[Home]
[Table of Contents] [Next Section]
March 2002 Off-Post Quarterly Groundwater Monitoring Report
Section 1 - Introduction
Off-post groundwater monitoring scoped under the Air Force Education Training Center (AETC) Contract F41689-96-D-0710, Delivery Order (DO) 5084, was performed during the week beginning March 18, 2002. Groundwater monitoring conducted under this delivery order began in September 2001 and continues contractually through the June 2002 sampling event. Twenty samples per quarter are funded under DO 5084. Additional samples are funded under AMC Contract number F11623-94-D0024, RL83. Air Force Center for U.S. Environmental Excellence/Environmental Restoration Directorate (AFCEE/ERD) and AFCEE/Environmental Restoration Consultant (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 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 plume associated with past releases near Building 90 (Area of Concern [AOC]-65) or from Solid Waste Management Unit (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 Resource Conservation Recovery Act (RCRA) 3008(h) Administrative Order on Consent issued by the Environmental Protection Agency (EPA) on May 5, 1991, to identify and locate both privately and publicly-owned groundwater wells within �-mile of CSSA. As part of its ongoing groundwater monitoring program, CSSA has extended the sampling of off-post wells beyond the �-mile boundary required under the Order. The Offsite Well Survey Report (Parsons, August 2001) was submitted to fulfill this requirement. 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 off-post wells sampled in the past are shown on Figure 1.1, including off-post wells sampled in the March 2002 event, and off-post wells sampled on a monthly basis in January and February 2002.
Action levels for detection of VOCs and decisions to sample an off-post private well are based on the following:
| If VOC contaminant levels are ≥90% of the MCL based on preliminary data received from the laboratory (≥4.5 �g/L for PCE and 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. The re-sampling will take place within 14 days of the receipt of the final validated analytical report. If the follow-up sampling confirms contaminants of concern are above MCLs, the residence or supply well will be evaluated and an appropriate method for wellhead treatment or connection to an alternative water source will be determined. Cost related to the 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% of the MCL during any single monitoring event based on preliminary data from the laboratory (4.0 ppb for PCE and TCE) and the well is used as a potable water source, it shall be monitored monthly. If the follow-up sampling confirms contaminants of concern are ≥80% of the MCL, it will be re-sampled until the level falls below the 80% value. Should the value be ≥90% of the MCL see above. | |
| If any VOC contaminant of concern (COC) is detected at levels ≥the MDL (historically 0.11 �g/L for PCE and 0.14 �g/L for TCE), and <80% 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 one 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 would be considered on an as needed basis. A well that has no detectable VOCs can be removed from the sampling list, unless plume migration could influence the well. The well owner, EPA, and TNRCC will be apprised of any re-sampling decisions regarding the non-detect wells. |
Action levels for detection of VOCs and decisions to sample an off-post public well is based on the following:
| When off-post public supply systems are ≥90% of the MCL, CSSA will coordinate solutions to the maximum extent practicable. The system operator and CSSA will determine the best course of action for providing potable water when data suggests an exceedance of the MCL. Possible options include: | |
| Potable water could be brought in by tanker truck. | |
| Potable water could be provided by adjacent water systems. | |
| A wellhead protection system (GAC) will be installed by CSSA. |
Results from seven wells (LS-6, LS-7, RFR-10, RFR-11, LS-2, LS-3, and OFR-3) identified VOCs at concentrations greater than 90 percent of their respective MCLs, as presented in Section 2.0 and Section 2.1. This prompted CSSA to install GAC treatment systems on these wells to reduce contaminant levels in the water supply to safe levels. In August 2001 GAC systems were installed at wells LS-6 and LS-7. In October 2001 GAC systems were installed at wells RFR-10 and RFR-11. In April 2002, GAC systems were installed for wells LS-2, LS-3, and OFR-3. These wells are further discussed in Section 4.0 and Section 5.0 of this report. Operation and maintenance (O&M) of the systems are performed by CSSA on a periodic basis. The action levels for VOCs are based on the MCLs established by the EPA under the Safe Drinking Water Act. The �greater than 90 percent of MCL� action level complies with the Plan developed by CSSA and finalized in July 2001. Pre- and post-GAC samples have been routinely collected during the quarterly sampling events and were collected from LS-6, LS-7, RFR-10 and RFR-11 during the March 2002 sampling event. Post-GAC samples were collected in April 2002 from LS-2/LS-3 post-GAC and OFR-3 post-GAC. Post-GAC sample results indicate that all GAC treatment systems are effectively reducing or eliminating contaminants from the respective wells. There were no detections of VOCs from the Post-GAC sample results.
The total number of private wells sampled in March 2002 was 24, scoped under the current funding mechanism (AETC Contract F41689-96-D-0710, Delivery Order 5084). Post-GAC samples for LS-2, LS-3, LS-6, LS-7, OFR-3, RFR-10, and RFR-11 were sampled under AMC Contract F11623-94-D0024, RL83. Due to increasing detections of COCs in some off-post wells, additional monthly sampling events were necessary to track concentrations of the detected contaminants and confirm the wells remain safe to use. Per the Plan, additional samples were collected from selected off-post wells LS-2, LS-3, and OFR-3 between quarterly sampling events from December 2001 to March 2002. These additional monthly sampling events were funded under both RL83 and DO 5084.
An evaluation of whether the Data Quality Objectives (DQOs) for CSSA�s groundwater monitoring program were attained are presented in Appendix A. The objectives listed in Appendix A 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 March 2002 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 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. The laboratory data packages and associated data validation reports will be submitted to AFCEE and CSSA separately.
A summary of the objectives and sampling rationale for the selection of wells for the March 2002 groundwater sampling event is included in Table 1.1.