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Groundwater Pumping Tests, CS-10 and CS-16

Section 3 - Pumping Test Methodology and Analysis

This section describes various components and results of the pumping test analysis program implemented for the project. The field investigation program was initiated on July 16, 2001 and completed on August 13, 2001. Several wells included in the analysis received various upgrades to facilitate performing the pumping test program. Upgrades were implemented for wells CS-9, CS-10, CS-11, and CS-16 as summarized in Table 2.

Table 2 - Summary of Well Upgrades

Barometric pressure fluctuations were monitored throughout the pumping test program to determine if atmospheric pressure had any impact on groundwater levels. The barometric sensing transducer was installed within the casing of CS-3 at a depth of 30 feet below ground surface (bgs). Figure 2 presents a graph illustrating barometric pressure changes with respect to time that occurred over the course of the investigation. During the testing period, the weather remained steady (hot and dry) without any precipitation events. Diurnal effects related to the daily heating and cooling of the atmosphere are evident as a recurring cycle during the recording period. Otherwise, changes to barometric pressure were minimal during the field investigation period. Actual barometric pressure readings ranged from 28.64 inches-Hg to 29.02 inches-Hg over the course of the project. Therefore, barometric pressure was not interpreted as an influential factor during the pumping test.

The following sections detail the investigation programs and results for the CS-10 and CS-16 analysis on an individual basis.

3.1 - CS-10

CS-10 is a 559-foot deep drinking water supply well that is completed with 390 feet of surface casing and was used as the pumping well for this investigation. The Lower Glen Rose, Bexar Shale, and Cow Creek formations contribute water to the CS-10 borehole. CS-9 and CS-11 are also open Glen Rose, Bexar Shale, and Cow Creek completions and are located southwest and northwest of CS-10, respectively. CS-9 and CS-11 were used as observation wells during the investigation.

The locations of these wells are included on Figure 1. The findings and results of the various activities conducted in association with the investigation are presented at the conclusion of each respective sub-section below, and overall program conclusions area summarized in Section 4.0.

3.1.1   CS-10 Drawdown Test

A 48-hour drawdown test was conducted for CS-10 to identify the optimum pumping rate to be implemented for the 72-hour pumping test. However, because CSSA water supply personnel reported they never experienced CS-10 being pumped dry, it was agreed to forego the stepped approach and conduct the drawdown test analysis with the well system operating at full capacity. Groundwater produced during the drawdown test was discharged to the CSSA potable water distribution system reservoir. Because CS-10 did not contain an e-line or a pressure transducer tube, water level measurements were obtained using an air-line/pressure gauge with the water depth determination being a function of the amount of air pressure required to evacuate water from within the air-line. CSSA reported that the air-line tube extended to a depth of 520 feet below the top of the well. Air pressure measurements were converted to water depth using the following equation:

Water Depth = 520 � (2.31 x equilibrium psi)

Where:

520 = total depth of the air-line referenced to the top of the well casing

2.31 = feet of water equivalent to one pound per square inch (psi)

equilibrium psi = the psi pressure required to evacuate the water column from within the air-line tube

Parsons obtained depth to water (as a function of the air pressure required to evacuate the water column within the air-line tube) versus elapsed time, well discharge rate, and total discharge measurements for CS-10 during the drawdown test. Depth to water measurements versus elapsed time were also documented within CS-9 and CS-11 using electronic water level meters (e-line). Attachment A presents the field measurement reports generated for each of the wells during the drawdown test.

The discharge capacity of the pumping system declined from 94 gallons per minute (gpm) at the start of the drawdown test to 85 gpm 24 hours into and throughout the remainder of the test. CS-9 and CS-11 responses to pumping were 13.77 ft and 2.48 ft of drawdown, respectively, during the course of the drawdown analysis. Although CS-10 experienced 64.68 ft of decline during the test, well drawdown equilibrium was not reached during the 48-hour test. Based on these results, Parsons decided to perform the 72-hour pumping test using 80 gpm as the pumping rate. This rate was selected to increase the potential for reaching drawdown equilibrium while still imparting sufficient stress to the aquifer system to maximize the pumping test results.

After the drawdown test was completed, CS-10 was outfitted with a pressure transducer tube. This was done to facilitate the collection of water level data and reduce uncertainties inherent to the air-line/pressure gauge method.

3.1.2   Regional Groundwater System Trend Identification

Parsons conducted an analysis to identify the regional Middle Trinity aquifer groundwater level fluctuation trend prior to the 72-hour pumping test. This was conducted in preparation for adjusting water level measurements obtained during the pumping test to account for regional changes in water level that occurred during the test.

Pressure transducers were installed within CS-9, CS-10, and CS-11 to record changes in water level over time for a period beginning 4 days before conducting the 72-hour pumping test. Figure 3 illustrates a water level versus time graph developed for each of the wells included within the analysis prior to conducting the CS-10 pumping test.

As shown on Figure 3, groundwater levels associated with each of the wells included within the analysis exhibited a declining trend prior to the pumping test. This observation is consistent with the expected trend as the site area was experiencing drought conditions prior to and during the field investigation program. This condition coupled with the field program coinciding with the peak groundwater well withdrawal season for the area, was responsible for the declining water level trend identified during the background analysis.

As shown on Figure 3, the water level decline trend appeared consistent within each of the three wells included within the background monitoring program. The reduction in water level appears consistent from well to well as evidenced by consistent slopes associated with each of the water level versus time trend lines (Figure 3). Based on that observation, Parsons selected the trend line associated with CS-10 to represent the linear equation associated with the regional water level decline trend. Figure 4 illustrates the linear equation of the CS-10 trend line as calculated by Excel^TM as a regional decline of 1.0613 feet per day.

The linear equation defined for the regional water level decline trend illustrates the relationship of regional water level decline versus time. This relation was used to adjust the depth to water readings obtained during the pumping test to account for the regional water level decline that occurred during the test using the following equation:

CWL = MWL � (1.0613 x ET)

Where:

CWL = corrected water level (feet below top of casing)

MWL = measured water level (feet below top of casing)

1.0613 = regional decline (feet per day) from Figure 4

ET = elapsed time since the start of the test (days)

This action allowed aquifer property computations to proceed as if the regional aquifer was under static conditions throughout the pumping/recovery test performance time period.

3.1.3   CS-10 Pumping/Recovery Test

Parsons personnel executed the pumping/recovery test for CS-10 between July 30 and August 6, 2001. The initial 72 hours of the test consisted of an analysis of aquifer water level drawdown with respect to elapsed time associated with removing groundwater from CS-10 at a constant rate of 80 gpm. Groundwater recovery was monitored upon completion of the 72-hour pumping test.

Groundwater level with respect to time was monitored within CS-9, CS-10, and CS-11. Depth to water measurements were obtained within observation wells (CS-9 and CS-11) using pressure transducers. Depth to water measurements were obtained with an e-line within the pumping well. E-line measurements were also conducted periodically within the observation wells to verify accuracy of the pressure transducer readings. E-line and transducer readings were consistent throughout the program. 

Groundwater pumping rates and discharge totals were monitored via a flow meter/totalizer installed along the CS-10 discharge piping. Discharge rate was monitored throughout the pumping test and was adjusted as needed to maintain the 80 gpm flowrate. A total of 341,679 gallons of groundwater were pumped over the duration of the test.

Groundwater discharge was routed to the CSSA potable water system. Water was forwarded to the potable water storage tank. Once the storage tank was filled, water was discharged from the storage tank to D-Tank at a rate consistent with the pumping rate. Parsons installed a turbine flow meter/totalizer within the discharge pipe leading to D-Tank to measure the volume of fluid discharged from the potable water system to the tank. A total of 140,722 gallons of water was discharged from the CSSA potable water distribution system into D-Tank during the pumping test.

Figure 5 is a graph depicting corrected water level versus elapsed time for CS-9, CS-10, and CS-11 during the pumping/recovery test period. As shown on
Figure 5, responses to pumping were exhibited within CS-9 and CS-10. CS-11 did not respond to pumping as exhibited by the consistent trendline slope for CS-11 during the pumping/recovery test period. Parsons speculates that the reason for the absence of response to pumping exhibited at CS-11 is related to an aquifer barrier boundary condition located between CS-10 and CS-11 that also extends between CS-9 and CS-11. Although the precise explanation for the boundary condition is currently unknown, this data is interpreted as evidence that the Middle Trinity aquifer is not isotropic. Potential explanations for the boundary conditions include:

Figures 6 and 7 present semi-log plots of corrected water level drawdown/recovery with respect to elapsed time identified within CS-9 and CS-10, respectively, during the CS-10 pumping test program. As shown on Figure 7, approximately 71 feet of total groundwater drawdown (corrected) was measured within CS-10 in association with the pumping test. Using the total drawdown and discharge rate, specific capacity for CS-10 is calculated using the following equation:

SC = Q/Dh

Where:

SC = specific capacity

Q = well discharge rate

Dh = total drawdown

Attachment B presents the specific capacity calculations conducted with respect to CS-10. As presented in Attachment B, the specific capacity of CS-10 was calculated as 1.13 gpm/ft.

Figure 7 illustrates that the CS-10 drawdown trend line varies from linear within the later stages of the pumping test beginning shortly after 1,000 minutes into the test. This is interpreted as possibly being related to the manifestation of the boundary condition responsible for no response to pumping identified within CS-11. Potential response related to this boundary condition was identified approximately 2,500 minutes later in the drawdown curve of CS-9. The magnitude of the boundary condition associated with the CS-9 drawdown curve (Figure 6) is significantly less than that associated with the CS-10 curve. These two observations are interpreted as evidence suggesting the physical location of the boundary condition is closer to CS-10 than CS-9 with respect to CS-11. This interpretation leads to a conclusion that orientation of the boundary condition is skewed in the east to west direction more than in the north to south direction. 

A second interesting observation identified upon comparing Figure 6 with Figure 7 is related to differing responses to recharge exhibited by these wells. As shown on Figure 7, the slope of the recovery curve associated with CS-10 is very steep with much of the recovery occurring within 1,000 minutes of shutting down the pump. In comparison, the recovery trend line slope for CS-9 remains less steep (but more linear) throughout the recovery period. Increased storage capacity in the immediate vicinity of CS-10 due to the prior acidization of the well may also contribute to the rapid recharge effect. During the rebound stage, CS-10 recovered 91 percent, and CS-9 recovered 100 percent (corrected for regional decline).

Analysis of transmissivity (T) and storativity (S) was conducted with respect to CS-9 and CS-10 utilizing the Theis equation. AQTESOLV For Windows^TM version 3.01 was employed for the Theis equation calculations. The Theis equation is based on the following assumptions:

Obviously, the Theis equation is based on conditions principally achievable in a laboratory setting because true aquifer systems will seldom meet all the criteria formulating the basis of the Theis solution. Nevertheless, the Theis equation is considered valid for most pumping test analyses as the margin of error associated with not meeting the above criteria in a natural setting is usually considered negligible without a significant impact on the results. Parsons identified the Theis solution to be valid for this study.

Various well construction details required as input parameters into AQTESOLV were obtained from the existing CSSA database and summarized within Volume 5-2, Groundwater, Water Well Survey. Two input parameters required by AQTESOLV were unknown at the time of the analysis and were therefore assumed. The assumed parameters included the:

The ratio K_z/K_r was assumed as unity for the analysis. The diameter of the open-hole section of CS-10 was assumed to be 8 inches. Of these two assumptions, the value with the highest potential for impact on T and S value results was the K_z/K_r input parameter. A sensitivity analysis was conducted to identify the impact to T and S results while substituting the smallest value for K_z/K_r available (0.001) for inclusion within AQTESOLV. The results identified T and S values to be within 20 percent of the T and S values obtained using the assumed unity value for K_z/K_r. The sensitivity analysis identified a direct relationship between K_z/K_r value and T/S values. Reducing the K_z/K_r value (i.e. representing an increased K horizontal vs. K vertical) yields lower T and S values. Based on stated intended use of the preliminary T and S data generated by this investigation, Parsons is of the opinion that using K_z/K_r = 1 yields the most usable results.

AQTESOLV input values of aquifer saturated thickness were derived by assuming that the depth to water measurement at the start of the pumping test was representative of the static water level coupled with stratigraphic information obtained from Parsons (1993), summarized within the literature review section of this report. The saturated thickness was determined to be the distance from the static water level to the lower contact of the Cow Creek Formation minus the thickness of the Bexar Shale. The Bexar Shale was excluded because this unit is not a major groundwater production zone. Attachment C presents the aquifer saturated thickness value calculation utilized for the CS-10 analysis.

Attachment D presents the aquifer analysis curve and associated report generated by AQTESOLV in association with the CS-10 pumping test analysis program. Depth to water observations obtained during the conductance of the pumping/recovery test are included in the report generated by AQTESOLV. Visual curve matching was conducted to increase the accuracy of T and S values generated from the pumping test data. As presented within Attachment D, transmissivity and storativity values identified for the Middle Trinity aquifer based on the CS-10 analysis, are 2,400 gpd/ft and 0.0005, respectively. The value of storativity determined from the CS-10 pumping test suggests that water-producing intervals are under confining conditions.

Using transmissivity (2,400 gpd/ft) and saturated thickness (198 ft), hydraulic conductivity may be calculated using the following equation:

K=T/b

Where:

K = hydraulic conductivity

T = transmissivity

b = saturated thickness

Hydraulic conductivity calculations for the Middle Trinity aquifer in the CS-10 area are presented in Attachment E. As presented, the hydraulic conductivity of the Middle Trinity aquifer was calculated as 12.12 gpd/ft² or 5.7 x 10^-4 centimeters per second (cm/sec) at CS-10.

3.2 - CS-16

Investigation activities associated with the CS-16 analysis were consistent with the activities implemented for CS-10. One exception included conducting the drawdown test for CS-16 as a series of pumping steps rather than initiating the test at full well system capacity. The reason for conducting the drawdown test using steps is that, unlike CS-10, CSSA water supply personnel had limited historical knowledge of the performance of CS-16 as this well had been removed from the facility potable water supply system in 1991.

The remainder of the investigation activities conducted for the CS-16 pumping test were consistent with those implemented for the CS-10 pumping test. Investigation activities included conducting a program designed to identify the regional groundwater system water level trend followed by performing a pumping/recovery analysis as described in the following paragraphs. The wells included within the various phases of the CS-16 analysis were CS-16, CS-D, CS-2, CS-3, CS-4, CS-MW1-LGR, CS-MW2-LGR, CS-MW3-LGR, CS-MW4-LGR, CS-MW5-LGR, CS-MW9-LGR, CS-MW9-BS, and CS-MW9-CC. The locations of these wells are included in Figure 1. The findings and results of the various investigation activities conducted in association with the investigation are presented at the conclusion of each respective sub-section below. 

3.2.1   CS-16 Step-Drawdown Test

Parsons conducted a step-drawdown test for CS-16 on July 25, 2001. The purpose of the test was to determine the optimum pumping rate to be employed for the 72-hour pumping test. Water level drawdown versus elapsed time measurements were obtained using a pressure transducer installed within CS-16. Discharge rate and total flow measurements were monitored via an in-line turbine meter. A ball valve was installed downstream of the flow meter to allow adjustment of the discharge rate.

Three pumping steps, each lasting approximately 2 hours, were completed during the approximate 7.5-hour long test. The pumping rate associated with the various steps were:

A fourth step was initiated at full pump capacity (approximately 57 gpm). Discharge rates were identified to vary significantly during the fourth step, rendering this step of the analysis unusable in the evaluation. The reason was that a constant discharge rate could not be maintained as drawdown increased, resulting in a gradually decreasing flowrate. For this reason, the fourth step of the analysis was terminated early.

Discharge water generated during the step test was routed through two, 50 gpm capacity, granular activated carbon (GAC) units, piped in parallel, prior to piping the discharge water to an existing HDPE-lined pond located in an adjacent site area (SWMU B-10 as shown on Figure 1). Discharge water samples were obtained both upstream and downstream of the GAC units to evaluate performance of the units. Analytical lab results associated with water samples collected during the step test are presented in Attachment F. Table 3 summarizes the analytical testing results.

Table 3 - GAC System Performance Analytical Testing Summary During Step Test

As shown in the above table, the GAC units were successful in removing the VOC of concern to below MCLs. 

Attachment G presents the depth to water level versus elapsed time data file report generated during the CS-16 step test. Notations are included within the report denoting the start and end times associated with each of the pumping steps conducted for the program. Figure 8 is a graphic representation of the depth to water versus elapsed time during the step-drawdown test.

CS-16 experienced 24.47 feet of drawdown during Step 1, 37.42 feet of drawdown during Step 2, and 49.7 feet of drawdown during Step 3. As shown on Figure 8, the slope of the trend lines associated with each of the steps conducted for the analysis are fairly consistent, and relatively steep, throughout each step. This was interpreted upon completion of the step test, as evidence suggesting that the amount of time required for the well drawdown to reach equilibrium using discharge rates near full well capacity could extend greater than the planned 72-hour pumping period.

The pumping rate employed for the 72-hour test was chosen as 45 gpm. This rate was selected to increase the potential for reaching drawdown equilibrium within the 72-hour pumping period while at the same time effectively stressing the aquifer system to yield a maximum radius of influence for the aquifer analysis. This rate also allowed the GAC units to function in a series configuration at a small volume below maximum capacity thereby increasing the effectiveness of the GAC toward reducing VOC concentrations to concentrations below MCLs.

3.2.2   Regional Groundwater System Trend Analysis

Parsons conducted an analysis to identify the regional groundwater level fluctuation trend prior to the 72-hour pumping test. Pressure transducers were installed within several wells located throughout the CS-16 area. The wells included within the regional groundwater fluctuation trend analysis included CS-D, CS-2, CS-3, CS-4, CS-MW1-LGR, CS-MW2-LGR, CS-MW3-LGR, CS-MW4-LGR, CS-MW5-LGR, CS-MW9-LGR, CS-MW9-BS, and CS-MW9-CC. The pressure transducers were employed to obtain depth to water level information prior to conducting the 72-hour pumping test. This was conducted in preparation for adjusting water level measurements obtained during the pumping test to account for regional changes in water level that occurred during the test. 

Figure 9 presents a graph illustrating depth to water versus time for several wells included within the CS-16 analysis during the 9-day period prior to initiating the CS-16 pumping test. Pressure transducers installed within wells CS-MW4-LGR and CS-MW5-LGR malfunctioned during the initial portion of the regional trend analysis; therefore, comprehensive background data from these wells are not available. As shown on Figure 9, a consistent trend of regional water level decline was experienced within each of the wells as exhibited by consistent water level versus time graph slope. The rate of constant decline ranged from 0.8 to 1.2 feet per day, for 20 days prior to the test. CS-D was selected for the determination of the linear equation associated with the regional groundwater trend for the 6 days prior to the pumping test. 

Figure 10 illustrates the linear equation of the CS-D trend line as calculated using Excel. From this, a correction factor was used to adjust the depth to water readings obtained during the pumping test to correct for regional water level decline that occurred during the test. Water level correction was conducted using a decline of 0.665 feet per day as the water level versus time ratio within the equation presented in Section 3.1.2. This action allowed aquifer property computations to proceed as if the regional aquifer was under static conditions throughout the pumping/recovery test analysis.

3.2.3   CS-16 Pumping/Recovery Test

Parsons personnel executed the pumping/recovery test for CS-16 between August 6 and August 10, 2001. The initial 72 hours of the test consisted of an analysis of aquifer water level drawdown with respect to time associated with removing groundwater from CS-16 at a constant rate of 45 gpm. The groundwater recovery rate was monitored for approximately 20 hours within CS-16 following the 72-hour pumping test. Groundwater recovery was measured for a significantly longer period (approximately three additional days) within CS-D. Groundwater level with respect to time was also monitored within wells CS-2, CS-3, CS-4, CS-MW1-LGR, CS-MW2-LGR, CS-MW3-LGR, CS-MW4-LGR, CS-MW5-LGR, CS-MW9-LGR, CS-MW9-BS, and CS-MW9-CC throughout the CS-16 test.

Depth to water measurements were obtained within the various observation wells using pressure transducers. Depth to water measurements were obtained with an electronic water level meter (e-line) within the pumping well. E-line measurements were also conducted periodically within the observation wells to verify accuracy of the pressure transducer readings. E-line measurements were consistent with transducer readings thus validating the pressure transducer readings.

Groundwater pumping rates and discharge totals were monitored via a flow meter/totalizer installed along the CS-16 discharge piping. Discharge rate was monitored throughout the pumping test and was adjusted as needed.

Groundwater discharge was routed through two 50 gpm capacity GAC units, piped in series, prior to routing into the CSSA potable water distribution for transport and discharge to an area located within the CSSA facility approximately 4,800 feet south of CS-16 (Figure 1). Prior to discharge, CSSA personnel isolated the section of the potable water distribution system used to transfer water produced from CS-16 from the remainder of the distribution system network. Discharge water samples were obtained on a once per 24-hour period basis to document efficiency of the GAC system toward reducing the concentrations of contaminants of concern (COC) to below MCLs. Each sampling event consisted of three samples collected at the wellhead, after the first GAC canister, and after the second GAC canister. Analytical lab reports associated with water samples collected during the pumping test are presented in Attachment H. Table 4 summarizes the daily discharge sample analytical results.

As shown in Table 4, COCs were not detected at concentrations exceeding State or Federal SDWA MCLs in samples obtained midstream and downstream of the GAC system.

Discharge quantities were monitored at two locations during the pumping analysis. The total amount of water discharged at the pumping well was measured as 190,156 gallons at CS-16. The total amount of water discharged from the potable water distribution system was measured as 196,777. The additional 6,621 gallons discharged through the potable water system consisted of potable water used to flush residual pumping test water entrained within the distribution system upon completion of the pumping test. 

Water produced from CS-16 was discharged from the potable water distribution system via an opened fire hydrant to the ground surface in an area located approximately 4,800 feet south of CS-16. Subcontractor personnel constructed berms within the area where water produced during the pumping test was discharged onto the ground surface to reduce the potential for discharge water migration toward a dry creek bed located 900 feet to the east. 

Figure 11 presents a graph depicting water level versus elapsed time for the observation wells included within the CS-16 pumping/recovery analysis. As shown on Figure 11, responses to pumping were exhibited within CS-16 and CS-D only. The remainder of the observation wells did not respond to pumping as shown on Figure 11.

Table 4 - GAC System Performance Analytical Testing Summary During Pumping Test

Figures 12 and 13 present semi-log plots of corrected water level drawdown/recovery with respect to elapsed time identified within CS-16 and CS-D, respectively. As shown on Figure 12, approximately 63 feet of total groundwater drawdown was measured within CS-16 in association with the pumping test. Using the total drawdown (63 ft) and discharge rate (45 gpm), the specific capacity for CS-16 was calculated using the following equation:

SC = Q/Dh

Where:

SC = specific capacity

Q = CS-Discharge rate

Dh = total drawdown

Attachment I presents the specific capacity calculations conducted with respect to CS-16. As presented, the specific capacity of CS-16 was calculated as 0.71 gpm/ft.

A comparison of the drawdown portions of the curves associated with CS-16 (Figure 12) and CS-D (Figure 13) identify the drawdown curves as intersecting a boundary condition at about 1,200 to 1,500 minutes into the pumping test. This observation is evident by the change in slope of the drawdown trend line for each of the two wells. The slope change is more prominently displayed at CS-D than at CS-16. This is interpreted as evidence that the location of the boundary condition is closer to CS-D than to CS-16. Potential explanations for the boundary conditions include those previously mentioned in Section 3.1.3. The trend line slope deviation identified during the initial 30 minutes of drawdown at CS-16 (Figure 12) is related to changes in water levels resulting from initial pump discharge rate adjustment.

A comparison of the recovery portions of Figures 12 and 13 identifies nothing of significance until approximately 5,000 minutes after the start of the test. Recovery data in both CS-16 and CS-D show a decrease in recharge rate, followed by a decline in water level at CS-D. Recovery data collection for CS-16 had ceased prior to this time. Water levels were identified to be dropping within CS-D after about 7,000 minutes as shown on Figure 13. It is unlikely to be related to any on-site pumping since no measurable effect was noted in CS-D during the CS-10 pumping test (see Figure 9). This is interpreted as being related to regional groundwater level trends and not to impacts related to well pumping occurring in other areas at CSSA.

Analysis of the aquifer transmissivity and storativity was conducted with respect to CS-16 and CS-D utilizing the Theis equation via the aid of AQTESOLV For Windows^TM version 3.01. Assumptions associated with the Theis equation were presented within the discussion relating to the CS-10 pumping/recovery test.

Various well construction details required as inputs into AQTESOLV were obtained from the existing CSSA database and summarized within Volume 5-2, Groundwater, Water Well Survey. Values of K_z/K_r were assumed as unity for reasons discussed in Section 3.1.3. Values of aquifer saturated thickness were derived by assuming that the depth to water measurement at the start of the pumping test was representative of the static water level coupled with stratigraphic information summarized within the literature review section of this report. The saturated thickness was determined as the distance from the static water level to the lower contact of the Cow Creek Formation minus the thickness of the Bexar Shale. The Bexar Shale was excluded because it is not a major groundwater production zone. Attachment J presents the saturated thickness determination calculations.

Attachment K presents the aquifer analysis graph and associated report provided by AQTESOLV as developed from data generated during the CS-16 pumping/recovery test program. As presented within Attachment K, transmissivity of the Middle Trinity aquifer was calculated to be 1,600 gpd/ft. Storativity was calculated as 0.00008. The value of storativity determined from the CS-16 pumping test suggests that the water-producing intervals are under confining conditions.

Using transmissivity (1,600 gpd/ft) and saturated thickness (178 feet), hydraulic conductivity may be calculated using the following equation:

K=T/b

Where:

K = hydraulic conductivity

T = transmissivity

b = saturated thickness

Hydraulic conductivity calculations for the Middle Trinity aquifer in the CS-16 area are presented in Attachment L. As presented, the hydraulic conductivity of the Middle Trinity aquifer was calculated to be 8.98 gpd/ft² or 4.2 x 10^-4 cm/sec for the CS-16 area.

3.2.4   Waste Management

Upon completion of the pumping test at CS-16, the activated carbon used to treat the discharged groundwater was sampled and profiled for waste characterization. The profile was accepted by Carbtrol Corporation, and the canisters with 2,000 pounds of activated carbon were returned for reactivation on November 20, 2001. The carbon was thermally reactivated on December 4, 2001. Attachment M contains the profiling, manifesting, transportation, and reactivation documents prepared during the waste management phase of the project.

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