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March 2005 Off-Post Quarterly Groundwater Monitoring Report

Section 3 - Analytical Results

Twenty-one wells contained VOCs at concentrations above the MDL in March 2005. Based on historical detections, the lateral extent of VOC contamination extends approximately 0.5 mile beyond the south and west boundaries of CSSA to well I10‑7 to the west and LS‑4 to the south. Information such as well depth, pump depth, and other pertinent data necessary to properly characterize the vertical extent of migration, is not readily available from most well owners. For the purposes of this report, the concentrations of PCE, TCE, and cis-1,2-DCE are the only VOCs presented in summary tables in Section 3.1 through 3.8, as these are the most common COCs detected. Other VOCs, if detected, are discussed in the text and presented in Appendix B.

Off-post wells are grouped by community or neighborhood for the following discussion of the March 2005 results. Concentrations of VOCs detected in March 2005 are presented in Table 3.1. Full analytical results from the March 2005 sampling event are presented in Appendix B. PCE, TCE, and cis-1,2-DCE concentration trends are illustrated in Figure 3.1 for wells LS‑2, LS‑3, LS‑6, LS‑7, OFR‑3, RFR‑10, and RFR‑11. These wells were selected for display because they have had detections of PCE and TCE that approach and/or exceed MCLs. Figure 3.1 also includes precipitation data from the CS‑MW16‑LGR weather station and the AOC‑65 weather station. These figures are presented prior to the discussion of March 2005 groundwater sampling results for each neighborhood. Appendix C is a comparison of pre- and post-GAC PCE and TCE concentrations.

Further discussion of the quarterly groundwater monitoring program conducted from June 2001 to March 2005 is available in previous quarterly reports, located in Volume 5, Groundwater of the CSSA Environmental Encyclopedia.

Methylene chloride has been periodically detected in on- and off-post samples since 1992. However, because methylene chloride was also detected in associated quality control samples, it was concluded the analyte was introduced as a laboratory contaminant and was not present in the groundwater. In addition, there are no known historical uses of methylene chloride on-post, and methylene chloride has not been detected in the same wells consistently over time, supporting the conclusion that methylene chloride is present because of laboratory procedures. The earliest detection of methylene chloride was in November 1992, with sporadic detections in September 1999, December 2001, March 2002, and September 2002. Three detections of methylene chloride reported in March 2003 were flagged with a �B� flag, as the concentration of methylene chloride was above the RL in the method blank. Methylene chloride was not detected in the June 2003, September 2003, December 2003, March 2004, or June 2004 sampling events. In September 2004 methylene chloride was detected in two wells. In December 2004 methylene chloride was detected in one sample (OFR-2) along with its field duplicate; however, the results were rejected during data verification due to the fact that the parent sample and field duplicate were not analyzed back to back. There was a non-compliant instrument continuing calibration verification injection which affected the field duplicate, but not the parent sample. These data were �R� flagged. In March 2005 methylene chloride was not detected in any normal samples submitted, but was present in a trip blank, reinforcing the presence of methylene chloride as a laboratory contaminant.

Chloroform has been detected on-and off-post since 1992. Chloroform is regulated by the EPA as a total trihalomethane (TTM) with a combined MCL of 80 ppb for all TTMs detected. No detections of chloroform and other TTMs have been above the combined MCL. These compounds are regulated as byproducts related to drinking water disinfection. Chloroform detections in well JW-14 are related to the well owner adding household bleach to the drinking water well for disinfection. In December 2004 the TTMs in well RFR-13 were approaching the combined MCL of 80 ppb. The well owner was contacted and an additional sample was collected January 11, 2005. The combined TTMs increased but remained below the MCL. According to the well owner the well was treated with bleach for disinfection purposes after installation. The well owner was informed of the results and provided TCEQ guidance documents informing the public about well disinfection and proper purging techniques following home disinfection. March 2005 TTMs results for well RFR-13 are provided in Section 3.8.

3.1 - Dominion

March 2005 Results

One well (DOM-2) in the Dominion subdivision was sampled in March 2005. DOM-2 reported toluene at 0.15 �g/L, below the RL.

Results Summary

DOM-2 has been sampled yearly since September 2001. No VOCs of concern have been detected in this well. DOM-2 will remain on the annual sampling schedule in accordance with the DQOs.

3.2 - Fair Oaks

March 2005 Results

Two wells (FO-J1 and FO-8) in the Fair Oaks area were sampled in March 2005. FO-J1 reported PCE at a concentration of 0.12 �g/L, TCE at 0.25 �g/L, and cis-1,2-DCE at 0.53 �g/L, all below the RL.

Well FO-8 had no VOC detections in the March 2005 sampling event. Well FO-8 is sampled on a yearly schedule in accordance with DQOs. PCE and TCE have never been detected in this well.

Results Summary

Wells in the Fair Oaks area were first sampled in September 2001. Through March 2005 Fourteen quarterly samples were collected from FO-J1. PCE levels have ranged from non-detects to 0.36 �g/L (December 2004). FO-J1 will remain on the quarterly sampling schedule for upcoming events. Well FO-8 has been sampled yearly since March 2002 and will remain on an annual sampling schedule or be sampled as needed in accordance with DQOs. Results for PCE, TCE, and cis-1,2-DCE from wells sampled in the Fair Oaks area during the 2005 sampling events are provided in the following table:

3.3 - Hidden Springs Estates

March 2005 Results

In March 2005, Hidden Springs Estates well HS-1 was to be sampled. However, because HS-1 is currently inoperable HS-2 was sampled instead. PCE was detected at a concentration of 0.17 �g/L. This concentration was above the MDL, but below the RL. Based on historical detections, HS-2 will remain on the quarterly sampling schedule in accordance with the project DQOs.

Results Summary

Wells in Hidden Springs Estates were first included in CSSA�s groundwater monitoring program in December 2001. Over the history of the sampling at well HS-2, PCE levels have ranged from 0.11 to 0.23 �g/L. The 2005 results for PCE, TCE, and cis-1,2-DCE from HS-2 are provided below:

3.4 - Interstate I-10 Area

March 2005 Results

Three wells in the I-10 area were sampled in March 2005 (I10-2, I10-4, and I10-7). PCE and TCE were detected in well I10-2, both at a concentration of 0.12 �g/L. Wells I10-4 and I10‑7 reported no VOC detections. Based on historical detections, I10-2 and I10-4 will remain on the quarterly sampling schedule. Well I10-7 will also remain on a quarterly sampling schedule as a plume delineation well.

Results Summary

Wells in the I-10 area were first included in CSSA�s groundwater monitoring program in September 2001. PCE levels in I10-2 have ranged from 0.06 to 0.16 �g/L, and in I10-4 from 0.06 to 2.22 �g/L. Results for PCE, TCE, and cis-1,2-DCE from I-10 area wells sampled during the 2005 sampling events are provided in the following table:

3.5 - Jackson Woods

March 2005 Results

In March 2005, eight Jackson Woods Subdivision wells (JW‑7, JW‑8, JW‑9, JW‑12, JW‑14, JW‑28, JW‑29, and JW‑30) were sampled. Four of the eight wells sampled, JW‑7, JW‑8, JW‑14, and JW‑30, had detections of contaminants of concern below the applicable MCLs. Wells JW‑9, JW-12, JW-28, and JW‑29 had no VOC detections. Wells JW‑7, JW‑8, JW‑14, JW‑28, and JW‑30 will continue to be monitored on a quarterly basis because of previous detections. Well JW‑29 had no detections the last six quarters but will remain on the quarterly sampling schedule due to its location.

Well JW‑7 was initially sampled in September 2003. The March 2005 sampling event was the seventh consecutive round of sampling at JW-7. PCE and dichlorodifluoromethane were detected at concentrations of 0.38 �g/L and 0.33 �g/L, respectively. PCE concentrations in this well have ranged from 0.42 to 0.65 �g/L.

Well JW‑8 reported PCE (0.12 �g/L), TCE (0.21 �g/L), and cis-1,2-DCE (0.37 �g/L) in March 2005. TCE and cis-1,2-DCE were not detected in this well until December 2004. PCE levels have ranged between 0.29 to 0.35 �g/L.

PCE (0.10 �g/L) was detected in the JW‑14 field duplicate and chloroform (0.14 �g/L) was detected in the JW‑14 normal sample and field duplicate. Chloroform has been consistently detected in this well since September 2001 ranging from 0.03 to 53.45 �g/L. All chloroform results have been below the TTMs MCL of 80 mg/L. The well owner routinely disinfects this well with household bleach causing TTM to be detected. PCE was last detected in this well in December 2004, all PCE detections have been below the RL.

No VOCs were detected in well JW‑29. Well JW‑29 had a PCE detection in June 2003. Although this well has had seven consecutive sampling events with no VOC detections it will remain on the quarterly sampling schedule because it is near impacted wells.

JW‑30 reported detections of PCE (0.10 �g/L), TCE (0.23 �g/L), cis-1,2‑DCE (0.42 �g/L), and chloroform (0.11 �g/L) in March 2005. PCE levels have ranged from 0.06 �g/L to 0.2 �g/L, all below the RL. Only one other detection of TCE and cis-1,2-DCE were reported in March 2003, both below the RL.

Wells JW‑9, JW‑12, JW-28, JW-28 field duplicate, and JW‑29 had no VOC detections in March 2005. Wells JW‑7, JW‑8, JW‑14, JW‑28, JW‑29, and JW‑30 will remain on the quarterly sampling schedule in accordance with the Plan.

Results Summary

Off-post sampling was first performed in the Jackson Woods area in 1995 with sampling at JW‑30. No VOCs were detected in this well at that time. JW‑30 was again sampled in September 1999, and methylene chloride was the only VOC detected. Additional Jackson Woods Subdivision wells have been added to the sampling list since 1995. Results for PCE, TCE, and cis‑1,2‑DCE in wells in the Jackson Woods area sampled during the 2005 sampling events are provided below:

3.6 Leon Springs Villa

March 2005 Results

Six wells (LS‑2, LS‑3, LS‑4, LS‑5, LS‑6, and LS‑7) in the Leon Springs Villa subdivision were sampled in March 2005. All wells had detections below the applicable MCLs.

Well LS‑2 had detections of PCE and TCE at concentrations of 2.25 mg/L and 0.40 mg/L, respectively, in March 2005. The TCE concentration was above the MDL and below the RL, while the PCE concentration was above the RL and below the MCL. An evaluation of concentration trends through the March 2005 event for LS‑2 is given in Figure 3.1. PCE concentrations doubled from September to December 2002. From December 2002 to March 2004 PCE levels had been decreasing and had fallen below the RL. In June 2004 PCE levels were slightly above the RL. TCE concentrations have remained fairly stable since August 2001, with a slight increase from September to December 2002.

Results for LS‑3 included concentrations of PCE at 1.74 mg/L and TCE at 0.19 mg/L. TCE was below the RL while PCE was above the RL and below the MCL. An evaluation of concentration trends through March 2005 in well LS‑3 is given in Figure 3.1. Based on previous detections, CSSA installed a combined GAC filtration system on wells LS‑2 and LS‑3 in April 2002. Post GAC samples were collected in March 2005. One sample (A-1) was collected from between the carbon canisters and one sample (A-2) was collected after both carbon canisters. Sample A-1 found low levels of VOCs; 0.74 mg/L and 0.33F mg/L for PCE and TCE, respectively. Sample A-2 found no VOCs. See Appendix C for analytical results. Wells LS‑2 and LS‑3 should continue to be sampled quarterly in the future.

In March 2005, PCE was detected at a concentration of 0.18 mg/L in LS‑4, below the RL. Well LS‑4 should continue to be sampled quarterly based on VOC detections ranging from 0.06 to 0.25 mg/L.

Well LS‑5 had a detection of TCE at a concentration of 0.17 mg/L in March 2005. The field duplicate reported a similar result with a TCE concentration of 0.21 mg/L. Previous concentrations have all been above the MDL and below the RL and MCL for both PCE and TCE. TCE has been consistently detected in this well, at concentrations below the RL ranging from 0.16 to 0.51 �g/L. The residence supplied by LS-5 has recently been occupied and water production from this well will likely increase. Well LS‑5 should remain on the quarterly sampling schedule.

In March 2005, PCE, TCE, and naphthalene were detected at concentrations of 4.22 mg/L, 0.41 mg/L, and 0.43 mg/L respectively, in LS‑6. PCE and naphthalene were above the RL but below the MCL while TCE concentrations were below the RL. An evaluation of concentration trends in LS‑6 through March 2005 is provided in Figure 3.1. Well LS‑6 is equipped with a GAC treatment system because concentrations exceeded the MCL in the past. Post GAC samples were collected this quarter and no VOC were reported in the LS-6 post GAC sample, see Appendix C for results. Well LS‑6 should continue to be sampled on a quarterly schedule.

The LS‑7 sample contained concentrations of PCE (2.32 mg/L) and TCE (0.31 mg/L) during the March sampling event. TCE was below the RL, as shown by the concentration trends presented in Figure 3.1. PCE was below the MCL and above the RL. Well LS‑7 was equipped with a GAC treatment system when previous detections approached the MCL. Post GAC samples were collected this quarter and no VOC were reported in the LS-7 post GAC sample, see Appendix C for results. Well LS‑7 should continue to be sampled on a quarterly schedule.

Results Summary

Wells from the Leon Springs Villa area were first sampled in December 1999 to determine whether VOCs had migrated off-post to the south of CSSA. Based on past results for VOCs, CSSA installed GAC treatment systems at wells LS‑2/LS‑3, LS‑6, and LS‑7. In March 2005, semi-annual post‑GAC confirmation samples were collected from all Leon Springs wells equipped with GAC systems (Appendix C). The samples confirm that the GAC units are working effectively and that VOCs are reduced to concentrations below the applicable drinking water MCLs. Chloroform was detected in post-GAC samples from LS‑2/LS‑3 at concentrations below the RL and MCL in September 2002, March 2003, September 2003, March 2004, September 2004 and again in March 2005. In March 2005, PCE and TCE were detected below the RL, in sample LS-2/LS‑3‑A1. Sample port A1 is located between the GAC canisters. Sample port A2 is located after both carbon canisters and is a representative sample of the water being supplied to homeowners. Sample LS‑2/LS‑3‑A2 had a detection of chloroform at 0.10 mg/L, below the RL. The next post-GAC sampling event will be conducted in September 2005.

Results for PCE, TCE, and cis-1,2-DCE in pre-GAC samples collected from the Leon Springs Villa community wells during 2005 are provided below:

3.7 - Old Fredericksburg Road Area

March 2005 Results

Four wells (OFR‑1, OFR‑2, OFR‑3, and OFR-4) along Old Fredericksburg Road were sampled in March 2005. OFR‑1 and OFR‑3 had detections of VOCs.

In March 2005, PCE was detected at 0.19 mg/L, in well OFR‑1, which is below the RL. The results for OFR‑2 and OFR-4 showed no VOCs present in the sample. Over the history of sampling at these wells, PCE has ranged from 0.29 to 0.49 �g/L in OFR-1 and 0.005 to 0.35 �g/L in OFR-2. These wells should continue to be monitored quarterly in accordance with the Plan. No trend analysis was prepared for these wells because detections have been well below the MCL.

In March 2005, OFR‑3 had detections of PCE (1.35 mg/L), TCE (2.08 mg/L), and dichlorodifluoromethane (0.16 mg/L). PCE and dichlorodifluoromethane concentrations were above the MDL but below the RL, while TCE was above the RL but below the MCL. In April 2002, a GAC unit was installed on OFR-3 based on PCE concentrations. An evaluation of concentration trends in well OFR-3 through March 2005 is provided in Figure 3.1. Increases in PCE and TCE occurred from February to March 2002. PCE and TCE decreased from June 2002 to September 2002 and remained stable until June 2003. The December 2003 event showed a significant increase in the PCE and TCE concentrations and both COCs exceeded their MCLs. In March 2004 concentrations decreased to below the applicable MCLs but again in June 2004 they exceeded the MCL. Well OFR‑3 should continue to be sampled on a quarterly schedule.

Results Summary

Well OFR‑2 was first sampled in December 1995 to determine whether VOCs had migrated off-post to the west of CSSA. Every six months, post-GAC samples are collected to confirm the GAC filtration system at OFR‑3 is working. To date, no VOCs have been detected above RLs in the post-GAC samples. The next post-GAC confirmation sample for OFR‑3 will be collected in September 2005 and results for previous post-GAC sampling events are given in Appendix C. Results for PCE, TCE, and cis-1,2-DCE from Old Fredericksburg Road area wells sampled during the 2005 events are provided below:

3.8 - Ralph Fair Road Area

March 2005 Results

In March 2005, six wells (RFR‑4, RFR‑5, RFR‑10, RFR‑11, RFR‑12, and RFR‑13) in the Ralph Fair Road area were sampled. Of the seven wells sampled, one well (RFR‑10) had detections greater than the MCL.

Well RFR-4 had a detection of chloroform (0.22 mg/L) in March 2005. This well has been sampled annually since March 2004. It will remain on an annual sampling schedule in accordance with the DQOs. Well RFR-5 had no VOC detections and will remain on the annual sampling schedule.

Well RFR‑10 concentrations exceeded the MCLs for PCE at 8.03 mg/L and TCE exceeded the MCL at a concentration of 5.19 mg/L. Cis-1,2-DCE was also detected below the RL at a concentration of 0.43 mg/L. An evaluation of concentration trends through March 2005 is included in Figure 3.1. A GAC filtration system was installed on RFR‑10 when concentrations exceeded the MCL. Well RFR‑10 should continue to be sampled on a quarterly schedule.

In March 2005, RFR‑11 had detections of PCE (4.84 mg/L) and TCE (0.32 mg/L), both of which were below MCL. Based on previous results, RFR‑11 should continue to be sampled on a quarterly schedule. Over the sampling history of this well, PCE and TCE have ranged from 0.89 to 16.73 �g/L and 0.12 to 1.73 �g/L, respectively.

In March 2005, Well RFR‑12 had a detection of TCE at a concentration of 0.20 �g/L, which is below the RL. Well RFR‑12 will remain on the quarterly sampling schedule in accordance with the Plan.

Well RFR‑13 is a newly installed drinking water well. Bromodichloromethane (1.47 mg/L), bromoform (1.21 mg/L), chloroform (17.38 mg/L), and dibromochloromethane (1.52 mg/L) were detected in this well. These chloroform results are below the TTMs MCL of 80 mg/L and have decreased since the sample collected January 2005. The well owner informed Parsons that the well was treated with household bleach at installation for disinfection purposes.

Results Summary

Ralph Fair Road wells RFR‑3 and RFR‑8 were sampled during the first off-post sampling performed in 1995. Wells RFR‑10 and RFR‑11 required installation of GAC filtration systems in October 2001 when concentrations exceeded the MCL. Post-GAC sampling confirms that the GAC filtration systems are working effectively. See Appendix C for the March 2005 and previous post‑GAC sampling results. Post-GAC confirmation samples will be collected again in September 2005. Results in 2005 for wells in the Ralph Fair Road area are provided below:

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