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December 2001 Off-Post Quarterly Groundwater Report
Section 3 - Previous Off-Post Groundwater Sampling Results
Quarterly off-post groundwater monitoring was performed from December 17 through December 20, 2001. Additional samples were collected in late September, October and November 2001. Off-post wells sampled during this quarterly monitoring event were selected based on previous test results and proximity to wells with detectable levels of PCE and TCE and the post boundary. Public and private supply wells located west and south of CSSA were selected for the second round of quarterly off-post sampling. Figure 1.1 illustrates the locations of off-post private and public wells sampled during the December 2001 quarterly event.
Wells with detected concentrations above 80% of the appropriate MCL are sampled on a monthly schedule. Prior to the December 2001 quarterly sampling event, samples were collected from selected wells of concern based on results from the September 2001 monitoring. Seven wells were sampled various times from late September through November (LS-2, LS-3, LS-5, LS-6, LS-7, OFR-3, RFR-10, and RFR-11). The results from these monthly sampling events are presented in Section 4, along with the December 2001 quarterly sampling event results.
One public supply well was sampled in the Fair Oaks area (FO-J1). This well is located approximately 8,000 feet southwest of the SWMU B-3 and O-1 source areas, and 3,200 feet north-northwest of the Building 90/AOC-65 site. Two privately owned wells were sampled in the Jackson Woods subdivision (JW-9 and JW-14), located west of CSSA and south of Fair Oaks. Two wells were sampled in the I-10 area (I10-2 and I10-4), which is southwest of CSSA and west of the suspected source area AOC-65. Seven wells in the Leon Springs area were sampled, four public wells, LS-1, LS-2, LS-3, and LS-4, and three privately owned wells, LS-5, LS-6, and LS-7. Leon Springs is located south of CSSA and the suspected contaminant source at AOC-65. Four wells were sampled in the Ralph Fair Road area (RFR-9, RFR-10, RFR-11, and RFR-12), located west of CSSA. Two wells were sampled in the Hidden Springs subdivision, public well HS-2 and HS-3, an unused well. Hidden Springs is located south-east of CSSA and suspected source area at AOC-65. Privately owned wells OFR-1 and OFR-3 were sampled on Old Fredericksburg Road. Old Fredericksburg Road is located southwest of CSSA and west of the suspected source area at AOC-65. In total, twenty off-post wells were sampled during the December 2001 monitoring event (Figure 1.1).
All wells were sampled from a tap as close to the wellhead as possible. Most of the taps were installed by CSSA to obtain a representative sample before pressurization or storage and before it enters the water supply distribution system. Taps were installed on the necessary wells in September 2001. Because LS-6, LS-7, RFR-10, and RFR-11 have GAC units installed, samples were collected before (PRE) and after (POST) treatment. Prior to sample collection, water was flushed to engage the well pump. While the well was pumping, the pH, conductivity, and temperature readings were recorded to confirm adequate purging. When these parameters stabilized, in accordance with the FSP located in the Environmental Encyclopedia, Volume 1-4, the groundwater samples were collected. Field notes including well purging data are included in Appendix C.
The TNRCC collected split samples from HS-2, HS-3, and I10-4 on December 19, 2001. They also collected a sample from I10-5 that Parsons was unable to sample due to access agreement issues with the well owner. The TNRCC provided a copy of all analytical data to CSSA for review, provided in Appendix D.
Each groundwater sample collected was analyzed for VOCs using SW846 Method 8260B by APPL Laboratory in Fresno, California. Twenty groundwater samples, four Post-GAC water samples, one field duplicate sample, one MS/MSD pair, and three trip blanks were submitted to APPL. The Parsons internal data packages DO5084 #16, #17, #19, #20, and #21 contain the analytical results for this sampling event. Laboratory results were reviewed and verified according to the guidelines outlined in the AFCEE QAPP, version 3.0. Data package DO5084 #16 was received by Parsons on January 18, 2002, all others were received on January 21, 2002, and all packages were submitted to AFCEE on February 7, 2002, where they were placed in line for priority review. These data packages were approved by AFCEE in February and March 2002. Separate monthly sampling events occurring in September, October, and November 2001 were contained in Parsons� internal data packages RL83 #54 � 56 and #58-60. These data packages were approved by AFCEE.