 16). Two additional monitoring wells
(GS MW-6 and GS MW-7) were drilled and installed in June 2004 approximately midway
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between the Green Spot pilot test site and the BBDWP Lakewood production wells. With the
exception of GS MW-1, pilot boreholes for the monitoring wells were drilled using a dual tube
reverse circulation drilling rig equipped with a 5 ¼-inch diameter bit. Each monitoring well pilot
borehole was then reamed to 12 ¼-inches diameter using the mud rotary drilling method. The
instrumented monitoring well (GS MW-1) was completed within a 10 ¾-inch diameter borehole
drilled using the dual tube percussion hammer drilling method.
Soil samples were collected for classification during the drilling at each pilot borehole at 5-ft
intervals. Each sample was placed in 1-gallon sealable plastic bags which were properly labeled
in the field with the boring number, sample depth interval, and date of collection. Samples were
classified using the Unified Soil Classification System (USCS). Lithologic logs for the
monitoring well boreholes are provided in Appendix B.
At the completion of drilling, geophysical logs were performed in each borehole by Pacific
Surveys., Inc, of Claremont, California and are provided in Appendix D. Logs included the
following:
• 16-inch and 64-inch normal resistivity with point resistance;
• Spontaneous potential (SP);
• Focused guard resistivity (Laterolog);
• Acoustic (sonic); and
• Gamma ray.
Due to the nature of the drilling method geophysical logs could not be performed in the
instrumented monitoring well borehole (GS MW-1).
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6.1.1.1 Casing and Screen
With the exception of GS MW-1 and GS MW-2, monitoring wells were completed with 4-inch
diameter schedule 40 PVC blank and perforated well casing. The screened portion of each well
casing was perforated with 0.020-inch horizontal slots.
GS MW-1 was constructed with 2-inch diameter schedule 40 PVC blank and perforated well
casing to a depth of 145 ft. The screened portion of the well casing, from 100 to 140 ft bgs, was
perforated with 0.020-inch horizontal slots.
GS MW-2 was constructed as a nested monitoring well with two lengths of schedule 40 PVC
casing and screen. The shallow well (GS MW-2S) was constructed to a total depth of 145 ft bgs
and was perforated with 0.020-inch horizontal slots from 100 to 140 ft bgs. The deep well
(GS MW-2D) was constructed to a total depth of 215 ft bgs and was perforated with 0.020-inch
horizontal slots from 170 to 210 ft bgs.
Well completion details for each monitoring well are shown in Table 3 and in Appendix E.
6.1.1.2 Filter Pack and Annular Seals
The annular space between the borehole wall and well casing of monitoring wells GS MW-3, 4,
5, 6 and 7 was filled with RMC Lonestar® #3 sand from the well bottom to approximately
50 ft bgs. The filter pack was placed in the annulus of all wells by pumping through a tremie
pipe using clear water as a circulating medium. With the exception of GS MW-1, all wells were
completed with an annular seal, consisting of a sand-cement slurry, which was pumped through a
tremie pipe from the top of the uppermost filter pack to the ground surface.
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The annular space within the dual completion monitoring well (GS MW-2) was filled with RMC
Lonestar® #3 sand from the bottom of the well at 220 ft bgs to 159 ft bgs (GS MW-2D) and from
146 ft bgs to 54 ft bgs (GS MW-2S). An annular seal was installed from 146 to 159 ft bgs,
between the two perforated intervals, to prevent hydraulic communication between the shallow
and deep aquifers in the borehole. This allowed for the monitoring of aquifer-specific ground
water levels and quality.
The instrumented monitoring well (GS MW-1) had RMC Lonestar® #3 sand installed within the
annular space from the bottom of the well at 147 ft bgs to 98 ft bgs, just above the perforated
interval. RMC Lonestar® #30 sand was installed surrounding each soil moisture sensor,
approximately 3 ft above and 3 ft below, and a 4-ft bentonite seal was installed between each
(see Figure 19).
6.1.1.3 Soil Moisture Instrumentation
Soil moisture sensors were attached to the blank casing of GS MW-1 to allow for the collection
of data relative to the percolation rate within the vadose zone. The soil moisture sensors consist
of two concentric electrodes embedded in a granular reference matrix material. The matrix
material is surrounded by a synthetic membrane for protection. An internal gypsum tablet
buffers the system against salinity variation from the infiltrating water. The sensors measure
water potential, generally quantified in kOhms. Low soil resistance readings would indicate a
saturated soil while high resistance would indicate a relatively dry soil.
Watermark® soil moisture sensors (see Figure 20) were attached to the side of the 2-inch
diameter schedule 40 PVC casing at 10 ft intervals from 15 to 95 ft bgs (see Figure 19). The
annular space surrounding each sensor was filled with RMC Lonestar® #30 sand. A 4-ft
bentonite seal was placed between each sensor to ensure that basin water does not preferentially
migrate through the borehole.
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The electrical wire leads from the sensors were labeled prior to installation to ensure proper
depth placement. In addition, the surface exposures of the leads were labeled and marked to
identify the depth of each individual soil moisture sensor. The leads were extended through PVC
pipe to a data logger, located outside of the pilot basins.
Each depth specific sensor was attached to a properly labeled port on an AM416 multiplexer.
The multiplexer was connected to a data logger (CR23X; see Figure 21) set to collect readings
every 10 minutes. Readings were stored within the data logger in units of kOhms (resistance)
and were downloaded at least weekly during testing.
Soil moisture data from the pilot recharge test are provided in Appendix F.
6.1.1.4 Surface Completions
Monitoring wells GS MW-6 and GS MW-7 were completed at the surface with 11 ¾-inch
diameter flush mounted, traffic-rated well vaults set within concrete. All other monitoring wells
were completed with 8 5/8-inch OD steel monument-style protective well covers with lockable
lids. The protective well covers were cemented in place around the well, leaving approximately
2 to 3 ft of stick up above the finished surface of the concrete well pad (see Appendix E).
6.1.1.5 Development
Each monitoring well was initially developed by bailing to remove any suspended material, then
by airlifting to remove colloidal and fine-grained sediments from within the well, filter pack, and
near well zone. For some wells, dispersing agents (NW220) were added to the wells prior to
development to assist in breaking down and removing drilling mud from the well and near-well
zone. Final development was conducted using a 2-inch diameter submersible pump.
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Development continued until at least three well volumes of ground water had been discharged
from the well and when the turbidity was measured to be less than or equal to 5 nephelometric
turbidity units (NTU).
GS MW-1 was not developed as pilot basin construction was underway and the well could not be
accessed by the development rig.
6.1.1.6 Ground Water Quality Sampling
Immediately following the well development process, ground water samples were collected from
each well and submitted to E. S. Babcock & Sons, Inc., a State of California certified laboratory,
for water quality analysis. The samples were collected in laboratory prepared bottles and stored
on ice until delivered to the laboratory. Chain-of-custody protocol was followed at all times
during the collection, storage, and delivery of the ground water samples. Immediately prior to
sampling, the total dissolved solids (TDS), pH, and temperature of the ground water was
measured and recorded.
Results were used to establish the baseline water quality condition of the ground water in the
area. Ground water from GS MW-1 was not sampled as pilot basin construction was underway
and the well could not be accessed by the development rig.
A summary of constituents analyzed are summarized in Table 5 (see Appendix G for laboratory
reports).
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6.1.1.7 Monitoring Well Survey
Following construction and development of the monitoring wells, the top of casing at each
monument was surveyed by Joseph E. Bonadiman & Associates, Inc., of San Bernardino,
California, a California licensed surveyor. The survey was conducted relative to an established
benchmark. Top of casing elevations were surveyed to the nearest 0.01-ft.
6.1.2 Pilot Spreading Basin
The Green Spot pilot scale artificial recharge test was conducted within an approximate
one-quarter acre spreading basin located on the northwest corner of Shady and Willow Lanes
(see Figure 16).
6.1.2.1 Design and Construction
The pilot spreading basin was an approximately one-quarter acre area surrounded by earthen
berms. Excavated material generated during basin construction was excavated and used to
construct the surrounding berms. The inside walls of the pilot basin were constructed with a
slope gradient of approximately 3:1. The top of the berms were approximately 12 ft wide to
allow vehicle access. Figure 22 shows the schematic for the pilot basin design.
The pilot basin design included an inlet pipeline to allow for the spreading of water during the
test. The PVC pipeline was oriented east-west, leading from Willow Lane to the southeast
portion of the basin where it terminated at a 12-inch diameter vertical stand pipe that was open at
the top. Rip rap was placed around the base of the stand pipe to prevent scour of the basin
bottom and excessive suspension of fine grained material within the standing water in the basin.
During the pilot testing, water flowed into the stand pipe from the conveyance pipeline, out of
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the top of the stand pipe, and over the rip rap into the basin. A photograph of the Green Spot site
is shown on Figure 23.
6.1.2.2 Water Supply and Conveyance System
Water was supplied to the pilot basin via a 4-inch diameter PVC schedule 40 conveyance
pipeline and a 4-inch diameter fire hose connected to an existing BBCCSD fire hydrant located
along Willow Lane. The pipeline was located aboveground and was designed to supply as much
as 200 gpm to the basin. An inline instantaneous flowmeter equipped with a totalizer was
attached to the pipeline to enable monitoring of water inflow to the basin.
6.1.3 Pilot Infiltration Testing
The Green Spot site recharge test was initiated on February 17, 2004 when potable water from
BBCCSD’ s distribution system was introduced into the pilot scale spreading basin. The recharge
portion of the test was conducted between February 17 and March 13, 2004 although ground
water level monitoring and other testing is ongoing.
6.1.3.1 Inflow to Basin
Inflow to the pilot recharge basin was monitored via an inline water flow meter within the water
supply conveyance pipeline. The instantaneous flow rate and total volume of water supplied to
the basin were monitored on a weekly basis and recorded on standard field data collection forms.
Whenever necessary, the dates and times when water supply to the basin was stopped and started
were also recorded. Data collected from the inline flow meter are provided in Appendix H and
summarized on Figure 24.
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Continuous filling of the Green Spot pilot infiltration basin began on February 17, 2004. The
instantaneous flow rate and cumulative volume of water as recorded at the in-line flow meter is
presented in Figure 24. The average discharge rate into the pilot basin was initially established
at approximately 66 gpm but was increased to approximately 164 gpm on February 27 as the
basin was not completely filling. At this flow rate, the water level in the basin rose to
approximately 1.4 ft and remained at that level throughout the duration of the test. On March 15,
the test was discontinued and water flow into the basin was turned off.
The quality of the source water used for the infiltration testing at the Green Spot site was
evaluated for comparison with the water quality of the ground water both prior to and after the
recharge test. A sample was collected from the fire hydrant source on May 7, 2004 and
submitted to E.S. Babcock & Sons, Inc., under chain-of-custody protocol on the same day it was
collected. The sample was transported in a cooler with ice and was analyzed for the constituents
listed in Table 5. A summary of the results of the analyses is provided in Table 6. Laboratory
reports are provided in Appendix G.
6.1.3.2 Surface Water Depth
The depth of surface water in the pilot basin was maintained at approximately 1.4 ft throughout
the recharge test. The surface water depth was measured at least twice per week using a
graduated staff gauge installed within the basin bottom and located near the instrumented
monitoring well. Staff gauge readings are provided in Appendix H.
6.1.3.3 Infiltration Rate - Soil Moisture Sensors
The infiltration wetting front generated as a result of spreading water within the pilot basin was
monitored using soil moisture sensors as described in Section 6.1.1.3 above. Recorded data were
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stored in and downloaded from a data logger located on the eastern basin berm. Soil moisture
sensor data are provided in Appendix F.
6.1.3.4 Ground Water Elevations
Ground water levels were measured in all monitoring wells at the Green Spot site prior to,
during, and after the pilot scale recharge basin was filled with water. Ground water levels were
measured between the time the wells were constructed and the time the recharge test started to
provide a baseline ground water level condition from which to compare ground water level
changes during the test. During the recharge test, ground water levels were measured to
document mounding associated with the recharge of surface water. After the recharge was
discontinued, ground water level monitoring was continued to measure the rate of decline in
water levels as the recharge water moved laterally in the subsurface. A summary of ground
water levels measured before, during, and after the recharge test are provided in Table 7.
Ground water levels were measured in well GS MW-1 (located in the center of the pilot recharge
test basin) using a dedicated pressure transducer installed in the well and set to collect readings
every 30 minutes. The data was downloaded to a laptop computer on a weekly basis. Ground
water levels were manually measured in all other area monitoring wells, including nearby well
20M (see Figure 16), using an electric water level sounder calibrated to the nearest 0.01 ft.
Ground water level measurements were recorded every other day prior to and during the
recharge test. Approximately one month after recharge stopped the measurement frequency was
reduced to approximately one per week. All depth to ground water measurements were
converted to ground water elevations (above mean sea level) by subtracting the depth to water
from the reference point elevation (see Table 7).
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6.1.4 Ground Water Quality Sampling and Analysis
Following pilot testing, ground water samples were collected from the monitoring wells in order
to assess changes to the condition of ground water quality in the area from artificially recharged
water. Prior to collecting ground water samples, each well was pumped until approximately
three casing volumes of water had been removed.
The ground water samples were collected from each well and submitted to E. S. Babcock &
Sons, Inc., a State of California certified laboratory, for water quality analysis. The samples
were collected in laboratory prepared bottles and stored on ice until delivered to the laboratory.
Chain-of-custody protocol was followed at all times during the collection, storage, and delivery
of the ground water samples. Immediately prior to sampling, the total dissolved solids (TDS),
pH, and temperature of the ground water was measured and recorded.
A summary of constituents analyzed are summarized in the Table 5. The results are summarized
in Table 6 and laboratory reports are contained in Appendix G.
6.1.5 Ground Water Tracer Testing
In consideration of California Department of Health Services regulations regarding the
subsurface residence time of recharge water for recycled water projects, the recharge water used
for the pilot recharge test was injected with an innocuous tracer to provide potential
supplemental information on the rate of ground water movement in the vicinity of the
Green Spot site.
Sulfur Hexafluoride (SF6) gas was chosen as the recharge water tracer for the following reasons:
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• It is conservative (does not stick to soil materials);
• It is harmless to humans (innocuous, very low concentrations needed for testing);
• Does not occur naturally; and
• Chemically non-reactive.
6.1.5.1 Method
For a period of 15 days (February 28 to March 13, 2004), a pressurized gas cylinder released
99.999% pure SF6 into the Green Spot site pilot spreading basin by diffusion through
semi-permeable silicon tubing. The tubing was placed at the bottom of the pilot spreading basin
and the SF6 release point was placed close to the vertical stand pipe in order to achieve optimal
mixing of SF6 with water within the pilot basin (see Figure 25). The injection rate was
maintained by using a pressure regulator set to approximately 5 pounds per square inch (PSI).
Injection of SF6 into the basin water was stopped three days prior to turning off the water inflow
to the basin. Therefore, it can be assumed that most, if not all, of the recharging water contained
dissolved SF6 gas.
During the injection period, pilot basin water samples were collected from a few centimeters
below the water surface in 15 milliliter (ml) BD Vacutainers™ every two days at nine designated
locations throughout the basin. These samples were collected to determine the SF6 tracer
concentration and spatial distribution within the pond so that its input function to the ground
water could be ascertained.
Concurrent to SF6 tracer injection, ground water samples were collected from the six monitoring
wells surrounding the pilot spreading basin. For the first month, ground water samples were
collected every other day. Following the first month of sampling, ground water was sampled on
a weekly basis from the Green Spot site monitoring wells and nearby active production wells
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(Lakewood Well Nos. 3, 5, 6, and 7; see Figure 12). All ground water samples collected for SF6
analysis were collected in 15 ml BD Vacutainers™.
All ground water samples collected for SF6 analysis were submitted to the University of
California, Santa Barbara (UCSB). Samples were analyzed with a gas chromatograph (GC)
using the method described by Clark et al., 2003. The GC detector response was calibrated
approximately every 10 samples with the following standards: approximately 148 parts per
trillion by volume (pptv), approximately 524 pptv, and approximately 1,947 pptv. The precision
and detection limits of this method were ±3% and 0.04 picomoles (pmol = 10-12 mol),
respectively. A summary of results from the tracer testing is provided in Table 8.
6.1.6 Climatological Data
Prior to the pilot testing, a temporary weather station was established on the eastern berm of the
pilot basin to record climatic data before, during, and after the pilot test (see Figure 26). The
weather station was equipped with a wind speed and direction sensor, ambient air temperature
thermometer, a barometer, a relative humidity gauge, and a rain gauge for recording precipitation
events. Data were continuously recorded, output to a data logger every 15 minutes, and
downloaded on a weekly basis using a laptop computer.
A standard United States National Weather Service Class A evaporation pan was installed on the
eastern berm of the pilot basin in accordance with guidelines presented by NOAA, 1989. The
pan measures 10 inches in depth and 47.5 inches in diameter, and was equipped with a stilling
well and hook gauge to record daily evaporation rates at the site.
A summary of data recorded by the weather station and from the evaporation pan are presented
in Appendix I.
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6.2 Van Dusen Canyon
6.2.1 Monitoring Wells
Five monitoring wells (VDC MW-1 to VDC MW-5) were drilled and installed at the Van Dusen
Canyon site from December 2003 through January 2004 (see Figure 18). With the exception of
VDC MW-1, pilot boreholes for the monitoring wells were drilled using a dual tube reverse
circulation drilling rig equipped with a 5 1/4-inch diameter bit. Each monitoring well pilot
borehole was later reamed to 12 1/4 inches diameter using the mud rotary drilling method. The
instrumented monitoring well (VDC MW-1) was completed within a 10 3/4-inch diameter
borehole drilled using the dual tube percussion hammer drilling method.
Soil samples were collected for classification during the drilling at each pilot borehole at 5-ft
intervals. Each sample was placed in 1 gallon sealable plastic bags which were properly labeled
in the field with the boring number, sample depth interval, and date of collection. Samples were
classified using the Unified Soil Classification System (USCS). Lithologic logs for the
monitoring well boreholes are provided in Appendix B.
At the completion of drilling, geophysical logs were performed in each borehole by Pacific
Surveys., Inc, of Claremont, California and are provided in Appendix D. Logs included the
following:
• 16 inch and 64 inch normal resistivity with point resistance;
• Spontaneous potential (SP);
• Focused guard resistivity (Laterolog);
• Acoustic (sonic); and
• Gamma ray.
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Due to the nature of the drilling method geophysical logs could not be performed in the
instrumented monitoring well borehole (VDC MW-1).
6.2.1.1 Casing and Screen
With the exception of VDC MW-1, monitoring wells were completed with 4-inch diameter
schedule 40 PVC blank and perforated well casing. The screened portion of each well casing
was perforated with 0.020-inch horizontal slots.
VDC MW-1 was constructed with 2-inch diameter schedule 40 PVC blank and perforated well
casing to a depth of 194 ft. The screened portion of the well casing, from 84 to 184 ft bgs, was
perforated with 0.02-inch horizontal slots.
Well completion details for each monitoring well are shown on Table 3 and in Appendix E.
6.2.1.2 Filter Pack and Annular Seals
The annular space between the borehole and wall and the well casing of each monitoring well,
with the exception of VDC MW-1, was filled with RMC Lonestar® #3 sand from the well bottom
to approximately 40 or 50 ft. The filter pack was placed in the annulus of all wells by pumping
through a tremie pipe using clear water as a circulating medium. With the exception of
VDC MW-1, all wells were completed with an annular seal, consisting of a sand cement slurry,
which was pumped through a tremie pipe from the top of the uppermost filter pack to the ground
surface.
The instrumented monitoring well (VDC MW-1) had RMC Lonestar® #3 sand installed within
the annular space from the bottom of the well at 194 ft bgs to 80 ft bgs, just above the perforated
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interval. RMC Lonestar® #30 sand was installed surrounding each soil moisture sensor,
approximately 3 ft above and 3 ft below, and a 4-ft bentonite seal was installed between each
(see Figure 27).
6.2.1.3 Soil Moisture Instrumentation
Watermark® soil moisture sensors (see Figure 20) were attached to the side of the 2-inch
diameter schedule 40 PVC casing at 10-ft intervals from 15 to 75 ft bgs (see Figure 27). The
annular space surrounding each sensor was filled with RMC Lonestar® #30 sand. A 4-ft
bentonite seal was placed between each sensor to ensure that basin water does not preferentially
migrate through the borehole. Soil moisture sensors were labeled as described in Section 6.1.1.3.
Each depth specific sensor was attached to a properly labeled port on an AM16/32 multiplexer.
The multiplexer was connected to a data logger (CR10X; see Figure 21) set to collect readings
every 10 minutes. Readings were stored within the data logger in units of kOhms (resistance)
and were downloaded at least weekly during testing.
Soil moisture data from the pilot recharge test are provided in Appendix F.
6.2.1.4 Surface Completions
All monitoring wells were completed with 8 5/8-inch OD steel monument-style protective well
covers with lockable lids. The protective well covers were cemented in place around the well,
leaving approximately 2 to 3 ft of stick up above the finished surface of the concrete well pad
(see Appendix E).
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6.2.1.5 Development
Each monitoring well was initially developed by bailing to remove any suspended material, then
by airlifting to remove colloidal and fine-grained sediments from within the well, filter pack, and
near well zone. Final development was conducted using a 2-inch diameter submersible pump.
Development continued until at least three well volumes of ground water had been discharged
from the well and when the turbidity was measured to be less than or equal to 5 nephelometric
turbidity units (NTU).
6.2.1.6 Ground Water Quality Sampling
Immediately following the well development process, ground water samples were collected from
each well and submitted to E. S. Babcock & Sons, Inc., a State of California certified laboratory,
for water quality analysis. The samples were collected in laboratory prepared bottles and stored
on ice until delivered to the laboratory. Chain-of-custody protocol was followed at all times
during the collection, storage, and delivery of the ground water samples. Immediately prior to
sampling, the total dissolved solids (TDS), pH, and temperature of the ground water was
measured and recorded.
Results were used to establish the baseline water quality condition of the ground water in the
area.
A summary of constituents analyzed are summarized in Table 5 (see Appendix G for laboratory
reports).
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