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September 2003 Off-Post Quarterly Groundwater Monitoring Report
Section 1 - Introduction
Off-post groundwater monitoring scoped under the Air Force Center for Environmental Excellence (AFCEE) 4P/AE Contract F41624-03-D-8613, Task Order (TO) 0008, was performed September 8-11, 2003. Groundwater monitoring conducted under TO 0008 began with the September 2003 event and continues through the March 2004 sampling event. Groundwater monitoring conducted prior to September 2003 was conducted under several TOs and Delivery Orders (DOs), as shown in Table 1 in the Introduction to the Groundwater Monitoring Program (Volume 5). Up to 40 samples per quarter are funded under TO 0008. AFCEE/Environmental Restoration Directorate (AFCEE/ERD) and AFCEE/Environmental Restoration Consultant (AFCEE/ERC) provide technical oversight of the groundwater monitoring program with the consent of Camp Stanley Storage Activity (CSSA).
The primary objective of the off-post groundwater monitoring program is to determine whether concentrations of chlorinated volatile organic compounds (VOCs) detected in off-post public and private drinking water wells exceed safe drinking water standards. A secondary objective of the off-post groundwater monitoring program is to determine the lateral and vertical extent of the contaminant plumes associated with past releases near Building 90 (Area of Concern [AOC]-65) or from Solid Waste Management Units (SWMUs) B-3 and O-1. A subsidiary objective of the off-post groundwater monitoring program 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 Resource Conservation Recovery Act (RCRA) 3008(h) Administrative Order on Consent (herein referred to as the Order) issued by the Environmental Protection Agency (EPA) on May 5, 1999, to identify and locate both privately- and publicly-owned groundwater wells within ��mile of CSSA. The Offsite Well Survey Report (Parsons, August 2001) was submitted to fulfill this requirement. As part of its ongoing groundwater monitoring program, CSSA extended the sampling of off-post wells beyond the �‑mile boundary required under the Order. Additional background information on locating and identifying off-post private and public water supply wells is located in the CSSA Environmental Encyclopedia (Volume 5, Groundwater). All previously sampled off-post wells are shown on Figure 1.1, including off-post wells sampled during the September 2003 event.
Monitoring of both on- and off-post groundwater is being conducted at CSSA. Selected off-post wells were initially sampled in 1995 and quarterly sampling of off-post wells began in 2001. On-post groundwater monitoring was initiated in 1992 in response to VOC contamination detected in CSSA drinking water supply well CS‑MW16-LGR (formerly named �Well 16�) and continued periodically until the CSSA quarterly groundwater monitoring program for on-post wells was initiated in December 1999. Results from on-post groundwater monitoring are presented in the September 2003 On-Post Quarterly Groundwater Monitoring Report (Volume 5, Groundwater).
The quarterly off-post groundwater monitoring program was initiated in September 2001 in accordance with the Off-Post Monitoring Program and Response Plan (CSSA, June 2002, herein referred to as the Plan). Action levels for detection of VOCs and decisions to sample an off-post well are based on the following:
| If VOC contaminant levels are ≥ 90 percent of the maximum contaminant level (MCL) (≥ 4.5 micrograms per liter [�g/L] based on preliminary data received from the laboratory for tetrachloroethene [PCE] and trichloroethene [TCE]) and the well is used as a potable water source, bottled water will be supplied within 24 hours of receipt of the data, and a confirmation sample will be collected from the well within 14 days of receipt of the final validated analytical report. If the follow-up sampling confirms contaminants of concern (COC) are above 90 percent of the MCLs, the well will be evaluated and either installation of an appropriate method for wellhead treatment or connection to an alternative water source will be performed. Costs related to installation and maintenance of wellhead treatment equipment or connection to an alternative water source will be borne by CSSA. | |
| If VOC contaminant levels are ≥ 80 but � 90 percent of the MCL (4.0 �g/L for PCE and TCE) during any single monitoring event based on preliminary data from the laboratory and the well is used as a potable water source, it will be monitored monthly. If the follow-up sampling confirms that COCs are ≥ 80 but � 90 percent of the MCL, it will continue to be re-sampled monthly until the VOC levels fall below the 80 percent value. | |
| If any VOC COC is detected at levels greater than or equal to the method detection limit (MDL) (historically 0.06 �g/L for PCE and 0.05 �g/L for TCE), and <80 percent of the MCL, the well will be re-sampled on a quarterly basis. This sampling will be conducted concurrently with on-post sampling events and will be used to develop historical trends in the area. Quarterly sampling will continue for a minimum of 1 year, after which the sampling frequency will be reviewed and possibly decreased. | |
| If VOCs are not detected during the initial sampling event (i.e., no VOC contaminant levels above the MDL), further sampling of the well will be considered. A well with no detectable VOCs may be removed from the sampling list. However, if analytical data suggest future plume migration could influence the well, it will be resampled as needed. The well owner, EPA, and the Texas Commission on Environmental Quality (TCEQ), formerly known as the Texas Natural Resource Conservation Commission (TNRCC), will be apprised of any re-sampling decisions regarding the non-detect wells. | |
| For wells where a wellhead treatment system has been installed, post-treatment samples will be collected and analyzed after initial system start-up and at 6-month intervals to confirm the system is effectively removing VOCs. |
A total of 27 off-post wells were sampled in September 2003. A total of 8 samples of groundwater were collected after treatment by the off-site well granular activated carbon (GAC) filtration system. These wells (LS-2/LS-3, LS-6, LS-7, RFR-10, RFR-11, and OFR-3) are sampled twice annually and will be sampled again during the March 2004 event.
An evaluation of the Data Quality Objectives (DQOs) for CSSA�s groundwater monitoring program is presented in Appendix A. The objectives listed in Appendix A also reference appropriate sections of the Order. Overall DQOs for the groundwater investigations at CSSA are provided in Volume 1-1 behind the RCRA Facility Investigation (RFI) Addendum Tab (Section 11). A comprehensive summary of the results from the September 2003 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 3 of this report. Appendix C summarizes pre- and post-GAC unit sampling results. The cumulative historical results, including cations and anions data from off-post groundwater sampling by CSSA, are presented in summary tables located in Volume 5, Groundwater, Introduction to the Quarterly Groundwater Monitoring Program (Table 8 and Table 9). Table 8 presents the Off-Post Groundwater VOC Analytical Results, and Table 9 presents the Off-Post Groundwater Metals Analytical Results. Additional cumulative historical results for off-post wells, organized by neighborhood, are available in Volume 5, Groundwater. The laboratory data packages and associated data validation reports for this sampling event are submitted to AFCEE and CSSA separately from this report. A summary of the objectives and sampling rationale for selection of wells for the September 2003 groundwater monitoring event is included in Table 1.1.