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September 2003 Off-Post Quarterly Groundwater Monitoring Report

Section 3 - Groundwater Monitoring Analytical Results

Twenty-three wells contained VOCs at concentrations above the MDL in September 2003. 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 I10-4 to the west and LS-4 to the south. Information which includes depth of wells, pump depth, and other pertinent data necessary to properly characterize the vertical extent of migration is not readily available from most well owners.

Off-post wells are grouped by community or neighborhood for a discussion of the September 2003 results. Concentrations of VOCs detected in September 2003 are presented in Table 3.1. Full analytical results from the September 2003 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 have had detections of PCE and TCE that approach and/or exceed the MCLs. Figure 3.1 also includes 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 prior to discussion of September 2003 groundwater sampling results for each neighborhood. 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 June 2001 through June 2003 is available in the Annual Groundwater Monitoring Report, (Parsons, 2003, currently draft) and/or previous groundwater reports, located in Volume 5, Groundwater of the CSSA Environmental Encyclopedia.

Methylene chloride has been reported on- and off-post since 1992. However, for historical methylene chloride detections, methylene chloride was also present in associated quality control samples at concentrations below the RL, 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. Three detections of methylene chloride reported in March 2003 were flagged with a �B� flag, as the concentrations of methylene chloride were above the RL in the method blank. Methylene chloride was not detected in the June or September 2003 sampling events.

3.1 - Fair Oaks

September 2003 Results:

In September 2003, well FO-J1 was sampled in the Fair Oaks area. PCE was the only VOC detected in FO-J1, at a concentration of 0.30F, above the MDL but below the RL. This was the ninth consecutive quarterly sample collected from FO-J1. FO-J1 will remain on the quarterly sampling schedule for upcoming events. After a minimum of one year with no detections, the sampling frequency will be reviewed and possibly decreased in accordance with the 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 during the March, June, and September 2003 sampling events are provided below:

3.2 - Hidden Springs Estates

September 2003 Results:

In September 2003, HS-2 was sampled in Hidden Springs Estates. HS-2 had a detection of PCE at a concentration of 0.12 mg/L. This concentration was above the MDL, but below the RL. Based on this detection, HS-2 will remain on the quarterly sampling schedule in accordance with the Plan.

Results Summary:

Wells in Hidden Springs Estates were first included in CSSA�s groundwater monitoring program in December 2001. Results for PCE, TCE, and cis-1,2-DCE from the Hidden Springs area wells sampled in the March, June, and September 2003 sampling events are provided below:

3.3 - I-10 Area

September 2003 Results:

Two wells were sampled in the I-10 area in September 2003: I10-2 and I10-4. Well I10-2 had no VOC detections; however, based on historical results, I10-2 will continue to be monitored on a quarterly basis in accordance with the Plan. No VOCs were detected in I10-4 in September 2003. This is the seventh consecutive sampling event with no PCE, TCE, or 1,2-DCE detected in well I10-4. However, since methylene chloride has been detected (as a result of laboratory processes), I10-4 will not be removed from the quarterly sampling schedule until it is established conclusively that methylene chloride is not a COC.

Results Summary:

Wells in the I-10 area were first included in CSSA�s groundwater monitoring program in September 2001. Results for PCE, TCE, and cis-1,2-DCE from I-10 area wells sampled during the March, June, and September 2003 sampling events are provided in the following table:

3.4 - Jackson Woods

September 2003 Results:

In September 2003, eight Jackson Woods wells (JW-7, JW-8, JW-9, JW-14, JW-26, JW-28, JW-29, and JW‑30) were sampled. Three of the eight wells sampled had detections of COCs (JW-7, JW-8, and JW-30) that do not exceed the applicable MCLs or RLs. JW-9 and JW-29 had no VOC detections; however, due to previous results, will continue to be monitored on a quarterly basis in accordance with the Plan.

JW-7 was sampled for the first time and had a detection of PCE at a concentration of 0.54 �g/L, which is above the MDL but below the RL. PCE was detected below the RL (0.29 �g/L) for the second sampling event for JW-8. Chloroform (0.22 �g/L) was the only VOC detected in JW-14 below the RL. Chloroform has been consistently reported in this well since sampling began in September 2001 and all results have been below the MCL of 80 mg/L. JW-26 also had a detection of chloroform (0.18 �g/L, below the RL). This is the second detection of chloroform since March 2002. JW-28 was sampled for the first time this quarter and toluene was detected at a concentration of 0.13 mg/L, below the RL. JW-30 had a detection of PCE (0.20 �g/L, below the RL) for the second consecutive sampling event. JW-30 was sampled for the first time in December 1995, then again in September 1999. During the 1995 and 1999 sampling events, methylene chloride was the only VOC detection. JW-7, JW-8, JW-9, JW-14, JW-26, 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, and no VOCs were detected in the JW‑30 well 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 additional wells have been added since that time. Results for PCE, TCE, and cis-1,2-DCE from wells in the Jackson Woods community sampled during the March, June, and September 2003 sampling events are provided below:

3.5 - Leon Springs Villa

September 2003 Results:

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 during the September 2003 sampling event. All of the seven wells had detections of COCs; however, none of the detections were above the applicable MCLs.

PCE was the only VOC detected in LS-1 at 0.24 mg/L, below the RL. Previously, LS-1 has also had detections of chloroform in eight consecutive events. All detections of chloroform have been below the combined trihalomethanes MCL (80 mg/L) for chloroform. LS-1 should remain on the quarterly sampling schedule.

LS-2 had detections of PCE and TCE, at concentrations of 2.21 mg/L and 0.39 mg/L, respectively, in September 2003. PCE and TCE were detected at concentrations of 1.7 �g/L and 0.41 �g/L in the field duplicate of LS-2. Chloroform was also detected at a concentration of 0.10 mg /L in the field duplicate for LS-2. PCE concentrations were above the RL and below the MCL. The TCE and chloroform were above the MDL and below the RL and MCL. An evaluation of concentration trends through September 2003 for LS-2 is given in Figure 3.1.

PCE concentrations doubled from September to December 2002. From December 2002 to June 2003 PCE levels decreased to below the MCL and have remained steady since. 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 1.37 mg/L and TCE at 0.14 mg/L, below the RL. An evaluation of concentration trends through September 2003 in well LS-3 is given in Figure 3.1. 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 from 1.06 mg/L to 4.42 mg/L between June 2002 and December 2002. 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. Based on the September 2003 and previous sampling events, LS‑2 and LS-3 should be sampled quarterly in the future.

In September 2003, PCE and chloroform were detected at concentrations of 0.12 mg/L and 0.26 mg/L in LS-4, respectively both below the RL. LS-4 should continue to be sampled quarterly due to VOCs detected above the MDL.

LS-5 had a TCE detection of 0.20 mg/L 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 September 2003, PCE and TCE were detected at concentrations of 2.49 mg/L and 0.38 mg/L, respectively, in LS-6. TCE was below the RL. An evaluation of concentration trends in LS‑6 through September 2003 is provided in Figure 3.1. After the maximum detection of 10.0 mg/L in September 2001, PCE concentrations did not exceed the MCL again until December 2002 at 6.86 mg/L, while TCE remained below the RL and 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 (3.47 mg/L), TCE (0.34 mg/L), and chloroform (0.28 mg/L) during this event. Both TCE and chloroform were below the RL. As shown by the concentration trends presented in Figure 3.1, PCE concentrations reported in March 2003 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). Testing has confirmed 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. The next post-GAC sampling event will be conducted in March 2004.

Results for PCE, TCE, and cis-1,2-DCE in pre-GAC samples collected from the Leon Springs Villa community during March, June, and September 2003 are provided below:

3.6 - Old Fredericksburg Road Area

September 2003 Results:

Four wells (OFR-1, OFR-2, OFR-3, and OFR-4) were sampled along Old Fredericksburg Road in September 2003. Of the four wells tested, three had detections of COCs, and one well, OFR-3, exceeded applicable MCLs.

PCE was detected at 0.49 mg/L in well OFR‑1, below the RL. The results for OFR-2 include PCE at a concentration of 0.26 mg/L, also below the RL. These wells should continue to be monitored quarterly, in accordance with the Plan. No trend analysis was prepared for these wells because detections have not exceeded the MCL. Well OFR‑4 was sampled for the second time this sampling event. No VOCs were detected in OFR-4, and it will be sampled in the future on an as needed basis.

In September 2003, OFR-3 had detections of PCE (10.82 mg/L), TCE (6.42 mg/L), and dichlorodifluoromethane (1.09 mg/L). The PCE and TCE concentrations were above the MDL, RL, and 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 September 2003 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 September 2003 event showed a significant increase in the PCE and TCE concentrations, both parameters exceeding their MCLs for the second time. 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 from OFR-3 since 2001 have contained PCE and TCE concentrations above the MCL, 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 at OFR-3 is working. To date, no VOCs have been detected above the RLs in the post-GAC samples. The next post-GAC confirmation sample for OFR‑3 will be collected in March 2004 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 during the March, June, and September 2003 events are provided below:

3.7 - Ralph Fair Road Area

September 2003 Results:

In September 2003, four wells (RFR-9, RFR-10, RFR-11, and RFR-12) were sampled in the Ralph Fair Road area. Of the four wells sampled, only one well, RFR-10, had detections greater than the MCL.

Well RFR-9 had no detections of PCE, TCE, or cis-1,2-DCE during this sampling event. There have been previous detections of methylene chloride, which is likely due to laboratory processes. RFR-9 will continue to be sampled until methylene chloride is conclusively established to be present due to laboratory processes. TCE was detected in RFR-12 at 0.14 �g/L. This value is below the RL, but above the MDL. RFR-9 and RFR-12 will continue to be sampled on a quarterly schedule.

RFR-10 concentrations exceeded the MCLs for PCE and TCE at 23.56 mg/L and 10.07 mg/L, while cis-1,2-DCE was less than the RL and MCL at a concentration of 0.40 mg/L. Chloroform was also detected at a concentration of 0.21 mg/L, below the RL. An evaluation of concentration trends through September 2003 is included in Figure 3.1. Concentrations of PCE in June 2003 were the maximum concentration reported, until this event, of 23.56 mg/L. PCE concentrations decreased until March 2002 but 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. In September 2003 RFR-10 exceeded its previous maximum concentration for both PCE and TCE (23.56 mg/L and 10.07 mg/L, respectively). RFR-10 should continue to be sampled on a quarterly schedule.

In September 2003, RFR-11 had detections of PCE (0.99 mg/L below the RL) and TCE (1.63 mg/L), both of which were below the MCL. The PCE concentration was below the MCL in only two other events, June 2002 and June 2003. TCE levels decreased from the December 2002 level of 0.67 mg/L to 0.12 mg/L in March 2003, while in recent sampling event TCE concentrations have increased. PCE levels also began to decrease from December 2002 to September 2003. Based on previous results, RFR-11 should continue to be sampled on a quarterly schedule.

Results Summary:

Ralph Fair Road wells RFR-3 and RFR-8 were sampled during the first off-post sampling performed in 1995. 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 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 March 2004. March, June, and September 2003 results for pre-GAC samples collected for wells in the Ralph Fair Road area are provided below:

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