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March 2003 Off-Post Quarterly Groundwater Monitoring Report

Section 3 - March 2003 Groundwater Monitoring Analytical Results

Overview of March 2003 Event

Twenty-two wells contained VOCs at concentrations above the MDL in March 2003. Based on historical detections, the lateral extent of VOC contamination extends approximately 0.5 miles beyond the south and west boundaries of CSSA to well I10-4 to the west and LS-4 to the south. The vertical extent of migration cannot be determined because information regarding well completion depths is not available for wells sampled. Information providing depth of wells, pump depth, and other pertinent data necessary to properly characterize the vertical extent of migration is not readily available from the well owners.

Off-post wells are grouped by community or neighborhood for a discussion of the March 2003 results. Concentrations of VOCs detected in March 2003 are presented in Table 3.1. Full analytical results from the March 2003 sampling event are presented in Appendix B. PCE, TCE, and cis-1,2-dichloroethene (cis-1,2-DCE) concentration trends are illustrated for wells with detections of PCE and TCE that approach or exceed the MCL (Figure 3.1 [LS-2], Figure 3.2 [LS-3], Figure 3.3 [LS‑6], Figure 3.4 [LS-7], Figure 3.5 [OFR-3], Figure 3.6 [RFR-10], and Figure 3.7 [RFR‑11]). Figures 3.1 to 3.7 also include precipitation data from the Well CS-MW16-LGR weather station, for evaluation of the effects of precipitation on concentrations, if any. These figures are presented after the discussion of March 2003 groundwater sampling results for each neighborhood presented below. A table summarizing the 2003 detections of COCs for wells in each neighborhood is included in the results sections, below. Appendix C is a comparison of pre- and post-GAC concentrations detected in wells for PCE and TCE. No detections of PCE and/or TCE above the applicable MCL have occurred in the post-GAC samples collected. Further discussion of the off-post quarterly monitoring program conducted from September 2001 through December 2002 is available in the Annual Groundwater Monitoring Report, (Parsons, 2003, currently draft) and/or December 2002 Off-Post Groundwater Report (Parsons, 2003), located in Volume 5, Groundwater of the CSSA Environmental Encyclopedia.

Methylene chloride has been reported on- and off-post since 1992. However, each time methylene chloride was detected in a sample, it was also present in associated quality control samples, indicating a high likelihood that this 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 due to 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. Some detections of methylene chloride reported in March 2003 were flagged with a �B� flag, indicating the analyte was found in an associated blank, as well as in the normal sample. Additional details are given in the results sections, below.

During the March 2003 sampling event, toluene was detected in 11 off-post wells at concentrations ranging from 0.07 �g/L to 2.37 �g/L. Although all of these concentrations are well below the MCL of 1,000 �g/L, the possible source of this contamination was researched since toluene has not previously been detected at comparable levels during CSSA�s groundwater monitoring program. Due to the sporadic low-level detections, a source associated with the sampling or analysis methodology was suspected. Toluene is a clear, colorless liquid with a distinctive smell. It is a gasoline-additive and it occurs naturally in crude oil. Toluene is also used in making paints, paint thinners, fingernail polish, lacquers, adhesives, and rubber and in some printing and leather tanning processes. A new adhesive tape was used to secure the sample labels to the sample bottles for the March 2003 event, and a strong odor was noted by the field personnel. Therefore, the tape was identified as a possible source. A sample of the tape was submitted to DHL Laboratory in Round Rock, Texas for analysis. A piece of tape was allowed to soak in water overnight, and the resulting water was found to contain over 1,000,000 �g/L toluene. Therefore, it is suspected that the low-level concentrations in the March 2003 groundwater samples were introduced by volatilization of toluene on the tape and adsorption into the samples during transit from the field to the laboratory.

3.1 - Dominion

One well in the Dominion area (DOM-2) has been sampled for three events, September 2001, March 2002 and March 2003. No VOCs were detected above the RL in March 2003. No PCE or TCE has been detected in DOM-2.

3.2 - Fair Oaks

March 2003 Results

In March 2003, three wells were sampled in the Fair Oaks area: FO-J1, FO-8, and FO‑17. Toluene was detected in all three wells in this sampling event, and cis-1,2-DCE and methylene chloride were detected in FO-J1. This was the seventh consecutive quarterly sample collected from FO-J1 and the second sample collected from FO-17 and FO-8 since March 2002. FO-J1 will remain on the quarterly sampling schedule for upcoming events. After a minimum of one year, the sampling frequency will be reviewed and possibly decreased in accordance with the off-post monitoring plan.

Results Summary

Wells in the Fair Oaks area were first sampled in September 2001. Results for PCE, TCE, and cis-1,2-DCE from wells sampled in the Fair Oaks area in the March 2003 sampling event are provided below.

The cumulative history of VOC sampling of groundwater at Hidden Springs for HS-2 can be found in Volume 5, Table 8, CSSA Environmental Encyclopedia.

3.4 - I-10 Area

March 2003 Results

In March 2003 three wells were sampled in the I-10 area: I10-2, I10-4, and I10-7. One sample (I10-7-NP) was also collected from a sink inside the I10-7 business; the sample was not purged prior to collection. I10-2 had VOC detections for PCE and TCE at concentrations of 0.10 mg/L and 0.06 mg/L, respectively. Based on these results, I10-2 will continue to be monitored on a quarterly basis in accordance with the plan. No VOCs were detected in I10-4, I10-7, or I10‑7‑NP in March 2003. This is the fifth consecutive sampling event with no VOCs detected in well I10-4, other than previous detections of methylene chloride. Therefore, I10-4 may be removed from the quarterly sampling schedule in the future. I10-7 was sampled in March 2003 for the second time since March 2002. As no detections of VOCs occurred in this sampling event, I10-7 can be sampled on an as needed basis in the future.

Results Summary

Wells in the I-10 area were first included in CSSA�s groundwater monitoring program in September 2001. TCEQ also collected split samples from I10-4 and sampled I10-5 in December 2001. Results for PCE, TCE, and cis-1,2-DCE from for I-10 area wells sampled in the March 2003 sampling event are provided below.

The cumulative history of VOC sampling of groundwater for wells along the I-10 area can be found in Volume 5, Table 8, CSSA Environmental Encyclopedia.

3.5 - Jackson Woods

March 2003 Results

In March 2003, four Jackson Woods wells (JW-9, JW-14, JW-26, and JW‑30) were sampled. An additional sample was collected from a sink inside the residence; the sample was not purged prior to collection. Toluene was detected in JW-9 at a concentration of 0.23 �g/L. As described previously, toluene is believed to be associated with tape used to secure sample labels to the bottles. JW-9 reported no other VOC detections for the fifth consecutive sampling event and can be sampled on an as needed basis in accordance with the Plan.

The well owner at JW-9 installed a filtration system before the December 2002 sampling event. No VOCs were detected in the post-filtration sample collected in December 2002. PCE (0.15 �g/L), chloroform (0.39 �g/L), and toluene (0.45 �g/L) were detected in JW-14. Chloroform has been consistently reported in this well since September 2001 and all results have been below the MCL of 80 mg/L. The non-purged sample (JW-14-NP) collected from inside the residence at well JW-14 also had detections of PCE (0.15 �g/L), chloroform (0.56 �g/L), methylene chloride (3.41 �g/L), and toluene (2.37 �g/L). JW-14 will remain on the quarterly sampling schedule in accordance with the Plan. JW-26 had detections of PCE (0.11 �g/L), naphthalene (0.07M �g/L), and dichlorodifluoromethane (0.11M �g/L). This is the first detection of PCE in well JW-26 since sampling began in March 2002. JW-26 will remain on the quarterly sampling schedule in accordance with the Plan. JW-30 had detections of TCE (0.08 �g/L) and cis-1,2-DCE (0.30 �g/L). JW-30 was sampled for the first time in December 1995 and then again in September 1999 and methylene chloride as the only previous VOC detection. JW-30 will remain on the quarterly sampling schedule in accordance with project DQOs.

Results Summary

Off-post sampling was first performed in the Jackson Woods area in 1995 and no VOCs were detected in the well (JW-30) sampled at that time. JW-30 was again sampled in September 1999, and methylene chloride was the only VOC detected. In March 2002, a new Jackson Woods well, JW-26, was sampled and chloroform (0.11 mg/L) and methylene chloride (0.21 mg/L) were detected in this well. Results for PCE, TCE, and cis-1,2-DCE from wells in the Jackson Woods community sampled in the March 2003 sampling event are provided below.

In June 2002, JW-9 had an �M� flagged result for 1,3,5-trimethylbenzene because the analyte was recovered slightly above tolerance in associated quality control samples. Also in June 2002, chloroform was detected in JW-14 at a concentration of 0.49 mg/L. In September 2002 and March 2003, chloroform was detected in JW-14 at a concentration of 0.24 mg/L and 0.30 mg/L, respectively. These detections are below the MCL for chloroform of 80 �g/L.

The cumulative summaries of VOC results from Jackson Woods wells can be found in Volume 5, Table 8, CSSA Environmental Encyclopedia.

3.6 - Leon Springs Villa

March 2003 Results

In March 2003, seven wells (LS-1, LS-2, LS-3, LS-4, LS-5, LS-6, and LS-7) were sampled in the Leon Springs Villa subdivision. PCE was detected in LS-1 at 0.46 mg/L and TCE at 0.12 mg/L. LS-1 also had detections of chloroform at 0.42 mg/L, the seventh consecutive detection for chloroform in this well, bromodichloromethane (0.46 mg/L), bromoform (0.58 mg/L), and dibromochloromethane (0.51 mg/L). All detections of chloroform have been above the MDL but below the MCL (80 mg/L) for chloroform.

LS-2 had detections of PCE and TCE, at concentrations of 4.25 mg/L and 0.30 mg/L, respectively in March 2003. PCE concentrations were above the RL and below the MCL. The TCE detection was above the MDL and below the RL and MCL. An evaluation of concentration trends through March 2003 for LS-2 is given in Figure 3.1. PCE concentrations varied from August 2001 to September 2002 and doubled from September to December 2002. From December 2002 to March 2003 PCE levels have dropped back below the MCL. TCE concentrations have remained stable since August 2001, with a slight increase from September to December 2002.

Results for LS-3 included concentrations of PCE at 3.99 mg/L, TCE at 0.35 mg/L, toluene at 0.35 �g/L, and chloroform at 0.12 mg/L. TCE, toluene, and chloroform were above the MDL but below the RL and MCL while PCE was above the MDL and RL but below the MCL. An evaluation of concentration trends through March 2003 in well LS-3 is given in Figure 3.2. The PCE concentration in LS-3 was 4.8 mg/L in September 2001, and remained above the RL (1.4 mg/L) until January 2002. PCE concentrations then increased significantly from June 2002 to December 2002, increasing from 1.06 mg/L to 4.42 mg/L. Wells LS-2 and LS-3 had a combined GAC filtration system installed by CSSA in April 2002, as described in the results section below. LS‑2 and LS-3 should be sampled quarterly in the future.

In March 2003, PCE was detected at a concentration of 0.25 mg/L in LS-4. No concentration trends are provided for LS-4 as no VOCs have been detected above the RL in this well. LS-4 should continue to be sampled quarterly due to VOCs detected above the MDL.

LS-5 had a TCE (0.19 mg/L) detection in this event. The concentration was above the MDL and below the RL and MCL. LS-5 should remain on the quarterly sampling schedule in accordance with the DQOs.

In March 2003, PCE, TCE and toluene were detected at concentrations of 4.19 mg/L, 0.21 mg/L, and 0.17 mg/L, respectively, in LS-6. An evaluation of concentration trends in LS‑6 through March 2003 is provided in Figure 3.3. After the maximum detection of 10.0 mg/L in September 2001, PCE concentrations remained between 1.5 and 3.0 mg/L from December 2001 to September 2002. The December 2002 concentration for PCE exceeded the MCL (5.0 mg/L) again at 6.86 mg/L, while TCE remained below the RL and MCL. In March 2003 PCE concentrations dropped back below the MCL. LS-6 is equipped with a GAC treatment system due to past VOC concentrations. Results of post-GAC sampling are discussed below. LS-6 should continue to be sampled on a quarterly schedule.

The LS-7 sample had concentrations of PCE (4.01 mg/L) and TCE (0.41 mg/L) during this event. An additional sample (LS-7-NP) was collected from a sink inside the residence; the sample was collected without purging the line. Sample LS-7-NP had a detection of toluene at a concentration of 0.78 mg/L. As described previously, toluene is believed to be associated with tape used to secure sample labels to the bottles. As shown by the concentration trends presented in Figure 3.4, PCE concentrations reported in March 2003 have decreased to below the MCL. PCE concentrations were between 1.1 mg/L and 4.6 mg/L for three years, from December 1999 through September 2002. From September 2002 to December 2002, PCE increased from 2.41 mg/L to 7.16 mg/L. The December 2002 PCE concentration was the first exceedance of the MCL (5.0 mg/L) in LS-7. 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 southwest of CSSA. Based on past concentrations of VOCs, CSSA installed GAC treatment systems at wells LS-2/LS-3, LS-6, and LS-7. Semi-annual post-GAC confirmation samples have been collected from all Leon Springs wells equipped with GAC systems (Appendix C). The testing has confirmed that the GACs are working effectively and that VOCs are reduced to below the applicable drinking water MCLs. However, in December 2002, it was noted that the GAC valves of RFR-11 had been adjusted so that water bypassed the GAC system. The valves were corrected prior to sampling and they were locked to prevent future bypassing of the GAC. The next post-GAC sampling event will be conducted in September 2003. In March 2003, post-GAC results reported toluene in LS-7-A2 (0.52 �g/L) and in LS-2/LS-3-A2 (0.86 �g/L). As described previously, toluene is believed to be associated with tape used to secure sample labels to the bottles.

Results for PCE, TCE, and cis-1,2-DCE in pre-GAC samples collected from the Leon Springs Villa community in the March 2003 sampling event are provided below.

Other previous detections in Leon Springs wells include 1,2‑dichloroethane (1,2-DCA) detected in LS-4 in March 2002 at a concentration of 0.12 mg/L. Detections of chloroform have occurred in LS-7 since March 2000; maximum values reported being slightly above the MDL, but well below the MCL of 80 �g/L. Chloroform was detected in March 2003 in wells LS-1 (0.42 �g/L) and LS-3 (0.12 �g/L). Methylene chloride (0.25 mg/L) was reported in LS‑5 in March 2002 and September 2002, but was not detected in March 2003.

Cumulative summaries of VOC sampling results for wells in the Leon Springs Villa area can be found in Volume 5, Table 8, CSSA Environmental Encyclopedia.

3.7 - Old Fredericksburg Road Area

March 2003 Results

Three wells (OFR-1, OFR-2, and OFR-3) were sampled along Old Fredericksburg Road in March 2003. PCE was detected at 0.37 mg/L in well OFR‑1. The results for OFR-2 include PCE at a concentration of 0.11 mg/L and toluene at a concentration of 0.62 mg/L. These wells should be monitored quarterly, in accordance with the Plan. No trend analysis was prepared for these wells because detections have not exceeded the RL or MCL.

In March 2003, OFR-3 had detections of PCE (2.81 mg/L), TCE (3.25 mg/L), and dichlorodifluoromethane (1.04 mg/L). The concentrations were above the MDL and RL but below the MCL. In April 2002, a GAC unit was installed on OFR-3 due to prior PCE concentrations above the MCL. An evaluation of concentration trends in well OFR-3 through March 2003 is provided in Figure 3.5. Increases in PCE and TCE occurred from February to March 2002. PCE and TCE decreased from June 2002 to September 2002 and both slightly increased from September to December 2002. The March 2003 event showed a slight decrease in the PCE and TCE concentrations. OFR-3 should continue to be sampled on a quarterly schedule.

Results Summary

OFR-2 was first sampled in December 1995 to determine whether VOCs had migrated off-post to the west of CSSA. Although PCE, TCE, and cis-1,2-DCE were not detected in 1995, samples collected in this area since 2001 have contained PCE concentrations of up to 12.15 μg/L, and TCE and cis-1,2-DCE have also been detected sporadically in the past. Every six months, post-GAC samples are collected to confirm the filtration system is working. To date, no VOCs have been detected above the MCLs in the post-GAC samples. The next post-GAC confirmation sample for OFR‑3 will be collected in September 2003 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 in the March 2003 sampling event are provided below.

Methylene chloride has been detected periodically in OFR-1 with concentrations ranging from 0.32 to 1.35 mg/L. In September 2002 methylene chloride was reported at 0.96 mg/L in OFR-2. No methylene chloride was detected in March 2003. Other analytes detected over time in OFR-3 include dichlorodifluoromethane and methylene chloride. Concentrations of these analytes have ranged from 0.28 to 1.57 mg/L and non-detect to 0.96 mg/L, respectively. Methylene chloride is suspected to be a laboratory contaminant.

Cumulative summaries of VOC test results from the Old Fredericksburg area can be found in Volume 5, Table 8, CSSA Environmental Encyclopedia.

3.8 - Ralph Fair Road Area

March 2003 Results

In March 2003, three wells (RFR-10, RFR-11, and RFR-12) were sampled in the Ralph Fair Road area. PCE and TCE were detected in RFR-12 at 0.10 �g/L and 0.23 �g/L, respectively. These values are below the RL, but above the MDL.

RFR-10 concentrations exceeded the MCL for PCE and TCE at 13.88 mg/L and 8.37 mg/L, while cis-1,2 DCE was less than the RL and MCL at a concentration of 0.31 mg/L. An evaluation of concentration trends through March 2003 is included in Figure 3.6. Concentrations of PCE in October 2001 were the maximum concentration reported of 20.89 mg/L. PCE concentrations decreased until March 2002. PCE concentrations increased from 4.50 to 14.94 mg/L from March 2002 to December 2002. From December 2002 to March 2003, PCE concentration decreased slightly while the TCE concentration increased. RFR-10 should continue to be sampled on a quarterly schedule.

In March 2003, RFR-11 had detections of PCE (10.02 mg/L) and TCE (0.12 mg/L). PCE concentrations in RFR-11 were again above the MCL, after dropping below the MCL in June 2002. The maximum concentration, 16.73 �g/L, was detected in October 2001 (Figure 3.7). TCE levels decreased from the December 2002 level of 0.67 mg/L to 0.12 mg/L in March 2003. PCE levels also began to decrease from December 2002 to March 2003, however the concentration is still above the MCL (5.0 �g/L). RFR-11 should continue to be sampled on a quarterly schedule.

RFR-10 and RFR-11 required the installation of GAC filtration systems in October 2001 when concentrations exceeded the MCL. Post-GAC sampling confirms that the GAC filtration systems are reducing VOCs to concentrations below the applicable MCLs for drinking water. The post-GAC samples from RFR-11 in March 2003 had detections of PCE (0.07 mg/L) and toluene (0.07 mg/L) and RFR-10 had a detection of toluene (0.12 �g/L). Upon arrival at well RFR-11 it was noted that the GAC filtration system was bypassed for an unknown amount of time. After speaking to the well owner, the field team was informed that the GAC was bypassed due to water pressure problems. Based on further system review, a water leak was discovered at a residential building. After the leak was repaired, water pressures returned to normal. If the GAC system is bypassed again in the future, the possibility of installing a lock will be discussed with the well owner. See Appendix C for previous post-GAC sampling results. Future post-GAC sampling is scheduled on a semi-annual basis and the next post-GAC confirmation samples will be collected in September 2003.

Results Summary

During the first off-post sampling performed in 1995, Ralph Fair Road wells RFR-3 and RFR-8 were sampled. March 2003 results for pre-GAC samples collected for wells in the Ralph Fair Road area are provided below.

Cumulative summaries of VOC sample results for the Ralph Fair Road area can be found in Volume 5, Table 8, CSSA Environmental Encyclopedia.

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