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September 2004 Off-Post Quarterly Groundwater Monitoring Report

Section 3 - September 2004 Groundwater Monitoring Analytical Results

Twenty wells contained VOCs at concentrations above the MDL in September 2004.  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.

Off-post wells are grouped by community or neighborhood for the following discussion of the September 2004 results.  Concentrations of VOCs detected in September 2004 are presented in Table 3.1.  Full analytical results from the September 2004 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 September 2004 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 June 2004 is available in previous quarterly reports, located in Volume 5, Groundwater of the CSSA Environmental Encyclopedia.

No problems were identified during data verification performed on the September 2004 CSSA off-post data.  All data for the September 2004 off-post groundwater monitoring event is considered usable.

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, one detection was particularly high prompting further investigation.  An additional sample was collected to verify the anomalous results.

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 bleach to the drinking water well for disinfection.

3.1 - Fair Oaks

September 2004 Results:

In September 2004, well FO-J1 in the Fair Oaks area was sampled.  PCE was detected at a concentration of 0.17 �g/L, below the RL.  A sample was not collected from well FO-J1 in June 2004 due to an electrical malfunction.  PCE was detected in FO-J1 at a concentration of 0.36 �g/L, above the MDL but below the RL, in March 2004.

Results Summary:

Wells in the Fair Oaks area were first sampled in September 2001.  Twelve quarterly samples were collected from FO-J1 through September 2004.  PCE levels have ranged from 0.06 to 0.36 �g/L.  FO-J1 will remain on the quarterly sampling schedule for upcoming events.  Results for PCE, TCE, and cis-1,2-DCE from wells sampled in the Fair Oaks area during the 2004 sampling events are provided in the following table: 

3.2 - Hidden Springs Estates

September 2004 Results:

In September 2004, Hidden Springs Estates well HS-2 was sampled.  Well HS-2 had a detection of PCE at a concentration of 0.23 �g/L this quarter.  HS-2 has no VOC detections in June 2004.  However, this well did have detections of PCE and toluene at concentrations of 0.14 mg/L and 1.0 mg/L, respectively, in March 2004.  These concentrations were above the MDL, but below the RL.  Based on these detections, 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.  Over the history of the sampling at well HS-2, PCE levels have ranged from 0.11 to 0.23 �g/L.  Results for PCE, TCE, and cis-1,2-DCE from the Hidden Springs area wells sampled in the 2004 sampling events are provided below:

3.3 - Interstate I-10 Area

September 2004 Results:

Two wells in the I-10 area were sampled in September 2004:  I10-2 and I10-4.  Well I10‑2 had a VOC detection of PCE (0.11 mg/L), below the RL.  The field duplicate reported similar results with the addition of methlyene chloride, a suspected laboratory contaminant.  Well I10-4 also reported a PCE detection of 0.15 �g/L in September 2004.  In March 2004 well I10-4 reported its maximum detected PCE concentration of 2.22 mg/L.   Based on these detections, I10-2 and I10-4 will remain on the quarterly sampling schedule in accordance with the Plan.

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 2004 sampling events are provided in the following table: 

3.4 - Jackson Woods

September 2004 Results:

In September 2004, eight Jackson Woods wells (JW-7, JW-8, JW-9, JW-14, JW-26, JW-28, JW-29, and JW‑30) were sampled.  Four of the eight wells sampled, JW-7, JW-8, JW-14, and JW-28, had detections of contaminants of concern below the applicable RLs and MCLs.  Wells JW-9, JW-26, JW-29, and JW-30 had no VOC detections.  Wells JW-7, JW-8, JW-9, JW-14, JW-26, 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 five quarters but will remain on the quarterly sampling schedule due to its proximity to impacted wells.

Well JW-7 was initially sampled in September 2003.  The September 2004 sampling event was the fifth consecutive round of sampling at JW-7.  The initial sample results reported methylene chloride at 19.24 �g/L and dichlorodifluoromethane at 0.13 �g/L.  Due to the unusually high concentration of methylene chloride an additional sample was collected on October 18, 2004.  These results came back as all non-detect leading Parsons to reject the sample results as anomalous data due to laboratory contamination.  PCE concentrations in this well have ranged from 0.42 to 0.65 �g/L.

PCE was detected in well JW-8 at a concentration of 0.27 �g/L, below the RL, in September 2004.  PCE was detected below the RL in well JW-8 for five consecutive sampling events prior to the September 2004 event.  PCE levels have ranged between 0.29 to 0.35 �g/L.

No VOCs were detected in wells JW-9, JW-26, JW-29, and JW-30 this event.  PCE levels have ranged between 0.06 to 0.15 �g/L for well JW-9.

PCE (0.12 �g/L) and chloroform (0.11 �g/L) were detected in JW-14.  PCE was last detected in this well in March 2003; all PCE detections have been below the RL.  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 chloroform is most likely the result of the well owners routine disinfection of the well with bleach.

Well JW-26 had no VOC detections this event but will remain on the quarterly sampling schedule in accordance with the Plan.  Historic PCE levels have ranged from 0.06 to 0.14 �g/L.

Well JW-28 was sampled for the fifth consecutive event and toluene was detected at a concentration of 0.24 mg/L (below the RL).  Toluene concentrations have ranged between 0.12 and 0.24 �g/L since June 2003.  The field duplicated reported similar results.

Wells JW-29 and JW-30 had no VOC detections this sampling event.  Well JW-29 had a PCE detection in June 2003.  Although well JW-29 has had five consecutive sampling events with no VOC detections it will remain on the quarterly sampling schedule because it is near impacted wells.  Well JW-30 had four consecutive detections of PCE prior to the June 2004 event.  PCE concentrations have ranged from 0.06 to 0.2 �g/L in JW-30.

Wells JW-9, JW-26, JW-29, and JW-30 had no VOC detections in September 2004.  Wells 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 with sampling at JW-30, and 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 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 2004 sampling events are provided below:

3.5 - Leon Springs Villa

September 2004 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 September 2004.  LS-2, LS-3, LS-4, LS-6 and LS-7 had detections below the applicable MCLs.

Well LS-1 has been taken offline by Bexar Met. due to homeowners complaints of cloudy water.  LS-1 had no VOC detections in June 2004.  Well LS-1 had detections of chloroform in eight previous events.  All detections of chloroform have been below the TTMs MCL (80 mg/L).  PCE and TCE have been detected consistently in this well ranging from 0.24 to 0.67 �g/L for PCE and 0.05 to 0.51 �g/L for TCE.  Well LS-1 should remain on the quarterly sampling schedule.

Well LS-2 had detections of PCE and TCE at concentrations of 1.41 mg/L and 0.26 mg/L, respectively, in September 2004.  The field duplicate reported similar results.  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 September 2004 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 up 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 1.81 mg/L, TCE at 0.24 mg/L, toluene at 4.59 mg/L, and chloroform at 0.26 mg/L, all below the RL.  An evaluation of concentration trends through September 2004 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.  Wells LS‑2 and LS-3 should continue to be sampled quarterly in the future.

In September 2004, PCE was detected at a concentration of 0.12 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 0.16 mg/L in September 2004.  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.  Well LS-5 should remain on the quarterly sampling schedule.

In September 2004, PCE, dibromochloromethane, and bromodichloromethane were detected at concentrations of 2.08 mg/L, 0.14 mg/L and 0.16 mg/L, respectively, in LS-6.  PCE was above the RL but below the MCL while all other detected concentrations fell below the RL.  An evaluation of concentration trends in LS‑6 through September 2004 is provided in Figure 3.1.  Well LS-6 is equipped with a GAC treatment system because concentrations exceeded the MCL in the past.  Well LS-6 should continue to be sampled on a quarterly schedule.

The LS-7 sample contained concentrations of PCE (2.77 mg/L), TCE (0.26 mg/L), and chloroform (0.11 mg/L) during this sampling event.  TCE and chloroform were 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.  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.  Semi-annual post-GAC confirmation samples have been 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, and again in September 2004.  In March 2004 TCE was detected below the RL, in sample LS-2/LS-3-A1.  In September 2004 PCE (0.59 mg/L) and TCE (0.22 mg/L) were detected 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 0.12 mg/L, below the RL.  Due to current detections a maintenance visit has been scheduled to change the carbon in the LS-2/LS-3 GAC unit.  The next post-GAC sampling event will be conducted in March 2005.

Results for PCE, TCE, and cis-1,2-DCE in pre-GAC samples collected from the Leon Springs Villa community wells during 2004 are provided below:

3.6 - Old Fredericksburg Road Area

September 2004 Results:

Three wells (OFR-1, OFR-2, and OFR-3) along Old Fredericksburg Road were sampled in September 2004.  All three wells had detections of VOCs.

PCE was detected at 0.35 mg/L, in well OFR‑1, which is below the RL.  The field duplicate reported a PCE concentration of 0.38 mg/L.  The results for OFR-2 indicated PCE at a concentration of 0.32 mg/L, also below the RL.  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 September 2004, OFR-3 had detections of PCE (1.61 mg/L), TCE (1.67 mg/L), and dichlorodifluoromethane (0.46 mg/L).  The PCE and TCE concentrations were above the MDL and 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 September 2004 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 March 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 2004 events are provided below:

3.7 - Ralph Fair Road Area

September 2004 Results:

In September 2004, five wells (RFR-3, RFR-9, RFR-10, RFR-11, and RFR-12) in the Ralph Fair Road area were sampled.  Of the five wells sampled, only one well, RFR-10, had detections greater than the MCL.

Wells RFR-3 and RFR-9 had no VOC detections.  Well RFR-3 will remain on the quarterly sampling schedule in accordance with the Plan.  VOCs have ranged from 0.005 to 0.12 �g/L in RFR-3.  Well RFR-9 can continue to be sampled annually.

Well RFR-10 concentrations exceeded the MCLs for PCE at 18.76 mg/L and TCE exceeded the MCL at a concentration of 7.99 mg/L, while cis-1,2-DCE was less than the RL and MCL at a concentration of 0.43 mg/L.  An evaluation of concentration trends through September 2004 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 September 2004, RFR-11 had detections of PCE (1.93 mg/L) and TCE (1.05 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.

Well RFR-12 had a detection of TCE at a concentration of 0.11 �g/L, which is below the RL.  Well RFR-12 will remain on the quarterly sampling schedule in accordance with the Plan.

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 previous post-GAC sampling results.  The next post-GAC confirmation samples will be collected in March 2005.  Results in 2004 for wells in the Ralph Fair Road area are provided below:

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