Aquifer Configuration TM Outline

Document Sample
Aquifer Configuration TM Outline Powered By Docstoc
					                     SPDSS Technical Memorandum
                                Final

To:            Ray Alvarado, CWCB
From:          Camp Dresser and McKee, Inc.
               Gordon McCurry, Andy Horn, Donavon Paschall and Mark McCluskey
Subject:       SPDSS Groundwater Component, Task 43.2 Phase 1
               Denver Basin Region Aquifer Property Technical Memorandum
Date:          July 30, 2004


Introduction

The groundwater component of Phase 1 of the South Platte Decision Support System
(SPDSS) focuses on compiling and evaluating available relevant data and creating a
groundwater database to support the Decision Support System (DSS) for the South
Platte River watershed. For the purposes of the SPDSS, the groundwater study area is
divided into two hydrologic regions based on the extent of the Denver Basin bedrock
aquifers (Figure 1). The Denver Basin Region includes the bedrock aquifers of the
Denver Basin and its overlying alluvium. The Denver Basin alluvial aquifer consists of
the alluvium of the South Platte River and its tributaries from just below Chatfield
Reservoir to Weldona. Included are the aquifers of Beebe Draw, Cherry Creek, Box
Elder Creek, Clear Creek, and other tributaries where they overlie the Denver Basin
bedrock aquifers. The mapped alluvial extent as shown in Figure 3 is an aggregate of
saturated alluvium and surficial geology as provided by Hurr and Schneider (1972a,
1972b, and 1973), Topper, et al. (2003), Smith, et al. (1964), Nelson, et al. (1967), Duke and
Longenbaugh (1966), Erker and Romero (1967), and Willard Owens Associates (1971). A
discussion of the Denver Basin aquifer nomenclature is provided in section 1.2.1. The
Lower South Platte Alluvium Region includes the unconsolidated alluvial deposits
located in the main stem of the South Platte River valley between Weldona and the
Nebraska State Line.

The current designation of the Denver Basin aquifers was established in 1985 with the
promulgation of the Denver Basin Rules, 2 CCR 402-6 (DWR 1985). The four principal
bedrock aquifers of the Denver Basin are, from bottom to top, the Laramie-Fox Hills, the
Arapahoe, the Denver and the Dawson. The Dawson and Arapahoe Aquifers have been
subdivided by the State Engineer‟s Office (SEO) into Upper and Lower units in the
northern portion of the basin based on the presence of lower permeability clay and shale
layers.

Of note is an area in the northwest corner of the Denver Basin Region referred to by the
SEO as the „complex area‟. This is a portion of the aquifer with extensive faulting and
vertical displacement in which the aquifer data should be viewed with some caution due
to the geologic activity.




                                              1
Overlying the Denver Basin is an alluvial aquifer, which consists of the alluvium of the
South Platte River and its tributaries. From a groundwater perspective, key tributaries
overlying the Denver Basin Region include East Plum Creek, Cherry Creek, Sand Creek,
Beebe Draw, Box Elder Creek, Lost Creek, Kiowa Creek, Bijou Creek, Upper Black
Squirrel Creek and Upper Big Sandy Creek, the last two of which are located in Water
Division 2 and drain into the Arkansas River.

The eastern and southern portions of the Denver Basin have been further subdivided into
several Designated Basins for the purposes of water rights administration. The
Designated Basins within the Denver Basin Region include the Lost Creek, Kiowa-Bijou,
Upper Black Squirrel and Upper Big Sandy.

This work was undertaken for the Colorado Water Conservation Board (CWCB), under
Tasks 32 and 43 of Phase 1 of the SPDSS by Camp Dresser & McKee (CDM). Tasks 32
and 43 of the SPDSS include the collection, analysis, and mapping of existing published
aquifer property data. The objectives of these tasks are as follows:

           1. Compile existing aquifer property information and create a HydroBase-
              compatible database with data from the Denver Basin and Lower South Platte
              Regions.
           2. Help identify additional data needs in these Regions.
           3. Support the design of the groundwater field program.
           4. Enhance HydroBase with aquifer property data collected during the Phase 1 field
              activities.

This Technical Memorandum was undertaken under Task 43.2, and summarizes the
compilation, analysis and mapping of existing published aquifer property data for the
Denver Basin Region.


Approach
The following table summarizes the sections contained in this technical memorandum
and identifies which section pertains to the objectives outlined above.


Section Description
1.0      Aquifer Properties Data Collection and Analysis. Describes the sources of
         existing data that were compiled to meet objective 1.
1.1      Sources of Data.
1.2      Data Analysis and Processing
2.0      Aquifer Properties Database. Describes how objectives 1 and 4 regarding
         HydroBase-compatible databases were met.
2.1      Database Structure
2.2      Database Quality Control
3.0      Results. Provides the results of the data analysis. Describes how objectives 2
         and 3 were met.



                                             2
3.1       Hydraulic Conductivity Data
3.2       Transmissivity Data
3.3       Specific Yield Data
3.4       Storativity Data


1.0 Aquifer Properties Data Collection and Analysis
Aquifer properties describe the potential for groundwater flow and the water-bearing
capacity of an aquifer. These aquifer properties include transmissivity, hydraulic
conductivity, storativity, and specific yield. The transmissivity (T) defines the flow
potential through a unit width of the entire saturated thickness of an aquifer under a
unit hydraulic gradient. Transmissivity measures the ability of the aquifer to transmit
groundwater throughout its entire saturated thickness. Typical units of measurement
are gallons/day/ft or ft2/day. The hydraulic conductivity (K) defines the flow potential
through a unit volume of an aquifer. It represents the aquifer transmissivity divided by
the aquifer saturated thickness. Typical units of measurement are ft/day. The
storativity (S) defines the amount of water that a unit volume of an aquifer can supply
per unit change in head. Storativity is unitless, and typical values for a confined aquifer
range from 10-3 to 10-5. The specific yield (Sy) defines the amount of water that a unit
volume of an unconfined aquifer can supply per unit change in head when drained
under the force of gravity. Specific yield is unitless, and typical values range from 0.05
for a clay to 0.25 for a coarse sand. The following section describes the approach used to
collect, analyze, and map historic aquifer property data for the Denver Basin Region.

1.1 Sources of Data
Aquifer property data relevant to the South Platte Decision Support System (SPDSS) in
the Denver Basin were gathered from a variety of published and non-published sources.
Published sources include data reports by the Colorado Water Conservation Board
(CWCB), the U.S. Geological Survey (USGS), and scientific journals and reports.
Unpublished data have been provided by the Centennial Water and Sanitation District
(CH2M Hill 1991), the South Metro Water Supply Study (Mulhern MRE 2003), the
SPDSS Phase 1 field investigations and through a review of SEO well permit data.

There are four categories of aquifer property data that are presented in this technical
memorandum which vary in their reliability and the level of supporting documentation.
The first category of aquifer property data are those derived from aquifer pumping tests,
in which water levels are monitored in one or more wells during a specific period of
pumping. These data are considered most reliable due to the nature of the testing and
detail with which data are collected during an aquifer pumping test. Significant sources
of aquifer property data derived from aquifer testing include Robson (1983), Hillier, et
al. (1978), Wilson (1965), CH2M Hill (1991), Smith, Schneider, and Petri (1964), Bjorklund
and Brown (1957), the South Metro Water Supply Study (Mulhern MRE 2003), and the
SPDSS Phase 1 field investigations.

The second category of aquifer property data is derived from well specific capacity tests
which are generally conducted after the installation of a pump. These tests are also
referred to as "pump tests" because the pump's ability to produce water from the well,


                                             3
rather than the aquifer's properties, is the subject of the test. These data are found in
McConaghy, et al. (1964), Schneider (1962) and, and the SEO well permit data and are
expressed in terms of pumping rate divided by drawdown.

A third category of aquifer property data is derived from laboratory testing of aquifer
materials. This method directly examines the physical properties of a sample of the
aquifer medium. Data of this type is often easier to collect than data from the previous
categories, but may be of more limited use due to:

      heterogeneity of the subject aquifer,
      weathering of a sample derived from an outcrop,
      degradation of the sample due to inadequate methods of collection, preservation,
       and analysis.

Geologic heterogeneity, such as that present in the Denver Basin aquifers, can result in a
discrete sample being unrepresentative of the aquifer's water-bearing characteristics.

Weathering of a sample after it has been collected can result in changes to the material's
composition and thus its ability to store and transmit water. For example, a sandstone
which is cemented with a soluble mineral such as calcite may, if collected from a natural
outcrop, have had the calcite cement removed by weathering. This would result in the
outcrop sample being more permeable than unweathered rock of the same formation.

Inadequate methods of collection, preservation, and analysis can result in changes in the
media which affect the analytical results. For example, a sample of sandstone obtained
from great depth could, upon removal to the surface, expand and fracture due to the
release of pressure. In addition, drying of the sample prior to analysis may cause
dessication of clay minerals resulting in an overestimation of hydraulic conductivity or
specific yield (Barkmann, 2003). In unconsolidated aquifers, the sampling process may
affect how representative the sample is of aquifer conditions through compaction or
loosening of the material by the sampling process.

Significant sources of aquifer property data derived from laboratory testing and located
within the Denver Basin Region include McConaghy, et al. (1964), Robson (1983), Major,
et al. (1983), Robson and Banta (1993), Lapey (2001) Barkmann (2001), and the SPDSS
Phase 1 field investigations. Not all sources report depth below ground surface from
which the sample was collected or if the sample was collected from an outcrop, and not
all sources report the methodology used to collect, preserve, and analyze the samples.

A fourth category of aquifer property data used in this report is contoured data for
which the underlying point values are not available. Contoured transmissivity data for
the South Platte Alluvium were obtained from the series of reports by Hurr and
Schneider (1972a - 1972d), which will be referred to herein simply as the Hurr and
Schneider reports. The Hurr and Schneider reports provide contoured transmissivity
data coverage of the mainstem alluvium of the South Platte River from downstream of
Denver, near Henderson, to the Colorado-Nebraska State Line. Hurr and Schneider
used approximately 1150 data points to construct the transmissivity contours of the


                                             4
alluvial aquifer over the entire mainstem, with a portion of these data being used to
develop the contours in the alluvial aquifer that overlies the Denver Basin Region.
However, the type of tests conducted, the method used to calculate transmissivity, and
the transmissivity point values used are not provided in the Hurr and Schneider reports.
Attempts to obtain the source data used in the Hurr and Schneider reports were
unsuccessful but as discussed in Section 3.1.1, comparison of point values obtained from
other sources to the contoured values presented in the Hurr and Schneider reports
shows a reasonable agreement. Therefore, it is believed that the data contained in the
Hurr and Schneider reports are valid to use without the raw data.

Robson (1983) also provides transmissivity and storativity contours for the four
principal Denver Basin aquifers. Robson (1983) consists of data from multi-well and
single well tests, and transmissivity values obtained from specific capacity testing.
Robson (1983) does not provide an accounting of how specific data points were
obtained.

Table 1 provides a summary of the total number of aquifer property data values that
were analyzed from a given report by aquifer. It is important to note that for one aquifer
test, specific capacity test or lab test, it is possible to obtain multiple aquifer property
data values. For example, from a single aquifer test, one could calculate a
Transmissivity, Hydraulic Conductivity, and Storativity Value. Table 1 indicates there
are a total of 1,611 aquifer property data values used in CDM‟s analyses and mapping,
which are included in HydroBase.

Table 1: Number of Aquifer Property Data Values by Source

                                                          Specific
                                     Aquifer Test         Capacity     Lab
     Source          Aquifer       T* K* S* Sy*             T*       K* Sy*   Total
 Bjorklund and
 Brown 1957       Alluvial          2    2        0   2      0       0   0      6
 CH2M Hill        Lower
 1991             Arapahoe          0    0        7   0      0       0   0      7
                  Laramie-Fox
                  Hills             1    1        7   0      0       0   0      9
 Halepaska &      Lower
 Assoc. 1997      Arapahoe          3    3        1   0      0       0   0      7
 Hillier 1978     Upper
                  Arapahoe          1    1        0   0      0       0   0      2
                  Lower
                  Arapahoe         17    17       1   0      0       0   0     35
 Lapey 2001       Lower Dawson     0     0        0   0      0       1   1     2
                  Denver           0     0        0   0      0       1   1     2
                  Lower
                  Arapahoe          0    0        0   0      0       1   1      2
                  Laramie-Fox
                  Hills             0    0        0   0      0       1   0      1



                                              5
                                                        Specific
                                   Aquifer Test         Capacity     Lab
    Source            Aquifer    T* K* S* Sy*             T*       K* Sy*    Total
Major, et al.     Lower
1983              Arapahoe       0    0        0   0       0       1    0     1
                  Laramie-Fox
                  Hills          0    0        0   0       0       7    0     7
McConaghy et      Alluvial       0    0        0   0      220      73   63   356
al. 1964          Upper Dawson   0    0        0   0       1       2    2     5
                  Lower Dawson   0    0        0   0       3       0    0     3
                  Denver         0    0        0   0       12      16   15   43
                  Upper
                  Arapahoe       0    0        0   0      18       3    3     24
                  Lower
                  Arapahoe       0    0        0   0       9       5    5     19
                  Laramie-Fox
                  Hills          0    0        0   0      24       7    6     37
Nelson, et al.
1967              Alluvial       5    5        0   0       0       0    0     10
Robson 1983**     Lower Dawson   0    16       0   0       0       5    5     26
                  Dawson
                  Undesignated   0    22       0   0       0       8    8     38
                  Denver         0    39       0   0       0       12   10    61
                  Lower
                  Arapahoe       0    70       0   0       0       10   6     86
                  Arapahoe
                  Undesignated   0    41       0   0       0       6    4     51
                  Laramie-Fox
                  Hills          0    78       0   0       0       23   23   124
Robson and
Banta GW          Lower
1990              Arapahoe       1    1        1   0      0        0    0     3
Schneider 1962    Alluvial       0    0        0   0      21       0    0     21
SEO Well
Permit
Database          Alluvial       0    0        0   0      166      0    0    166
Smith, et al.
1964              Alluvial       41   41       0   20      0       0    0    102
South Metro       Alluvial       1    1        0   0       0       0    0     2
Study             Lower Dawson   7    6        0   0       0       0    0    13
(Mulhern          Denver         24   22       0   0       0       0    0    46
2003)             Lower
                  Arapahoe       65   62       0   0       0       0    0    127
                  Laramie-Fox
                  Hills          37   35       0   0       0       0    0     72
SPDSS Phase
1 field studies   Alluvial       3    3        2   1                          9
                  Upper          1    1                            2          4



                                           6
                                                                    Specific
                                             Aquifer Test           Capacity        Lab
      Source             Aquifer           T* K* S* Sy*               T*          K* Sy*       Total
                     Arapahoe
 Wilson 1965         Alluvial              29     29       0   1         0         0     0       59
                     Upper
                     Arapahoe              1      1        0   0         0         0     0        2
                     Laramie-Fox
                     Hills                 9      9      2     0        0         0      0       20
 TOTALS:                                  248    506    21     24      474       185    153     1611
*T-Transmissivity (ft2/day), K- Hydraulic Conductivity (ft/day), S- Storativity (unitless), Sy- Specific Yield
(unitless)
**Some Robson (1983) aquifer test values were obtained from specific capacity data, however these are not
identified in the original report and so are defined herein as aquifer test data.



The following aquifer property data values were added to the database but are not
shown in any of the maps or included in Tables 1, 4, 5, 6, or 7: from Mulhern (2003), 64
aquifer property data values are believed to be calculated from aquifer tests performed
in wells that are completed in multiple aquifers; from Barkmann (2001), 10 vertical
hydraulic conductivity values are from lab tests of samples collected in the confining
layers of the Denver and Arapahoe Aquifers; from Major, et al. (1983), three values are
from lab tests of samples taken from the Laramie confining, one value is from a shale
unit in the Laramie-Fox Hills Aquifer, and one value is from a fractured core from the
Upper Arapahoe Aquifer; and from the SPDSS Phase 1 field investigation (Tasks 35.2
and 36.2), a vertical hydraulic conductivity value is calculated from a sample taken from
the confining unit between the Denver and Upper Arapahoe Aquifers, and another from
a confining unit within the Denver Aquifer.

1.2 Data Analysis and Processing
As described above, aquifer property data for the Denver Basin Region was compiled
from numerous sources. To create a database that is comprehensive, accurate, and
internally consistent, a variety of data analysis and processing steps were undertaken.
The remainder of this section describes those steps.

1.2.1 Denver Basin Bedrock Aquifer Nomenclature
The names of Denver Basin bedrock aquifers have changed over time. An
understanding of the nomenclature was needed to assign aquifer property data to the
correct aquifer based upon their current definitions.

The current designation of the Denver Basin bedrock aquifers was established in 1985
with the promulgation of the Denver Basin Rules, 2 CCR 402-6 (DWR 1985a). The four
principal aquifers of the Denver Basin are from bottom to top, the Laramie-Fox Hills, the
Arapahoe, the Denver and the Dawson. These aquifers are composed of interbedded
and discontinuous layers of sand, silt, and clay with some intervals containing gravel,
coal beds and/or volcanic rock fragments. The Arapahoe and the Dawson Aquifers are
further subdivided into upper and lower units over portions of their extents, resulting in


                                                       7
a total of six bedrock aquifers in the Denver Basin. The base of each aquifer is generally
defined by the presence of relatively thick sand-rich layers, as identified from borehole
geophysical logs.

The Denver Basin's early geologic studies, summarized by Romero (1976), have resulted
in inconsistent naming of the principal bedrock aquifers. In the late 19th century,
geologists applied the names Denver and Arapahoe to strata which nearly coincide with
the current designations (Emmons, et al. , 1896). From the early 1900‟s up until about
the mid-1970‟s, the three uppermost principal aquifers of Denver Basin were lumped
into one unit and were referred to as the Dawson Arkose with various subunits referred
to by lithology as lower, middle and upper conglomerate of the Dawson, etc. It was
during this era that many of the key reports that contain aquifer property data for the
region, including Smith, et al. (1964), Wilson (1965), Bjorkland and Brown (1957) and
Schneider (1962) were published. In the 1970s an examination of geophysical logs
indicated that the three uppermost aquifers could be mapped as units closely
corresponding to the early stratigraphic nomenclature, and the upper three aquifers
became known again as the Arapahoe, Denver, and Dawson (DWR 1985b). These
aquifers were mapped in the late 1970‟s and early 1980‟s, with the results provided in a
set of USGS reports (Robson, et al., 1981, Robson and Romero 1981a, Robson and
Romero 1981b, Robson 1983, Robson 1987, Robson 1996).

In 1985 the Denver Basin rules were established which further divided portions of the
Dawson and Arapahoe Aquifers into upper and lower units. The undivided portions of
each of these aquifers were assigned to the Upper Dawson and Upper Arapahoe
Aquifers, respectively. However, for the purposes of the SPDSS study, a physical
definition for the Dawson and Arapahoe is used where the data from the undivided
portions of these aquifers are assigned to the Lower aquifers. This was done so the data
from the Lower Dawson and Lower Arapahoe Aquifers would cover a larger physical
area than the data from their overlying Upper counterparts and would be more
consistent with the overall shape of the Denver Basin bedrock aquifers. However, this
physical definition is used in the SPDSS study for presentation purposes only and in no
way is meant to affect the legal definition of these aquifers.

1.2.2 Screened Data
Data were screened from the database for a variety of reasons:
     Wells and tests reported by multiple sources
     Data from wells that could not be assigned to a specific aquifer
     Tests that were reported by the published source with insufficient location or
        aquifer assignment information needed for analysis
     Wells located outside of the Denver Basin Region or outside an aquifer subcrop

For cases in which the same test was reported in two different sources, the value from
the source best representing the data was kept.

The history of the Denver Basin aquifers' nomenclature is significant because prior to the
mid-1970s, drillers commonly constructed wells in any coarse-grained lithologies
encountered, often screening through more than one of the Denver Basin aquifers.


                                             8
Aquifer property data from wells completed in multiple aquifers cannot be easily
applied to an individual aquifer according to their modern designations. Attempts to
develop a correlation of the pre-1970‟s nomenclature to the modern aquifer designations
have not been successful.

Data from aquifers defined using former aquifer nomenclature was evaluated to
determine whether if could be reassigned to the current aquifer designations. This was
possible for wells where the screened interval of the well and the well location was
provided in the original data report. An automated aquifer configuration interpolation
program informally referred to as the SB-5 program and associated database were
provided to CDM by the Office of the State Engineer. They were used to assign an
aquifer to a well for the older data that did not follow the aquifer designations of the
Denver Basin rules, promulgated in 1985 under Senate Bill 85-5 and informally referred
to as Senate Bill 5 or SB-5.

One of the functions of the SB-5 program is to provide the top and bottom elevations of
the Denver Basin aquifers based on the aquifer configuration defined in 1985. In order
to use the SB-5 program, it is necessary to know the well location and completion
interval. Many of the wells from the sources listed above did not provide this
information, and therefore the records were screened from the database because they
could not be assigned to a specific aquifer. Wells from McConaghy, et al. (1967) and
Wilson (1965) that were completed over multiple aquifers according to the SB-5 program
also were screened from the database. Eight of the wells from the South Metro Water
Supply Study (Mulhern MRE 2003) were screened over two aquifers. These data were
retained in HydroBase but not shown in Table 1 nor displayed on the aquifer property
maps because they likely represent averaged data from multiple aquifers.

Robson (1983) provides the most comprehensive dataset for the Denver Basin aquifers,
accounting for almost half of the aquifer test data and 40 percent of the laboratory-based
test results analyzed for the Denver Basin Region (Table 4). The Robson 1983 study,
however, did not distinguish between the upper and lower portions of the Dawson and
Arapahoe Aquifers within their respective divided zones. Well completion information
is not available for the data contained in Robson (1983), and therefore the SEO‟s SB-5
program, described above, could not be used to assign data points to the Upper or
Lower Dawson and Arapahoe Aquifers in their respective divided portions. Rather than
screen these points from the database because they could not be assigned to an aquifer
as defined by the Denver Basin Rules (DWR 1985a), these points were defined as
Arapahoe "undesignated" or Dawson “undesignated.” For the purposes of the SPDSS
study, these data were posted on both the Upper and Lower Dawson and the Upper and
Lower Arapahoe Aquifer maps. The Robson (1983) data from these aquifer is shown in
a grey scale to distinguish it from data known to be from these divided aquifer layers.
As shown on the figures for these aquifer layers, the Robson (1983) data makes up the
majority of the data values shown and, generally, is similar to other posted values from
the Upper and Lower units of an aquifer. Until other data become available it is felt that
the Robson (1983) data are a reasonable representation of the hydraulic conductivity
distributions for these aquifers. For the purpose of the SPDSS, all non-laboratory data
obtained from Robson (1983) are considered as "aquifer test" data regardless of whether


                                            9
the data were obtained from specific capacity or aquifer tests since the method or source
of the data were not identified in the original report.

To remove redundant data, GIS spatial queries were performed between several source
datasets that were considered to have reported the same aquifer test data. If a data point
was located within approximately 500 feet of a data point from another source it was
screened. Data screening based on redundancy are identified in Tables 2 and 3 for the
Denver Basin Region bedrock and alluvial aquifers, respectively.

Table 2 summarizes screened aquifer property tests from the Denver Basin bedrock
aquifers, and consists of 253 tests screened for the reasons indicated in the table. Table 3
summarizes screened aquifer property tests from the Denver Basin alluvial aquifer and
consists of 173 tests screened for the reasons indicated. Table 4 summarizes the total
number of aquifer property tests screened and the total number analyzed for each
source. It should be noted that Tables 2-4 refer to aquifer tests while Table 1 refers to
individual data points. In some cases a single test will provide data points of several
types (T, K, Sy, etc) and/or from multiple depth intervals from a given location and so
the numbers in Table 1 will be higher for a given data source than as reported in Tables
2-4.


Table 2: Screened Aquifer Property Tests - Denver Basin Bedrock Aquifers
                                                             Well
                                                             located
               Unable                              Test      outside
               to       Well                       Reported Denver Test
               Assign Completed Insufficient in              Basin or Performed
               Well to in Multiple Data            Another Aquifer in Coal
 Data Source Aquifer Aquifers        Reported      Source    Subcrop Mine                      Total
 McConaghy,
 et al. (1964)    52         49             8                   15                             124
 Wilson
 (1965)           9           3             3                    2         1                    18
 Robson
 (1983)                                                70        3                              73
 Lapey (2001)                                          8                                         8
 Hill (1991)                                           30                                       30
 Total            61         52            11         108       20         1                   253




                                             10
Table 3: Screened Aquifer Property Tests- Denver Basin Alluvial Aquifer
                                                                                                Well
                                                                                                located
                                                                                                outside
                                      Well Completed                         Test               Denver
                                      in the Alluvium           Insufficient Reported in        Basin or
                                      and Underlying            Data         Another            Aquifer
 Data Source                          Bedrock                   Reported     Source             Subcrop    Total
 McConaghy, et al. (1964)                    14                     16             20                        50
 Wilson (1965)                                                      11             39               25       75
 Schneider (1962)                                                    6             39                        45
 Nelson, et al. (1967)                                                              3                        3
                       Total                   14                   33            101               25      173




Table 4: Number of Aquifer Property Tests by Source
                                       Total                                                Total
                                     Aquifer                        Total                   Number of
                                       Tests         Total         Specific     Total       Aquifer
                                     Screened       Aquifer        Capacity      Lab        Property
                                       from          Tests          Tests       Tests       Tests
Data Source                          Analysis       Analyzed       Analyzed    Analyzed     Analyzed
Bjorklund and Brown (1957)                              2              0          0               2
CH2M Hill (1991)                         30            14              0          0              14
Halepaska & Assoc. (1997)                               3              0          0               3
Hillier, et. al. (1978)                                18              0          0              18
Lapey (2001)                             8              0              0          4               4
Major (1983)                                            0              0          8               8
McConaghy, et al. (1964)                174             0            287         110            397
Nelson , et al. (1967)                    3             5              0          0               5
Robson (1983)                            73           266*             0          86            352
Robson and Banta (1990)                                 1              0          0               1
Schneider (1962)                         45             0             21          0              21
Smith, et al. (1964)                                   41              0          0              41
SEO Well Permit Database                                             166                        166
South Metro Water Supply
Study (Mulhern MRE 2003)                                 134           0           0              134
SPDSS Field Study                                          4                       3               7
Wilson (1965)                            93               39           0           0               39
Totals:                                 413              527*         474         211            1212
*Some Robson (1983) aquifer test values were obtained from specific capacity data, however these are not
identified in the original report and so are defined herein as aquifer test data.




                                                    11
1.2.3 Estimation of Transmissivity Based on Specific Capacity Tests
A large percentage of the Denver Basin aquifer property data obtained during Phase 1
has been derived from aquifer specific capacity tests. This category of data required
more analysis and processing than other categories of data, as described in this section.

Specific capacity tests are often referred to as "pump tests" because they test the pump's
ability to produce water from the well. However, many have found that specific
capacity tests can be used to estimate an aquifer‟s transmissivity (Fetter 2001, Razak and
Huntley 1991, Robson 1983, Driscoll 1986, Hurr 1966, Smith, et al. 1964). Analyses of
specific capacity tests are typically performed by developing an empirical relationship
between the transmissivity values obtained from aquifer tests conducted in the area and
the corresponding specific capacity data. The relationship is then applied to wells for
which specific capacity data exist but no aquifer test data exist to estimate a
transmissivity for a given location. For confined aquifers, transmissivity can also be
estimated from specific capacity for confined aquifers by using a modification of the
Theis equation (Fetter 2001). Significant sources of Denver Basin aquifer property data
derived from specific capacity testing include McConaghy, et al. (1964), and Schneider
(1962).

For data located in the unconfined alluvial aquifers, a linear regression equation was
developed to relate specific capacity and transmissivity values derived from the same
aquifer test. The data used were from unconfined alluvial aquifers of the South Platte
River and its tributaries from Denver downstream to Julesburg, thus covering both the
Denver Basin and Lower South Platte Alluvium Regions. Sources for the data where
both types of test data existed at a given location were Wilson (1965), Smith, et al. (1964),
and Nelson, et al. (1967), for a total of 77 data pairs. The Wilson (1965) report includes
data from the Lower South Platte Alluvium Region that is not included in Table 1 since
these data are presented in the Task 43.3 Technical Memorandum. The Wilson (1965)
data are reported as being 24-hour duration specific capacity values. The specific
capacity tests from Smith, et al. (1964) and Nelson, et al. (1967) were of varied duration
but lasting two hours or greater.

Use of specific capacity data has limitations caused by the rapid drawdown of a well in
the early stage of being pumped, before near-equilibrium conditions are reached. To
minimize the possibility of bias from rapid drawdown in the early stages of pumping,
only tests conducted for two hours or more were considered for analysis. This screening
criterion resulted in 456 of the approximately 2,500 well records in McConaghy, et al.
(1964) and 63 of the approximately 1,500 well records in Schneider (1962) being used for
further analysis. Specific capacity data points from tests lasting less than two hours
from the above-mentioned sources are not considered in further discussion of data
analysis and screening.

Transmissivity is affected by changes in water levels. An analysis of water levels for the
Denver Basin Region alluvium conducted under Task 44 indicates that, generally,
aquifer water levels have changed little in most areas since the 1960‟s. Therefore,
transmissivity (T) values computed from specific capacity data collected at different
times can in this case be combined into a single database with little error.


                                             12
The linear trend of specific capacity versus aquifer test-derived transmissivity suggests
there is no need to differentiate between tests performed in the South Platte mainstem
alluvial aquifer and its tributaries. A relationship was developed between T and specific
capacity using linear regression techniques. An initial linear regression, with a straight-
line fit forced through the origin, applied to the data and an equation for these data of T
= 1.7813 x specific capacity resulted from using all of the data, with an R-squared value
of 0.6337. The R-squared value indicates how closely the data fits the trend line with an
R-squared value of 1 representing a perfect correlation of the data. A total of seven data
points from the full dataset were felt to be outliers, because on further review these data
were found to be inconsistent with other aquifer test results from nearby locations.
These outliers were therefore not used to develop a final relationship between specific
capacity and transmissivity. A straight-line fit forced through the origin was applied
again to the data. The derived equation of the line was (all units in ft2/day):

                        Transmissivity = 1.9606 x Specific Capacity

The R-squared of this linear regression line was 0.8733, a very good fit considering the
varying locations, test duration, and sources of data. The specific capacity data and line
fit are shown in Figure 2a. This linear regression equation was then used to calculate
transmissivity values for the much larger dataset consisting of the alluvial aquifer
specific capacity tests reported in the SEO Well Permit database, McConaghy, et al.
(1964) and Schneider (1962). The calculated T values are consistent with the pumping
test point values and with the contoured values presented by Hurr and Schneider
(1972a-c), showing validity to the method.

For the bedrock aquifers specific capacity tests values aquifers reported in McConaghy,
et al. (1964) were converted to a transmissivity value using Jacob‟s modification of the
Theis equation (Fetter 2001). This is a different approach than taken for the alluvial
aquifer data since there are fewer bedrock data upon which to develop a linear
relationship, because the Theis equation was developed for confined aquifers and so is
appropriate for use in this application, and because this equation allows for site-specific
information to be used. The Jacob modification to the Theis equation is given as:

     Q   2.3        2.25  T  time
T           log(                 )
     s 4              r2  S

Where:

Q = Well discharge rate (ft3 / day)
s = drawdown in well
T = aquifer transmissivity (ft2 /day)
time = duration of pumping
S = storativity

This method requires estimates or assumptions for the storativity, well efficiency and
effective hydraulic radius of the well. In this analysis, a storativity value of 0.0001 was


                                             13
assumed for all bedrock tests. This value is in the range expected for confined bedrock
aquifers in the Denver basin based on estimates by Robson (1983). All wells were
assumed to be 100 percent efficient and have an effective hydraulic radius equal to the
radius of the casing reported for the well. With these assumptions made, the equation
was solved iteratively for transmissivity. Due to differences in specific capacity test
duration, aquifer thickness and well efficiency, use of the theoretical approach provides
more flexibility for the bedrock aquifers. The validation of this method used 30 aquifer
tests where both a specific capacity at a known time and an aquifer test derived
transmissivity were available in the database.

The transmissivity results estimated from the Theis equation were compared to the
aquifer test-derived values. Figure 2b shows this comparison, along with the regression
line relating the transmissivity estimates from the two methods. The R-squared value
relating the two sets of data is 0.763, a reasonable correlation. As can be seen, the
specific capacity-based estimates are biased high by about 10 percent, compared to the
aquifer test based estimates. This is likely due to the assumption that wells are 100
percent efficient in the specific capacity analysis. Most wells are closer to 80 percent
efficient, which would lower the specific capacity estimates and provide a better
regression fit. However, since the efficiency of the individual wells used in the analysis
is not known there were no further attempts to refine the analysis at this time.

1.2.4 Hurr and Schneider Transmissivity Contours
The Hurr and Schneider reports (1972a-c) include contoured transmissivity data for the
alluvial aquifer in the mainstem of the South Platte River in the Denver Basin Region
downstream of Denver. Values for individual data points are not presented in Hurr and
Schneider (1972a-c). These data were presented originally in units of thousands of
gal/day/ft. The contour units were converted to ft2/day to maintain consistent units
with other data reported in this Technical Memorandum. The contours were
transformed into point values using GIS. The point data were gridded in Surfer® in
units of ft2/day and contoured with an interval of 10,000 ft2/day. The recontoured
transmissivity data were visually compared to Hurr and Schneider‟s (1972a-c) original
contours to assess the accuracy of the new contours. It was determined that the new
contours, in ft2/day units, matched the original Hurr and Schneider contours.


2.0 Aquifer Properties Database
This section describes the procedures used to catalogue and compile all the data sources
into the appropriate HydroBase formats.

2.1 Database Structure
CDM used a HydroBase database template developed by the SEO as the basis for the
SPDSS groundwater database. Appendix A provides a summary of the tables, fields,
and data sources used in the database.

Five data tables contain aquifer property data for the Lower South Platte Alluvium
Region. These are called the WELL, WELL_DATA_SOURCE, PUMP_TEST,
REF_ELEV_ACCURACY and REF_LOC_ACCURACY.


                                            14
The WELL table contains the location, well elevation, permit number, well depth, and
many other types of information about wells in the SPDSS study area. The WELL table
is the core table in the SPDSS database and links well information data with geophysical
log, water level, aquifer test, and GIS data gathered by CDM. This table was populated
with data gathered by CDM with the addition of the following fields:
      spdss_region
      elev_accuracy_num
      well_owner

The elev_accuracy_num field is a numeric value that identifies the accuracy of the
elevation of the data point based on the source of the data.

The WELL_DATA_SOURCE table of HydroBase contains the fields well_id, data_source
and identifier. This table is used to link the HydroBase well_id with the original source
well identifier.

The core of the aquifer properties data, both field data and lab data, is stored in the
PUMP_TEST table. No new fields were added to this table

The REF_LOC_ACCURACY table includes comments on the horizontal siting accuracy
of the location (X,Y) data. A new value was added to the REF_LOC_ACCURACY table
called „original‟. This value indicates that the source of the XY location was provided in
the original database.

A new reference table was added and called REF_ELEV_ACCURACY. This table is
similar to the REF_LOC_ACCURACY table and qualifies the source and accuracy of the
elevation value. The values in the table currently include: „original‟, „USGS DEM‟ and
„surveyed‟.

All of the aquifer property data was combined and placed in the appropriate tables.
Each data point was given a unique identification (well_id) that was used to track the
source of the data. For example, aquifer configuration (AC) data obtained from the State
Engineer geophysical logs database has a CDM_ID of AC_SEO_# to indicate that it was
originally obtained from that report. Quality control procedures used to verify accuracy
in data transfer are discussed in the following section.

2.2 Database Quality Control
Numerical data from each of the sources were initially entered into a Microsoft Excel®
spreadsheet. The data were then checked for accuracy by comparing 100 percent of the
entered data to the original hard copy data. If errors in the data entry were found, the
error was corrected in the spreadsheet. The spreadsheet was then uploaded into the
HydroBase-compatible database. This procedure was used to assure quality for all data
that was added to the Denver Basin Region Aquifer Property database.

Published contour and point data from the Hurr and Schneider (1972) reports, Robson
(1983), and Hillier, et. al. (1978) were scanned to a graphic image file and then digitized


                                             15
and assigned a contour or point value. The digitized contour and point values were
then assessed for quality and accuracy by the following procedure. The digitized
contours and points were overlain on the graphic image of the original contour or point
map. One hundred percent of the digitized contours and points were verified for the
appropriate contour interval and value or point value by comparison with the contour
or point data graphic image.

3.0 Results
The properties of each aquifer are discussed briefly below. The property data collected
from aquifer (field) tests is reported separately from lab test data because these methods
of data collection differ significantly, as discussed in Section 1.1. Summary data for the
number, range and median values are provided in Tables 5 through 8 for hydraulic
conductivity, transmissivity, specific yield and storativity, respectively, for each aquifer.
The transmissivity summary (Table 6) includes results from both aquifer tests and
specific capacity tests. Median values are presented in the tables and the following
discussion, because most of the aquifer parameter data have a log-normal distribution of
sample values. In cases where data have this population distribution, the median value
rather than the mean value best represents the average of the particular dataset. The
purpose of describing the data by the median value is to allow the characteristics of each
aquifer to be compared in a relatively straightforward manner.


Table 5 Summary of Hydraulic Conductivity Data (ft/d)
                                                                                                 Figure
                               Aquifer Test                           Lab Test                  Number
 Aquifer              Count    Min Max Median Count                Min     Max     Median
 Alluvial              81      18.0 2005    401 73                 0.008 3877       92.2           3
 Upper Dawson           0       0      0         2                  6.15   8.69     7.4            4
 Lower Dawson          22      0.01   4.6   0.5  6                  0.01    4       0.4            5
 Dawson
 Undesignated           22      0.1     6.2        1.0      8       0.02     11      1.0           5
 Denver                 61      0.03    24         0.5     29     9E-05     989      0.1           6
 Upper Arapahoe          3      2.1    4.01        4.0      5      0.005    4.95     0.59          7
 Lower Arapahoe        153      0.1     10         2.3     17     0.0003    8.96     0.4           8
 Arapahoe
 Undesignated           41      0.06    4.7        1.2      6       0.6      6       4.7           8
 Laramie-Fox
 Hills                 123     0.003    7.2        0.4     38     0.0004    70       0.52          9




                                              16
Table 6 Summary of Transmissivity Data (ft2/d)
                         Aquifer And Specific Capacity Tests                                   Figure
 Aquifer                 Count     Min          Max     Median                                Number
 Alluvial                 488        56        679,395  12,032                                10a,b,c
 Upper Dawson               1       348          348      348                                    11
 Lower Dawson              10        42          562      285                                    12
 Denver                    36         8          588      96                                     13
 Upper Arapahoe            21        11          503      120                                    14
 Lower Arapahoe            95        18         3,100    1,025                                   15
 Laramie-Fox Hills         71         3          812      62                                     16


Table 7 Summary of Specific Yield Data (decimal percent)
                                                                                                              Figure
                                       Lab Test            Aquifer Test                                       Number
 Aquifer                 Count       Min Max Median Count Min    Max Median
 Alluvial*                63         0.096 0.37 0.27 26   0.0008 0.21   0.06                                    17
 Upper Dawson              2         0.245 0.34 0.29  0      0     0                                            18
 Lower Dawson              6         0.069 0.24 0.17  0      0     0                                            19
 Dawson
 Undesignated                8       0.036    0.27         0.14       0         0         0                     19
 Denver                     26       0.002    0.46         0.14       0         0         0                     20
 Upper Arapahoe              3       0.033    0.27         0.25       0         0         0                     21
 Lower Arapahoe             12       0.056    0.40         0.16       0         0         0                     22
 Arapahoe
 Undesignated                4       0.142    0.27         0.21       0         0         0                     22
 Laramie-Fox
 Hills                      29       0.048 0.38           0.21          0         0        0                    23
*Some of the aquifer test specific yield values reflect the storativity of semi-confined aquifer conditions
or are biased by the effects of delayed gravity drainage



Table 8 Summary of Storativity Data (decimal percent)
                                                                                     Figure
                                               Aquifer Test                          Number
 Aquifer                         Count     Min       Max                  Median
 Upper Dawson*                     0         0         0                                      24
 Lower Dawson*                     0         0         0                                      25
 Denver*                           0         0         0                                      26
 Upper Arapahoe*                   0         0         0                                      27
 Lower Arapahoe                   10     2.48E-05    0.008                0.00024             28
 Laramie-Fox Hills                 9     0.00002     0.004                0.00076             29
*No point data is available for these aquifers, but the figures show Storativity contours from Robson
(1983).




                                                     17
3.1.1 Denver Basin Alluvial Aquifer Property Data
A total of 81 aquifer test and 73 laboratory hydraulic conductivity values were obtained
for the Denver Basin alluvial aquifers. The median values are 401 and 92 ft/d,
respectively. The laboratory test values are significantly lower than the aquifer test
values in the alluvium, possibly due to sample collection, preservation, and analysis
methods as discussed in Section 1.1. The median transmissivity value of 488 aquifer
tests is 12,032 ft2/d.

The median specific yield values obtained from 26 aquifer and 63 laboratory tests were
0.06 and 0.27, respectively. The reasons for the lower than expected specific yield values
resulting from aquifer testing in the alluvium are discussed in Smith, et al. (1964), the
source of most of the values. Reasons for the low values are attributed to effects of test
bias resulting from aquifer heterogeneity, short duration of most tests, and recharge of
produced water at most locations tested. An additional bias is the effect of delayed
gravity drainage, as discussed in Boulton (1963). Electronductivity logs from the SPDSS
Phase 1 field investigations, as discussed in the Task 35.2 Technical Memorandum, show
that some of the Phase 1 aquifer tests were conducted in semi-confined aquifer
conditions and thus the values are more reflective of storativity than specific yield.

Maps presenting the data locations and values of the properties for this aquifer are
presented as Figures 3, 10, and 17. In some locations such as shown on Figure 3,
multiple values are presented for a given data point; these represent laboratory test
results from multiple core samples from the same boring. Tables 5 through 8 summarize
the data discussed above.

3.1.2 Upper Dawson Aquifer Property Data
Two laboratory test hydraulic conductivity values, with a median value of 7.4 ft/d, were
obtained from the Upper Dawson Aquifer. One transmissivity value of 348 ft2/d was
obtained. Two specific yield values obtained from laboratory testing have a median
value of 0.29. For comparison, Senate Bill 5 assigned a specific yield value of 0.20 for the
Dawson Aquifer. No aquifer pumping test-derived transmissivity, hydraulic
conductivity, specific yield or storativity values are currently available which can be
designated to this aquifer.

Maps presenting the data locations and values of the properties for this aquifer are
presented as Figures 4, 11, 18 and 24. Tables 5 through 8 summarize the data discussed
above.

3.1.3 Lower Dawson Aquifer Property Data
A total of 22 aquifer test hydraulic conductivity and six laboratory values, with median
values of 0.5 and 0.4 ft/d, respectively, were obtained from the Lower Dawson Aquifer.
The median transmissivity value of 10 tests is 285 ft2/d. The median specific yield value
obtained from six laboratory tests is 0.17. No aquifer pumping test-derived specific
yield or storativity values are currently available which can be assigned to this aquifer.




                                            18
Maps presenting the data locations and values of the properties for this aquifer are
presented as Figures 5, 12, 19 and 25. For the purposes of mapping, the Lower Dawson
dataset also includes data from the undivided portion of the Dawson Aquifer, as
discussed in Section 1.2.1. Tables 5 through 8 summarize the data discussed above.

3.1.4 Undesignated Dawson Aquifer Property Data
As discussed in Section 1.2.1, data from the Robson (1983) data source that are located in
the divided portion of the Dawson Aquifer are referred to in this report as Undesignated
Dawson Aquifer data since it was not possible from the information provided to assign
the data to the Upper or Lower aquifer layer. A total of 22 aquifer test and eight
laboratory hydraulic conductivity data points, both with median values of 1.0 ft/d,
respectively, were obtained for this dataset. The median specific yield value obtained
from eight laboratory tests is 0.14. No storativity or transmissivity values are currently
available.

The data locations and values for these data could not be assigned to either the Upper or
Lower Dawson Aquifer and so are presented as grayscale data points on both the Upper
and Lower Dawson Aquifer figures referenced above to distinguish them from other
data that could be assigned to the Upper or Lower unit. In addition, the figure or table
number from the original source are cited in the Legend on each figure because so many
of the data are from the Robson (1983) source. Tables 5 through 8 summarize the data
discussed above.

3.1.5 Denver Aquifer Property Data
A total of 61 aquifer test and 29 laboratory hydraulic conductivity data points, with
median values of 0.5 and 0.1 ft/d, respectively, were obtained for this aquifer. The
median transmissivity value of 36 tests is 96 ft2/d. The median specific yield value
obtained from 26 laboratory tests is 0.14. For comparison, Senate Bill 5 assigned a
specific yield value of 0.17 for the Denver Aquifer. No aquifer pumping test-derived
specific yield or storativity values are currently available which can be assigned to this
aquifer.

Maps presenting the data locations and values of the properties for this aquifer are
presented as Figures 6, 13, 20 and 26. Tables 5 through 8 summarize the data discussed
above.

3.1.6 Upper Arapahoe Aquifer Property Data
A total of 3 aquifer test and 5 laboratory hydraulic conductivity data points, with
computed median values of 4.0 and 0.59 ft/d respectively, were obtained for this
aquifer. The median transmissivity value of 21 tests is 120 ft2/d. The median specific
yield value obtained from three laboratory tests is 0.25. For comparison, Senate Bill 5
assigned a specific yield value of 0.17 for the Arapahoe Aquifer. No aquifer pumping
test-derived specific yield or storativity values are currently available which can be
assigned to this aquifer.




                                             19
Maps presenting the data locations and values of the properties for this aquifer are
presented as Figures 7, 14, 21 and 27. Tables 5 through 8 summarize the data discussed
above.

3.1.7 Lower Arapahoe Aquifer Property Data
A total of 153 aquifer test and 17 laboratory hydraulic conductivity data points, with
median values of 2.3 and 0.4 ft/d, respectively, were obtained from this aquifer.
Possible reasons for the general disagreement between laboratory and aquifer tests are
discussed in Section 1.1. The median transmissivity value of 95 tests is 1,025 ft2/d. The
median specific yield value obtained from 12 laboratory tests is 0.16. A total of ten
storativity values were obtained from the confined portions of the aquifer with a median
of 0.00024.

Maps presenting the data locations and values of the properties for this aquifer are
presented as Figures 8, 15, 22 and 28. For the purposes of mapping, the Lower
Arapahoe dataset also includes data from the undivided portion of the Arapahoe
aquifer, as discussed in Section 1.2.1. Tables 5 through 8 summarize the data discussed
above.

3.1.8 Undesignated Arapahoe Aquifer Property Data
As discussed in Section 1.2.1, data from the Robson (1983) data source that are located in
the divided portion of the Arapahoe Aquifer are referred to in this report as
Undesignated Arapahoe Aquifer data since it was not possible from the information
provided to assign the data to the Upper or Lower aquifer layer. A total of 41 aquifer
test and six laboratory hydraulic conductivity data points, with median values of 1.2 and
4.7 ft/d, respectively, were obtained. The median specific yield value obtained from
four laboratory tests is 0.21. No storativity or transmissivity values are currently
available.

The data locations and values for these data could not be assigned to either the Upper or
Lower Arapahoe Aquifer and so are presented as grayscale data points on both the
Upper and Lower Arapahoe Aquifer figures referenced above to distinguish them from
other data that could be assigned to the Upper or Lower unit. In addition, the figure or
table number from the original source are cited in the Legend on each figure because so
many of the data are from the Robson (1983) source. Tables 54 through 8 summarize the
data discussed above.

3.1.9 Laramie-Fox Hills Aquifer Property Data
A total of 123 aquifer test and 38 laboratory hydraulic conductivity data points, with
median values of 0.4 and 0.5 ft/d, respectively, were obtained for this aquifer. The
median transmissivity value of 71 tests is 62 ft2/d. The median specific yield value
obtained from 29 laboratory tests is 0.21. For comparison, Senate Bill 5 assigned a
specific yield value of 0.15 for the Laramie-Fox Hills Aquifer. A total of nine storativity
values were obtained from the confined portions of the aquifer with a median of 0.00076.

Maps presenting the data locations and values of the properties for this aquifer are
presented as Figures 9, 16, 23 and 29. Of note on these Figures is an area in the


                                            20
northwest edge of this aquifer labeled the „complex area‟. This is a portion of the aquifer
with extensive faulting and vertical displacement in which the aquifer data should be
viewed with some caution due to the geologic activity. Tables 5 through 8 summarize
the data discussed above.


Summary and Conclusions
CDM completed SPDSS Tasks 32 and 43, Phase 1 collection, analysis, and mapping of
aquifer property data for the Denver Basin Region. This technical memorandum
examines the sources and types of available data, presents the tables and formats in
which the data are stored in HydroBase, and presents the data in a spatial format. The
data were used to help identify additional data needs in the Denver Basin Region and to
support the design of the groundwater field data collection program. Below are
conclusions from completion of these Phase 1 tasks.

   The Phase 1 Task 32, 43.1 and 43.2 activities satisfied the Phase 1 objectives of
    collecting available published aquifer Property data, enhancing HydroBase with
    these data, guiding the Phase 1 field investigations, and helping characterize the
    hydraulic properties of the alluvial and bedrock aquifers in the Denver Basin Region.

   The aquifer property data that have been collected, analyzed and presented in this
    Technical Memorandum represents a significant contribution to the knowledge and
    characterization of the groundwater system within the Denver Basin Region.
    Aquifer property data from 16 sources were combined, converted to consistent
    reporting units and are being presented for the first time in many cases in graphical
    format and in a readily available report and database via Task 43.2 of the SPDSS
    project.

   The Phase 1 SPDSS field investigations (Tasks 35.1 and 36.1) provided additional
    aquifer property data in portions of the alluvial aquifer and Upper Arapahoe
    Aquifer where little or no data previously existed. These data helped to fill in the
    Phase 1 aquifer property data gaps for this Region.

   The aquifer transmissivity and hydraulic conductivity data for the alluvial aquifers
    within the Denver Basin Region as presented in this Technical Memorandum
    appears to be sufficient for the purposes of commencing regional-scale water
    resources planning and groundwater modeling. However, on a local scale,
    additional data would be beneficial to refine the existing characterization of these
    alluvial aquifer properties.

   The aquifer transmissivity and hydraulic conductivity data for the bedrock aquifers
    within the Denver Basin Region as presented in this Technical Memorandum does
    not appear to be sufficient in many areas for conducting further water resources
    planning assessments.




                                            21
   The aquifer storage coefficient data in the alluvial aquifers overlying the Denver
    Basin Region as presented in this Technical Memorandum appears to be sufficient
    for conducting further water resources planning assessments in the area along the
    mainstem of the South Platte River upstream of the Kersey area east of Greeley, but
    does not appear to be sufficient in the mainstem areas downstream of Greeley, nor in
    the tributary alluvial aquifers overlying the Denver Basin bedrock aquifers.
    However, three additional aquifer tests and additional analyses are planned in Phase
    2 for the alluvium which will help fill these data gaps.

   The aquifer storage coefficient data in the bedrock aquifers in the Denver Basin
    Region as presented in this Technical Memorandum do not appear to be sufficient
    for conducting further water resources planning assessments.

   Aquifer transmissivity information in the alluvial aquifer along the mainstem of the
    South Platte River appears to be well characterized from the contoured maps
    presented by Hurr and Schneider and compare well with point values when
    considered on a regional basis.

   The most comprehensive data source available during Phase 1, Robson (1983), does
    not differentiate data between the divided portions of the Upper and Lower
    Arapahoe and Dawson Aquifers. However, the data for each of these aquifers from
    all data sources does not appear to differ appreciably between the Upper and Lower
    units of each aquifer so it is a valuable data set to retain and use for these aquifers
    until other aquifer-specific data become available.

   There is a high concentration of aquifer property data for the Denver Basin aquifers
    near the Denver Metropolitan area, but many other portions of the 6,700 square mile
    basin are lacking in data. The lack of spatially-distributed data may be a concern for
    future aquifer assessment, characterization, and modeling efforts.

   The aquifer property maps presented in this Technical Memorandum were used in
    conjunction with the figures produced in the other Technical Memoranda (Tasks 42.2
    and 44.2) to support the design of the Phase 1 groundwater field data collection
    program (Task 33).

   The aquifer properties database was incorporated into HydroBase. Several minor
    additions were made to the existing HydroBase tables in collaboration with the State,
    as discussed in Section 2.1, to provide additional relevant information.

   The use of specific capacity data to supplement aquifer test-derived transmissivity
    data is appropriate for the Denver Basin alluvial and bedrock aquifers.

   Other than a few storativity point values in the Douglas County region in the
    Arapahoe and Laramie-Fox Hills Aquifers, only the Robson (1983) storativity
    contours provide data for the storativity of the Denver Basin aquifers. This could




                                            22
   have important implications for evaluating the water supply and for conducting
   groundwater modeling of these aquifers in the future.


It is anticipated that this Technical Memorandum will be updated with data collected in
future Phases of the SPDSS.


Recommendations
Denver Basin Alluvial Aquifer
   Perform a multi-well aquifer test or tests in the mainstem of the South Platte
      River between Kersey and Orchard and perform several in the Kiowa and Bijou
      Creek drainages in the alluvial aquifer.

      Collect additional specific yield data from the alluvial aquifer along the
       mainstem of the South Platte River downstream of Greeley and within the Lost
       Creek and Kiowa-Bijou Designated Basins.

      Work with cooperating municipalities or other groundwater users to obtain
       additional aquifer property data from the alluvial aquifer overlying the Denver
       Basin. This activity is planned for Phase 2 of the SPDSS.

Denver Basin Bedrock Aquifers
   Attempt to obtain source data and methods used to determine hydraulic
      conductivity provided in Robson (1983).

      Perform additional data analysis to convert existing transmissivity data to
       hydraulic conductivity data for data for which this has not been undertaken.
       This activity would require information on the aquifer saturated thickness for
       individual data points and could add significant value to the SPDSS project.

      Perform additional aquifer tests or collect additional existing aquifer hydraulic
       conductivity data, if available, for the Upper and Lower Dawson Aquifers , in the
       Denver Aquifer in the vicinity of southwestern Elbert and southeastern Douglas
       Counties, and in the Upper or Lower Arapahoe Aquifers especially southeast of
       DIA and in western Elbert and eastern El Paso Counties, to fill large data gaps in
       these areas. Additional bedrock aquifer tests and collection of bedrock aquifer
       property data are planned for these areas in Phase 2 of the SPDSS.

      Obtain additional storativity data where possible in all aquifers. There are few
       data of this type reported for any of the aquifers in the entire Denver Basin
       Region yet this is an important parameter for determining the amount of water
       present in the aquifers and for estimating their water supply potential. The only
       location these data are not needed is in the Arapahoe and Laramie-Fox Hills
       Aquifers in the vicinity of Highlands Ranch in northern Douglas County.


                                           23
       Additional bedrock aquifer pumping tests capable of providing storativity data
       are planned for Phase 2 of the SPDSS.


References
Barkmann, P. E., and Edington, D. H., 2001. Results of Vertical Permeability
Measurements from Core Sample and Multiple Aquifer Monitoring During Pumping
Tests in the Vicinity of Parker, Colorado. Conference Proceedings, Troubled Waters,
Denver Basin at Risk, Denver, Colorado November 28, 2001.

Barkmann, P. E., 2003. Personal communication with Andy Horn of CDM, June 20,
2002.

Bjorklund and Brown. 1957. Geology and Ground-Water Resources of the Lower South
Platte River Valley Between Hardin Colorado, and Paxton, Nebraska. USGS Water
Supply Paper 1378.

Boulton, N. E., 1963. Analysis of Data from Non-Equilibrium Pumping Test Allowing
for Delayed Yield from Storage. Proceedings of the Institute for Civil Engineers, Vol. 26
(London).

Colorado Department of Natural Resources, Division of Water Resources (DWR), 1985a.
Rules and Regulations Applying Exclusively to the Withdrawal of Ground Water from
the Dawson, Denver, Arapahoe, and Laramie-Fox Hills Aquifers in the Denver Basin
(Denver Basin Rules).

Colorado Department of Natural Resources, Division of Water Resources (DWR), 1985b.
Technical Appendices to Denver Basin Rules.

Duke, H. R. and Longenbaugh, R. A. 1966, Evaluation of Water Resources in Kiowa and
Bijou Creek Basins, Colorado. Prepared by Colorado State University for the Colorado
Water Conservation Board, May 1966.

Erker, H. W. and Romero, J. C. 1967. Groundwater Resources of the Upper Black
Squirrel Creek Basin, El Paso County, Colorado, Prepared for the Colorado
Groundwater Commission, January 1967.

Emmons, S.F., Cross C.W., and Eldridge, G.H. 1896. Geology of the Denver Basin: USGS
Mon. 27.

Fetter, C. W., 2001. Applied Hydrogeology, Third Edition, McMillan Publishing
Company.

Halepaska & Assoc., 1997. Final Report, Denver Basin Recharge Demonstration Project,
Prepared for the United States Bureau of Reclamation, Billings Montana, Project No.
5246h.


                                           24
Hill, 1991. Aquifer Storage Recovery Feasibility Investigation, Prepared for the
Centennial Water and Sanitation District, Highlands Ranch, Colorado by CH2M Hill.

Hiller, D.E., Brogden, R.E. and Schneider, P.A., Jr., 1978. Hydrology of the Arapahoe
Aquifer in the Englewood-Castle Rock Area, South of Denver, Denver Basin, Colorado,
USGS Miscellaneous Investigation Map I-1043.

Hurr, R.T. and Schneider, P., 1972a. Hydrogeologic Characteristics of the Valley-Fill
Aquifer in the Brighton Reach of the South Platte River Valley, Colorado, USGS Open-
File Report 72-332.

Hurr, R.T. and Schneider, P., 1972b. Hydrogeologic Characteristics of the Valley-Fill
Aquifer in the Greeley Reach of the South Platte River Valley, Colorado, USGS Open-
File Report 73-124.

Hurr, R.T., and Schneider, P.A.,1972c. Hydrogeologic Characteristics of the Valley-Fill
Aquifer in the Weldona Reach of the South Platte River Valley, Colorado, USGS Open-
File Report 73-127.

Lapey, 2001. Hydrogeologic Parameters of the Kiowa Research Core, Kiowa, Colorado,
Master's Thesis, Colorado State University.

McConaghy, J.A., Chase, G.H, Boettcher, A.J., and Major, T.J., 1964. Hydrogeologic Data
of the Denver Basin, Colorado, CWCB Basic Data Report 15.

Major, T. J., Robson, S. G., Romero, J. C., and Zawistowski, S., 1983. Hydrogeologic Data
from Parts of the Denver Basin, Colorado, USGS Open File Report 83-274.

Mulhern, MRE 2003. Personal correspondence from Pat Mulhern to Andy Horn
regarding the South Metro Water Supply Study.

Nelson, Haley, Patterson, & Quirk, Inc. (NHPQ) 1967. Ground Water Resources of the
Lost Creek Drainage Basin, Weld, Adams, and Arapahoe Counties, Colorado. Prepared
for the Colorado Ground Water Commission by Nelson, Haley, Patterson, & Quirk, Inc.,
Consulting Engineers and Geologists, June 1967.

Razak, M. and Huntley, D., 1991. Assessing Transmissivity from Specific Capacity in a
Large and Heterogeneous Alluvial Aquifer, Groundwater, Vol 29, No. 6

Robson, S.G., 1996. Geohydrology of the Shallow Aquifers in the Denver Metropolitan
Area, Colorado. USGS Hydrologic Invest Atlas HA-736.


Robson, S.G., 1987. Bedrock Aquifers in the Denver Basin, Colorado - A Quantitative
Water-resources Appraisal. USGS Professional Paper 1257.




                                           25
Robson, S.G., 1983. Hydraulic Characteristics of the Principal Bedrock Aquifers in the
Denver Basin, Colorado. USGS Hydrologic Investigations Atlas HA-659.
Robson, S. G., and Banta, E. R., 1993, Data from Core Analyses, Aquifer Testing, and
Geophysical Logging of the Denver Basin Bedrock Aquifers at Castle Pines, Colorado.
USGS Open File Report 93-442.

Robson, S. G., and Banta, E. R., 1990. Determination of Specific Storage by Measurement
of Aquifer Compression Near a Pumping Well, Ground Water, Vol. 26, No. 6.

Robson, S.G., and Romero, J.C., 1981a. Geologic Structure, Hydrology, and Water
Quality of the Dawson Aquifer in the Denver Basin, Colorado. USGS Hydrologic
Investigations Atlas HA-643.


Robson, S.G., and Romero, J.C., 1981b. Geologic Structure, Hydrology, and Water
Quality of the Denver Aquifer in the Denver Basin, Colorado. USGS Hydrologic
Investigations Atlas HA-646.


Robson, S.G., Romero, J.C., and Zawistowski, S., 1981. Geologic Structure, Hydrology,
and Water Quality of the Arapahoe Aquifer in the Denver Basin, Colorado. USGS
Hydrologic Investigations Atlas HA- 647.


Romero, J. C. , 1976. Ground Water Resources of the Bedrock Aquifers of the Denver
Basin, Colorado, Office of the State Engineer, Division of Water Resources.

Schneider, P.A., Jr. 1962. Records and Logs of Selected Wells and Test Holes, and
Chemical Analyses of Ground Water in the South Platte River Basin in Western Adams
and Southwestern Weld Counties, Colorado, CWCB Basic Data Report 9.

Smith, R.O, Schneider, P.A., Jr., and Petri, L.R., 1964. Ground-Water Resources of the
South Platte River Basin in Western Adams and Southwestern Weld Counties Colorado,
USGS Water-Supply Paper 1658.

Topper, R. 2003. Groundwater Atlas of Colorado, Colorado Geological Survey

Willard Owens Associates. 1971. Ground Water Resources of the Big Sandy Creek
Drainage Area Southeastern Colorado. Prepared for the Colorado Division of Water
Resources. March 1971.

Wilson, W. W. 1965. Pumping Tests in Colorado, CWCB Circular 11.




                                           26
                                      Appendix A
          Data Directory for Denver Basin Region Aquifer Properties

Table Name: WELL          Task: Task 42, 43 and 44 of the SPDDS
Description: The core table in the database containing key information on wells in SPDSS Study Region including
location, permit number, receipt, name, depth, aquifer tapped, and perforated interval. Data in this table was
obtained from the SEO and other published databases. CDM added several new fields to this table, as indicated
in the Technical Memorandum.
Field Name                Field Description
well_id                   Unique well identifier.
well_name                 Well name.
div                       SEO water division.
wd                        SEO water district.
id                        SEO structure ID.
receipt                   Well application receipt number.
permitno                  Well permit number.
permitsuf                 Well permit suffix.
permitrpl                 Well permit replacement code.
county                    SEO county number. ([county_ref].[cty])
PM                        Principle meridian. (S = Sixth; N = New Mexico; U= Ute; C = Costilla; B= Baca)
ts                        Township number.
tsa                       Half Township identifier. (H)
tdir                      Township direction (N/S).
rng                       Range number.
rnga                      Half Range identifier. (H)
rdir                      Range direction (E/W).
sec                       Section number. (1-36)
seca                      Upper section identifier. (U)
q160                      160 acre quarter.
q40                       40 acre quarter.
q10                       10 acre quarter.
coordsns                  Distance from north/south section line (feet)
coordsns_dir              Direction of measurement from north/south section line.
coordsew                  Distance from east/west section line (feet)
coordsew_dir              Direction of measurement from east/west section line.
utm_x                     The x (Easting) component of the Universal Transverse Mercator system.
utm_y                     The y (Northing) component of the Universal Transverse Mercator system.
elev                      Well elevation at ground surface.
loc_accuracy_num          Indicate source of UTM coordinates (GIS, Spotter, Digitize)
aquifer1                  Aquifer that the well is completed in. ([aquifer].[aquifer_code])
aquifer2                  Aquifer that the well is completed in. ([aquifer].[aquifer_code])
aquifer_comment           Aquifer assignment comment noting why or why not able to assign to specific aquifer.
tperf                     Top perforated interval of well casing. (Feet from ground level)
bperf                     Bottom perforated interval of well casing. (Feet from ground level)
yield                     Well yield (GPM)
depth                     Well depth. (Feet from ground level)
spdss_region              SPDSS region code (Denver Basin, LSPAR)
elev_accuracy_num         Indicate source of elevation coordinates
well_owner                Well owner



                                             27
Table Name: WELL_DATA SOURCE              Task: Task 42, 43 and 44 of the SPDDS
Description: Table containing each well in the database indicating the original database source and a well
identifier.
Field Name                                Field Description
well_id                                   Unique well identifier.
data_source                               Well data source (DWR, USGS, USBR, etc)
identifier                                Source's well identifier.




Table Name: PUMP_TEST           Task: Task 42 and 43 of the SPDSS
Description: Table containing available pump test data.
Field Name                      Field Description
well_id                         Unique well identifier.
testdate                        Date of pump test.
toptestint                      Top of tested interval. (Feet from ground level)
basetestint                     Base of tested interval. (Feet from ground level)
                                Pre-test static water level. (Feet from ground level) Pressure head above
tswl                            ground level is given as negative value.
tfwl                            Post-test final water level. (Feet from ground level)
drawdown                        Change in feet between pretest water level and end of test water level.
testq                           Average testing discharge rate. (GPM)
testtime                        Duration of the aquifer test. (HOURS)
trans                           Estimate transmissivity. (GPD/FT)
k                               Hydraulic conductivity. (FT/DAY)
                                Storativity (dimensionless- can only be calculated from confined aquifer
storativity                     tests with one or more monitoring wells)
leakance                        Composite leakance between aquifer layers in units of 1/DAYS.
ptsource                        Entity reporting the pump test date.
pttype                          Pump test type. (Pumping, recovery slug, flow, lab, other)
ptmon                           Indicates observation point available for test.
                                Check box indicating if the pump test included observation well data.
                                Observation wells must be screened in the same aquifer as the pumping
ptobs                           well.
                                Check box indicating if the data point was the observation well used in an
ptobs_well                      aquifer test.
ptmultiple                      Flag indicating the presence of multiple pump tests available for a well.

sp_cap                          Calculation of specific capacity. (Discharge in GPM)/(Feet of drawdown)
sp_yield                        Specific Yield. (Decimal %)
porosity                        Porosity. (Decimal %)
B                               Saturated thickness. (FEET)
comments                        Miscellaneous information.




                                              28
Database Key Tables

REF_ELEV_ACCURACY
 elev_accuracy_num Description
          1        Original database
                   USGS 30-meter
          2        DEM
          3        Surveyed

REF_LOC_ACCURACY
 loc_accuracy_num Description
         1        Spotted from PLSS quarters
         2        Spotted from PLSS distances from section lines
         3        GPS
         4        Digitized
         5        Original database




                                            29

				
DOCUMENT INFO