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September 2001 Off-Post Quarterly Groundwater Monitoring Report
Section 1 - Previous Off-Post Groundwater Sampling Procedures
February 2002
Off-post groundwater monitoring scoped under the AETC Contract F41689-96-D-0710, Delivery Order 5084, was performed the week of September 17, 2001 at CSSA. Groundwater monitoring conducted under this delivery order began with the September 2001 sampling event and will continue contractually through the June 2002 sampling event. AFCEE/ERD and AFCEE/ERC will provide technical oversight of the groundwater monitoring program with the consent of CSSA.
The primary objective of the off-post groundwater monitoring is to determine whether concentrations of chlorinated VOCs detected in off-post wells exceed safe drinking water standards. A secondary objective of the off-post groundwater monitoring is to determine the lateral and vertical extent of the contaminant plume associated with past releases near Building 90 (AOC 65) or from SWMU B-3. A subsidiary objective of the off-post groundwater monitoring is to assess whether there are apparent trends (decreasing or increasing) in contaminant levels over time in the sampled wells. CSSA was required by the 3008(h) Administrative Consent Order issued by the EPA on May 5, 1991 to identify and locate both privately and publicly-owned groundwater wells within ��mile of CSSA. The Offsite Well Survey Report (Parsons) was submitted in August 2001 to fulfill this requirement. Additional background information on locating and identifying off-post private and public water supply wells is located in the Environmental Encyclopedia, Volume 5, Groundwater. All off-post wells sampled in the past are shown on Figure 1.1, including off-post wells sampled in the September 2001 event.
Results from two wells (LS-6 and LS-7) identified VOCs at concentrations greater than 90 percent of their respective MCLs, prompting CSSA to install and begin maintenance in August 2001 on granular activated carbon (GAC) wellhead treatment systems designed to reduce contaminant levels in the private well owners� water supplies to safe levels. The applicable MCLs for VOCs detected are the maximum contaminant levels (MCL) established by the EPA under the Safe Drinking Water Act. The �greater than 90 percent of MCL� action level complies with the �Off-post Groundwater Monitoring Response Plan� (the Plan) developed by CSSA and finalized in July 2001. Although not a direct objective of the off-post groundwater monitoring program, pre- and post-GAC samples were collected from LS-6 and LS-7 during the September 2001 sampling event to assess whether the GAC treatment units were effectively removing the contaminants from the water supply of each well. Results indicated that the GAC systems are working properly. Results from October 2001 sampling of RFR-10 indicated that a GAC treatment system was necessary for the well and details will be reported in the next quarter. Due to the two post-GAC samples collected, the total number of private wells sampled during the September 2001 sampling event was 18, instead of the 20 wells scoped under the current funding mechanism (AETC Contract F41689-96-D-0710, Delivery Order 5084). Three additional off-post wells (LS-2, LS-3 and RFR-10) were sampled in late September and early October 2001. Results from sampling of RFR-10 indicated that a GAC treatment system was necessary for the well and details will be reported in the next quarter.
An evaluation of whether the DQOs for CSSA�s groundwater monitoring program was attained are presented in Appendix A. The objectives listed in the table also reference appropriate sections of the 3008(h) Order. Overall DQOs for the investigations at CSSA are provided in Volume 1-1 behind the RFI Addendum Tab (Section 11). A comprehensive summary of the results from the September 2001 off-post groundwater sampling event is presented in Appendix B, and abbreviated tables showing only the detected compounds are included in the groundwater results discussion in Section 4 of this report. The cumulative historical results for each off-post well sampled by CSSA are presented in summary tables in Appendix C. The laboratory data packages and associated data validation reports were submitted to AFCEE and CSSA separately.
1.0 - Previous Off-post Groundwater Sampling Procedures
On-post groundwater monitoring was initiated in 1991 in response to VOC contamination detected in CSSA drinking water supply Well CS-16. Sampling of on-post wells was continued periodically until the CSSA quarterly groundwater monitoring program for on-post wells was initiated in December 1999. Results from on-post groundwater sampling are presented in the September 2001 On-post Quarterly Groundwater Monitoring Report (Parsons, January 2002).
Off-post sampling was first performed in 1995 in response to VOC contamination detected in on-post Well CS-16. Four off-post wells (RFR-3, RFR-8, JW-30, and OFR-2) were sampled. Analytical results for the December 1995 sampling event can be found in the Environmental Encyclopedia, Volume 5, Groundwater Investigation and Associated Source Characterization Report (June 1996), Section 8, specifically Tables 8.2-5 and 8.2-6 or in the Cumulative Off-post Analytical Tables located in Appendix C of this report. These well locations are shown on Figure 1.1, Cumulative Off-post Well Sampling Locations.
In September 1999, wells JW-30, RFR-3, and RFR-8 were resampled to comply with the Interim/Stabilization Measures requirements in the RCRA 3008(h) Administrative Order on Consent. Analytical results for the September 1999 sampling event can be found in the Environmental Encyclopedia, Volume 5-1, December 1999 Quarterly Groundwater Monitoring Report, specifically Table 9 or in the Cumulative Off-Post Analytical Data Tables in Appendix C, attached.
An additional well located at the southwest corner of CSSA, LS-7, was sampled in December 1999 to determine whether VOCs may have migrated to the southwest. Quarterly sampling continued after December 1999 because PCE was detected. Quarterly sampling of LS-7 was included with on-post sampling events until sampling of other off-post wells was initiated in September 2001.
With support from the U.S. Army, CSSA developed response actions that would provide decision-making guidance for responding to detected groundwater contamination. The Off-Post Monitoring Response Plan (the Plan) specifies if VOC contaminant levels are within 90 percent of the MCL (4.5 �g/L for PCE and TCE) and the well is used as a private potable water source, bottled water will be supplied within 24 hours. A confirmation sample will be collected from the well within 14 days of receipt of the final validated analytical report. If the confirmation sample results confirm COC concentrations above the appropriate action levels, the water supply well will be evaluated for installation of a GAC wellhead treatment system or connection to an alternative water source. If VOC contaminant levels are greater than 10 percent of the MCL, (0.5 �g/L for PCE and TCE) the well will be sampled on a quarterly basis. If VOC contaminant levels are less than 10 percent of the MCL (<0.5 �g/L for PCE and TCE), the well will be included in the group of off-post wells that may be sampled semi-annually. If the second sampling results indicate VOC contaminants at less than 10 percent of the MCL, the sampling frequency may be reduced to annual sampling for two additional years. If after two years of sampling VOC contaminants are not detected, no further sampling will be required.
The off-post groundwater monitoring program was expanded in August 2001 to determine whether other wells in the vicinity of LS-7 were impacted, to ensure that appropriate response actions were taken, and to assist with the assessment of off-post plume migration. This work included the sampling of four additional private and public drinking water supply wells (LS-2, LS-3, LS-5, and LS-6) near the southwestern corner of the post. These wells were all located downgradient of a potential VOC source area identified at Building 90/AOC 65. These well locations are shown on Figure 1.1.
Prior to the September 2001 sampling event, all off-post wells were sampled from existing taps located as close to the wellhead as possible. This enabled the sample to be collected prior to entering the storage tank and minimized chances of VOC volatilization and aeration. Samples were collected after the wells were adequately purged as indicated by stabilization of the pH, conductivity, and temperature parameters. Generally, this required an average of 20 gallons to be purged prior to sample collection from most wells.