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[December 2001 On-Post Groundwater Report Table of Contents]

December 2001

On-Post

Quarterly Groundwater Monitoring

Report

 Prepared For

Camp Stanley Storage Activity
Boerne, Texas

    Groundwater monitoring scoped under the AETC Contract F41689-96-D-0710, Delivery Order 5084, was performed the week of December 10, 2001, at CSSA.  Groundwater monitoring conducted under this order began at the June 2001 sampling event and continued through the December 2001 sampling event.  AFCEE/ERD and AFCEE/ERC provide technical oversight of the monitoring program.

    The current objectives of the groundwater-monitoring program are to determine groundwater flow direction and water levels, determine groundwater contaminant concentrations for characterization purposes, and identify seasonal variations in physical and chemical properties.  Appendix A identifies the DQOs for CSSA�s groundwater monitoring program, along with an evaluation of whether each DQO has been attained.  The objectives listed in the table also reference appropriate sections of the Order.  Overall DQOs for the investigations at CSSA are provided in Volume 1-1 behind the RFI Addendum tab (Section 11).

1.0             WATER LEVEL MEASUREMENTS

    Twenty-nine water level measurements and transducer data from CS-16 were recorded during the December 2001 monitoring event.  Water level measurements were taken in CSSA wells CS-1, CS-2, CS-3, CS-4, CS-9, CS-10, CS-11, CS-16, CS-D, CS-G, CS-H, CS-I, CS-MW1-LGR, CS-MW2-LGR, CS-MW3-LGR, CS-MW4-LGR, CS-MW5-LGR, CS-MW6-LGR, CS-MW6-CC, CS-MW6-BS, CS-MW7-LGR, CS-MW7-CC, CS-MW8-LGR, CS-MW8-CC, CS-MW9-LGR, CS-MW9-CC, CS-MW9-BS, CS-MW10-LGR, and CS-MW10-CC.  All water levels were measured with an e-line water level indicator.  An average groundwater elevation for well FO-20 from the week of December 14, 2001, was obtained from Fair Oaks Ranch Utilities.  Well CS-16 transducer data is discussed in section 3.0.

    Groundwater levels increased 15.46 feet on average between September 13, 2001, and December 10, 2001.  This overall increase was calculated by averaging the groundwater elevation changes for all wells, including those screened across multiple formations.  Groundwater elevations derived from water level measurements are measured against mean sea level and are summarized in Table 1-1.  Table 1-2 summarizes the changes in groundwater elevations since the September 2001 event.  The current groundwater elevations may be compared to the historical groundwater elevations from October 1992 through September 2001 shown in Table 3 of the Introduction to the Quarterly Groundwater Monitoring Program (Parsons 2001). 

    An average groundwater elevation for each formation in the Middle Trinity aquifer is provided in Table 1-1, calculated by using the groundwater elevations from wells screened only in that formation.  Generally at CSSA, the Lower Glen Rose Formation overlies the Bexar Shale Formation which overlies the Cow Creek Formation.  As indicated on Table 1-1, only those wells screened in a single formation are included when calculating the average water level in each formation.  Typically, the water levels measured at CSSA decrease from the Lower Glen Rose to the Bexar Shale Formation to the Cow Creek Formation.  The average groundwater elevations in December 2001 for the Lower Glen Rose, Bexar Shale, and Cow Creek formations were 1149.7 feet, 1131.4 feet, and 1125.6 feet, respectively.  The average groundwater elevations measured in the September 2001 event also decreased in elevation from the Lower Glen Rose to the Bexar Shale and to the Cow Creek Formation with average elevations of 1140.5 feet, 1098.2 feet and 1095.8 feet, respectively.  Evaluation of trends in water level elevations in the different formations will continue as additional wells are installed. 

2.0 BASEWIDE FLOW DIRECTION AND GRADIENT

    A groundwater potentiometric surface map generated from the December 2001 groundwater elevations is shown in Figure 2-1.  Among the cluster wells CS-MW6-LGR, CS-MW7-LGR, CS-MW8-LGR, CS-MW9-LGR, and CS-MW10-LGR, only the water level measurements from the Lower Glen Rose were used in creating the potentiometric surface map.  The December 2001 potentiometric surface map indicates a variety of flow directions.  The dominant groundwater gradient appears to be to the southeast at 0.0092 feet/feet.  Groundwater flow directions and gradients during past monitoring events are provided in Table 4 of the Introduction to the Quarterly Groundwater Monitoring Program (Parsons 2001) for comparison. 

    The overall observation from the December 2001 potentiometric surface map (Figure 2-1) is that CSSA wells exhibited a wide range of groundwater elevations.  The water level measurements suggest that groundwater elevations are somewhat higher in the central and northwestern portions of CSSA.  Overall, the groundwater elevations are generally lower towards the south with Well CS-1 having the lowest groundwater elevation of all measured wells. 

   There were exceptions to the general south-southeast decline in groundwater elevations.  Well CS-MW4-LGR in the central portion of CSSA had one of the highest groundwater elevations measured at 1170.0 feet above MSL.  At CS-MW4-LGR, the gradient appears to be toward the north and northwest and toward the south and southeast (Figure 2-1).  In the northwestern corner of CSSA, Well CS-H had a groundwater elevation measured at 1182.1 feet MSL which is the highest of the measured water levels.  In this localized area at the northwestern corner, the groundwater gradient appears to be to the northwest, toward off-post well FO-20. 

    The groundwater gradient presented in Figure 2-1 incorporates measured groundwater elevations from the Lower Glen Rose Formation only and those wells with open borehole completions (CS-1, CS-9, CS-10, CS-11, CS-D and CS-16).  In the area around Building 90, in the southwest corner of CSSA, potentiometric surface maps were created using December 2001 groundwater elevations from wells screened in the Lower Glen Rose and Cow Creek Formations (Figure 2-2 and Figure 2-3, respectively).  The Lower Glen Rose Formation potentiometric surface map indicates groundwater elevations decrease to the southwest, locally, at Building 90.  The Cow Creek Formation potentiometric surface map indicates that groundwater elevations decrease toward the north, locally, at Building 90 in December 2001.  The September 2001 event was the first event in which local potentiometric maps were prepared for the area around Building 90.  For December 2001, the groundwater elevations decreased to the southwest in the Lower Glen Rose Formation, a reversal from the flow direction to the north observed in September 2001.  The flow direction in the Cow Creek Formation appears to be the same in September and December 2001, with elevations decreasing toward the north. 

As shown in Figure 2-1, water levels at CSSA show much variability.  This variability is likely associated with various factors: 1) differences in well completion depths and formations penetrated; 2) differences in recharge rates due to increased secondary porosity associated with the Salado Creek floodplain; 3) differences in recharge rates due to increased secondary porosity associated with the fault zone; 4) unknown pumping rates from public and private water supply wells located off-post but near the CSSA boundary; and 5) locations of major faults or fractures.  Most potentiometric surface maps prepared for CSSA are based on water levels from wells with different completion depths, with the exception of Figure 2-2 and Figure 2-3.  Additional information concerning this issue is included in the Introduction to the Quarterly Groundwater Monitoring Program (Volume 5, Groundwater).  Because several wells depicted on Figure 2-1 are open to multiple water-bearing zones, potentiometric surface maps should be considered qualitatively.  The differences in water levels across CSSA may stem from differences in the various wells� completions.  Wells CS-D, CS-2, CS-4, CS-MW1-LGR and CS-MW2-LGR are open-hole completions in the Lower Glen Rose, or the Lower Glen Rose and the upper portion of the Bexar Shale.  Well CS-16 is open through the Lower Glen Rose, the Bexar Shale and the Cow Creek Formations.  Therefore, water level measurements obtained from some wells (i.e., CS-16 and CS-D) represent water levels measured from up to three different formations.  Wells completed in the Lower Glen Rose only represent the water level for that formation.  Interpretation of the data for the overall potentiometric surface map is complicated by these well completion differences.  As more wells are completed in the different formations, use of well data from wells screened through multiple formations can be reduced or eliminated in future water level and gradient determinations. 

3.0 WELL CS-16 WATER LEVEL AND TRANSDUCER DATA

    Precipitation data collected from the meteorological station at Well CS-16 between October 5, 1998, and December 21, 2001, are shown in Figure 3-1.  During the September 2001 monitoring event the water level data from the CS-16 transducer was not recorded due to a technical malfunction.  Therefore, CS-16 groundwater elevation data and precipitation data from the June 2001 event through the September 2001 monitoring event is missing from Figure 3-1.  The water level measured in Well CS-16 increased 28.21 feet from the September 2001 measured water level. 

    As noted earlier, groundwater levels increased 15.46 feet, as averaged from each formation, between September 13, 2001, and December 21, 2001.  During this period, there were 28 rainfall events with a total precipitation of 10.13 inches.  During the previous quarter when groundwater levels increased 23.16 feet, there were 17 rainfall events with a total precipitation of 14.73 inches.

4.0 DECEMBER 2001 ANALYTICAL RESULTS

    Groundwater sampling was performed December 10 through December 14, 2001.  Twenty-seven on-post wells were sampled using dedicated low-flow pumps: CS-1, CS-2, CS-9, CS-10, CS-11, CS-16, CS-D, CS-G, CS-H, CS-I, CS-MW1-LGR, CS-MW2-LGR, CS-MW3-LGR, CS-MW4-LGR, CS-MW5-LGR, CS-MW6-LGR, CS-MW6-BS, CS-MW6-CC, CS-MW7-LGR, CS-MW7-CC, CS-MW8-LGR, CS-MW8-CC, CS-MW9-LGR, CS-MW9-BS, CS-MW9-CC, CS-MW10-LGR, and CS-MW10-CC.  Wells G and H were sampled with a bailer during this sampling event.  Bladder pumps had not been installed in these wells as of December 2001.

    The analytical program for on-post wells includes metals, VOCs, anions and cations analysis only.  Samples from the high capacity water supply well CS-11 (currently offline) and newly installed wells CS-MW10-LGR and CS-MW10-CC were analyzed for the full VOC list.  Drinking water supply wells were analyzed for a reduced list of VOCs which was approved by EPA and TNRCC October 5, 1999.  The reduced list included bromodichloromethane, chloroform, dibromochloromethane, 1,1-dichloroethene, cis-1,2-dichloroethene, trans-1,2-dichloroethene, methylene chloride, tetrachloroethene, trichloroethene, and vinyl chloride.  For initial sampling at each newly installed monitoring well (CS-MW10-LGR and CS-MW10-CC) and well CS-11, groundwater was also tested for cations and anions during this sampling event. 

    The Parsons data package ID numbers DO5084-14, DO5084-15, DO5084-16, DO5084-18, DO5084-19, DO5084-22, and DO5084-23 contains the analytical results for this sampling event.  The data packages were received by Parsons from January 14 through 21, 2002, and subsequently validated and submitted to AFCEE from February 7 through February 23, 2002.  AFCEE approval of the various packages was received from March 8 through March 19, 2002.  All detected concentrations of metals and VOCs, as well as the cation and anion results, are presented in Table 4.  Full analytical results for December 2001 are presented in Appendix B.  Cumulative VOC and metals data from this round and all previous sampling events can be found in Tables 6 and 7, respectively, of the Introduction to the Quarterly Groundwater Monitoring Program (Parsons 2001). 

4.1 Volatile Organic Compound Analyses

    MCLs were exceeded in wells CS-16, CS-D, CS-MW1-LGR and CS-MW2-LGR in the December 2001 event.  For Well CS-16, the PCE concentration was 148.43 �g/L, the TCE concentration was 164.54 �g/L, and the cis-1,2-DCE concentration was 141.7 �g/L.  Chloroform and trans-1,2-DCE, have been sporadically detected in CS-16, and were detected at levels above the MDL but below the RL in December 2001.

    The results for the compounds PCE, TCE, and cis-1,2-DCE in CS-D were rejected because concentrations of these analytes were over the calibration range in the original undiluted analyses.  The samples were diluted and reanalyzed, but 11 days past the expiration of holding time.  Therefore, the results for these three analytes are flagged with an �R� and are unusable, except as screening data.  Concentrations reported with an �R� flag were PCE 130.14 �g/L, TCE 178.59 �g/L and cis-1,2-DCE 145.19 �g/L.  Well CS-D is not a drinking water supply well, and the well was not re-sampled.  Well CS-D had a trans-1,2-DCE concentration of 0.46 �g/L, chloroform was detected below the RL at 0.15 �g/L and methylene chloride was detected at 0.77 �g/L in the December 2001 event.  The field duplicate sample analyzed for CS-D reported trans-1,2-DCE at 0.43 �g/L, chloroform at 0.16 �g/L, and methylene chloride at 0.83 �g/L.  The field duplicate analyzed for CS-D was also �R� flagged for the compounds PCE, TCE, and cis-1,2-DCE. 

    The concentrations of PCE, TCE, cis-1,2-DCE, and trans-1,2-DCE in CS-MW1-LGR were 22.84 �g/L, 32.29 �g/L, 27.7 �g/L, and 0.23 �g/L, respectively.  The PCE and TCE MCLs were exceeded in CS-MW1-LGR. 

    PCE and TCE concentrations were also above the MCLs in CS-MW2-LGR at 10.6 �g/L and 8.94 �g/L, respectively.  A cis-1,2-DCE concentration of 3.95 �g/L was also detected as well as trans-1,2-DCE at 0.15 �g/L. 

   Wells CS-16 and CS-D reported concentrations above the MCL for the compounds PCE, TCE, and cis-1,2-DCE.  CS-MW1-LGR and CS-MW2-LGR reported concentrations above the MCL for the compounds PCE and TCE.  The concentration trends over time for these four wells and these compounds are shown in Figure 4-1, Figure 4-2, and Figure 4-3.  Trends over time in well CS-16 show variation in concentrations with generally stable trends or averages in the last two years of monitoring.  Concentrations in well CS-D are generally increasing over time.  Wells CS-MW1-LGR and CS-MW2-LGR have been monitored for less time than wells CS-16 or CS-D, and both trend graphs show increases in concentrations over the last year of monitoring.  Screening data from Well CS-D are included on the figures to enable comparison of concentration trends over time. 

    Two monitoring wells, CS-MW10-LGR and CS-MW10-CC, completed in October 2001 were sampled for the first time in December 2001.  No VOC analytes were detected in CS-MW10-CC; however, CS-MW10-LGR did have a chloroform detection of 0.1 mg/L, a PCE concentration above the RL of 2.5 mg/L, and a TCE concentration of 0.51 mg/L, above the MDL. 

    CS-MW5-LGR had three VOC analytes detected.  PCE was detected at a concentration of 1.02 �g/L, which is below the RL.  TCE was detected at 2.22 �g/L and cis-1,2-DCE was detected at 2.25 �g/L.  There was a slight increase in the concentrations of TCE and cis-1,2-DCE, and a decrease in the PCE concentration since CS-MW5-LGR was initially sampled in June 2001. 

   Well CS-2 had a sub-RL PCE concentration of 0.35 �g/L and TCE at 0.17 �g/L.  PCE concentrations in this well were slightly higher than previous levels. 

CS-MW4-LGR had one sub-RL VOC detection for cis-1,2-DCE at 0.12 �g/L.  This is the first VOC analyte detected in this well since sampling began in June 2001. 

 CS-MW8-LGR had a detection of PCE at a concentration of 0.62 �g/L, which is below the RL.  This result is consistent with concentrations detected since the well was initially sampled in June 2001. 

    The water supply wells, CS-1, CS-9, and CS-10, did not have any VOC concentrations detected above the RL.  Off-post Well CS-1 had a sub-RL TCE detection at 0.20 �g/L that was a decrease from the September 2001 level of 0.29 �g/L.  PCE was not detected in CS-9 and CS-10 during this monitoring event after being detected for the first time in these wells in March 2001.  Well CS-10 had one VOC analyte detected, chloroform at a concentration of 0.38 �g/L, which is significantly below its MCL of 100 �g/L.  This chloroform concentration is an increase from previous levels of chloroform detected since March 2000.  Well CS-9 had no VOC analytes detected.  Well CS-11 (a former drinking water well) had one cis-1,2-DCE detection at a concentration of 0.3 �g/L. 

    Wells CS-I, CS-H, CS-MW6-LGR, CS-MW6-BS, CS-MW6-CC, CS-MW8-CC, and CS-MW9-LGR had no VOC analytes detected above either the MDL or RL.  Wells CS-G, CS-MW3-LGR, CS-MW7-LGR, CS-MW7-CC, CS-MW9-BS, and CS-MW9-CC reported sub-RL methylene chloride concentrations.  Methylene chloride has been reported in samples from on- and off-post wells since 1992.  However, each time methylene chloride has been detected in a sample, it has also been consistently present in the analysis method blank, indicating the likelihood that this analyte was introduced as a laboratory contaminant and is not present in the groundwater.  There are no known historical uses of methylene chloride on-post. 

4.2 Metals Analyses

    Of the nine metals regularly analyzed for at CSSA, lead, copper and iron do not have an MCL established by the EPA.  An action level (AL) for a treatment technique to control corrosiveness of water is defined by the EPA to be 1.3 mg/L for copper and 0.015 mg/L for lead.  An additional guidance set by the EPA for iron is a secondary standard for iron of 0.3 mg/L. 

    No on-post drinking water wells had detections of metals above the appropriate MCL, AL, or secondary standard in the December 2001 sampling event.  However, lead and iron were detected above the appropriate AL in two on-post monitoring wells.  Lead was detected above the AL (0.015 mg/L) at a concentration of 0.0827 mg/L in Well CS-I.  This concentration is greater than the September 2001 event, which reported a concentration of 0.0193 mg/L.  Iron was reported above the secondary standard (0.3 mg/L) at a concentration of 1.004 mg/L in Well CS-11.  No other CSSA wells exhibited metals levels that surpassed the MCLs/ALs during this monitoring event. 

4.3 Cations and Anions Analyses

     Samples collected from two newly installed CSSA monitoring wells CS-MW10-LGR and CS-MW10-CC and a sample from CS-11 (a former drinking water supply well) were analyzed for cations and anions in the December 2001 event.  This data is presented in Appendix B.  Evaluation of the cation and anion data from all new monitoring wells; however, will be initiated after a sufficient number of wells are screened in each formation to evaluate whether differentiation or trends can be identified.  A future groundwater monitoring report and or Conceptual Site Model will include a detailed evaluation and data summary after sufficient data have been collected.

5.0 SUMMARY

 Appendix A
Evaluation of Data Quality Objectives Attainment