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Final March 2004

Off-Post Quarterly Groundwater Monitoring Report

Section 3 - Analytical Results

Twenty-one wells contained VOCs at concentrations above the MDL in March 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 a discussion of the March 2004 results.  Concentrations of VOCs detected in March 2004 are presented in Table 3.1.  Full analytical results from the March 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 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 and the AOC-65 weather station, for evaluation of the effects of precipitation on concentrations, if any.  These figures are presented prior to the discussion of March 2004 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 quarterly groundwater monitoring program conducted from June 2001 to December 2003 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 March 2004 CSSA off-post data.  The matrix spike analyzed on sample JW-9 in data package TO08-#24 (APPL ID 43889) had 1,1-dichloroethene (1,1-DCE) approximately 3% below the lower acceptance criteria of 75%.  This analyte met criteria in the MSD.  In accordance with the CSSA QAPP, the results for 1,1-DCE were flagged �M� for all samples in this SDG.  All data for the March 2004 off-post groundwater monitoring event is considered usable.

Methylene chloride has been detected 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 2003, September 2003, December 2003, or March 2004 sampling events. 

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 over the combined MCL.  These compounds are regulated as disinfection byproducts related to disinfectants added to drinking water systems.  The levels detected off-post are related to disinfection of the drinking water well by the off-post well owner. 

3.1       Dominion

March 2004 Results:

In March 2004, well DOM-2 was sampled in the Dominion area.  No VOCs were detected in this well.  DOM-2 has been sampled annually since March 2002.  VOCs have not been detected in this well.

3.2       Fair Oaks

March 2004 Results:

In March 2004, wells FO-J1 and FO-8 were sampled in the Fair Oaks area.  PCE was detected in FO-J1, at a concentration of 0.36 �g/L, above the MDL but below the RL.  This was the eleventh consecutive quarterly sample collected from FO-J1.  Over the history of the sampling at this well, the PCE levels have ranged from 0.06 to 0.36 �g/L.  FO-J1 will remain on the quarterly sampling schedule for upcoming events.  Well FO-8 had no VOC detections in March 2004.  Since VOCs of concern have not been detected in FO-8; the well will remain on an annual sampling schedule.

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 2004 sampling events are provided in the following table: 

3.3       Hidden Springs Estates

March 2004 Results:

In March 2004, Hidden Springs Estates well HS-2 was sampled.  HS-2 had detections of PCE and toluene at concentrations of 0.14 mg/L and 1.0 mg/L respectively.  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 this well, PCE levels have ranged from 0.11 to 0.22 �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:

3.4       I-10 Area

March 2004 Results:

Two wells were sampled in the I-10 area in March 2004:  I10-2 and I10-4.  Well I10-2 had no VOC detections in March 2004.  PCE and TCE have not been detected in I10-2 since March 2003.  Well I10-4 reported an all time high PCE concentration of 2.22 mg/L.  TCE was also detected below the RL at a concentration of 0.87 mg/L.  Based on these detections, I10-2 will be sampled annually and I10-4 will be added to 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.  Since that time, 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: 

F = Value detected above the MDL, but below the RL

ND = not detected above the MDL

3.5       Jackson Woods

March 2004 Results:

In March 2004, nine Jackson Woods wells (JW-7, JW-8, JW-9, JW-12, JW-14, JW-26, JW‑28, JW-29, and JW‑30) were sampled.  Six of the nine wells sampled had detections of COCs (JW-7, JW-8, JW-9, JW-14, JW-28, and JW-30) but not exceed the applicable MCLs.  JW-12, JW-26, and JW-29 had no VOC detections; however, due to previous detections, JW-26 and JW-29 will continue to be monitored on a quarterly basis in accordance with the Plan.  JW-12 will be sampled as needed.

Well JW-7 was initially sampled in September 2003 and December 2003, and for the third consecutive event had a detection of PCE at a concentration of 0.42 �g/L, which is above the MDL but below the RL.  Over the sampling history of this well PCE has ranged from 0.42 to 0.65 �g/L.

PCE was detected below the RL (0.35 �g/L) for the fourth consecutive sampling event in JW-8.  Well JW-9 had PCE detected at a concentration of 0.15 �g/L, below the RL.  Over the sampling history of these wells, PCE levels have ranged between 0.29 to 0.35 �g/L for JW-8 and 0.06 to 0.15 �g/L for JW-9. 

Chloroform (1.3 �g/L) and bromodichloromethane (0.13 �g/L), were detected in JW-14.  Chloroform has been consistently detected in this well and has reported a range between 0.06 to 0.16 �g/L, since sampling began in September 2001. All chloroform results have been below the chloroform/combined trihalomethanes MCL of 80 mg/L. 

JW-26 had no VOC detections this event but will remain on the quarterly sampling schedule in accordance with the Plan.  Since sampling began at this well, PCE levels have ranged from 0.06 to 0.14 �g/L.  Additional samples were collected from faucets located inside the residence at the well owners� request.  No VOCs were detected in those samples.

JW-28 was sampled for the third consecutive event and toluene was detected at a concentration of 0.20 mg/L (below the RL).  The toluene range over the sampling history for this well is 0.13 to 0.22 �g/L.   JW-30 had a detection of PCE (0.15 �g/L, below the RL) for the fourth consecutive sampling event.  The PCE range for this well is 0.06 to 0.2 �g/L.

Wells JW-12, JW-26, and JW-29 had no VOC detections in March 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, 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.  Since then, several Jackson Woods wells have been added to the sampling list.  Results for PCE, TCE, and cis-1,2-DCE from wells in the Jackson Woods area sampled during the 2004 sampling events are provided below:

F = Value detected above the MDL, but below the RL   ND = not detected above the MDL

FD = Field Duplicate sample

3.6       Leon Springs Villa

March 2004 Results:

Seven wells (LS-1, LS-2, LS-3, LS-4, LS-5, LS-6, and LS-7) in the Leon Springs Villa subdivision were sampled during the March 2004 sampling event.  All of the seven wells had detections of COCs; however, none of the detections were above the applicable MCLs.

PCE, TCE, and chloroform were detected in LS-1 at concentrations of 0.28 mg/L, 0.2 mg/L, and 0.13 mg/L respectively.  All concentrations were 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.  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.

LS-2 had detections of PCE and TCE, at concentrations of 0.98 mg/L and 0.11 mg/L, respectively, in March 2004.  Both concentrations were above the MDL and below the RL.  An evaluation of concentration trends through the March 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 have been decreasing and they have now fallen below 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 1.09 mg/L and TCE at 0.17 mg/L, both below the RL.  An evaluation of concentration trends through March 2004 in well LS-3 is given in Figure 3.1.  Based on previous detections, wells LS-2 and LS-3 had a combined GAC filtration system installed by CSSA in April 2002.  LS‑2 and LS-3 should be sampled quarterly in the future.

In March 2004, chloroform was detected at a concentration of 0.16 mg/L in LS-4, below the RL.  LS-4 should continue to be sampled quarterly due to previous VOC detections above the MDL, which has ranged from 0.06 to 0.25 mg/L.

LS-5 had a TCE detection of 0.16 mg/L in this event.  The concentration was above the MDL and below the RL and MCL.  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 March 2004, PCE and TCE were detected at concentrations of 3.61 mg/L and 0.47 mg/L, respectively, in LS-6.  TCE was below the RL and PCE was above the RL but below the MCL.  An evaluation of concentration trends in LS‑6 through March 2004 is provided in Figure 3.1.  Well LS-6 is equipped with a GAC treatment system due to past VOC concentrations.  Well LS-6 should continue to be sampled on a quarterly schedule. 

The LS-7 sample had concentrations of PCE (3.1 mg/L), TCE (0.33 mg/L), and chloroform (0.12 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 was below the MCL and above the RL.  Well LS-7 was equipped with a GAC treatment system due to previous detections.  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, and again in March 2004.  This quarter TCE was 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 no VOC detections.   The next post-GAC sampling event will be conducted in September 2004. 

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:

F = Value detected above the MDL, but below the RL   ND = not detected above the MDL 

3.7       Old Fredericksburg Road Area

March 2004 Results:

Four wells (OFR-1, OFR-2, OFR-3, and OFR-4) along Old Fredericksburg Road were sampled in March 2004.  Three wells had detections of VOCs.

PCE was detected at 0.39 mg/L in well OFR‑1, below the RL.  The results for OFR-2 indicated PCE at a concentration of 0.35 mg/L, also below the RL.  The field duplicate sample for OFR-2 had PCE at 0.31 �g/L, 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 not exceeded the MCL.

In March 2004, OFR-3 had detections of PCE (2.87 mg/L), TCE (1.98 mg/L), and  dichlorodifluoromethane (0.29 mg/L).  The PCE and TCE concentrations were above the MDL and RL.  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 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.  March 2004 concentrations decreased to below the applicable MCLs.  OFR-3 should continue to be sampled on a quarterly schedule. 

Well OFR-4 had no VOC detections in March 2004 and no previous detections.  OFR-4 can remain on the quarterly monitoring schedule or be sampled as needed. 

Results Summary:

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 the RLs in the post-GAC samples.  The next post-GAC confirmation sample for OFR‑3 will be collected in September 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 sampled during the 2004 events are provided below:

3.8       Ralph Fair Road Area

March 2004 Results:

In March 2004, six wells (RFR-3, RFR-4, RFR-5, RFR-10, RFR-11, and RFR-12) in the Ralph Fair Road area were sampled.  Of the six wells sampled, only one well, RFR-10, had detections greater than the MCL.

Wells RFR-3, RFR-4, RFR-5, and RFR-12 had no VOC detections.  RFR-4 and RFR-5 were sampled for the first time this quarter.  RFR-3 and RFR-12 will remain on the quarterly sampling schedule, due to previous detections, in accordance with the Plan.  VOCs have ranged from 0.05 to 0.12 �g/L in RFR-3 and from 0.05 to 0.24 �g/L in RFR-12.

RFR-10 concentrations exceeded the MCLs for PCE and TCE at 23.23 mg/L and 10.25 mg/L, respectively, while cis-1,2-DCE was less than the RL and MCL at a concentration of 0.44 mg/L.  An evaluation of concentration trends through March 2004 is included in Figure 3.1.  Due to previous detections, a GAC filtration system was installed on RFR-10.  RFR-10 should continue to be sampled on a quarterly schedule. 

In March 2004, RFR-11 had detections of PCE (0.99 mg/L, below the RL) and TCE (1.25 mg/L), both of which were below the 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.

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

F = Value detected above the MDL, but below the RL

ND = not detected above the MDL

Bolded Data = Results > MCL

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