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March 2002 On-Post Quarterly Groundwater Monitoring Report
Section 1 - Water Level Measurements
Groundwater monitoring scoped under the Air Force Center for Environmental Excellence (AFCEE) 3P/AE Contract 41624-00-D-8024, Task Order 0042, was performed the week of March 11, 2002, at Camp Stanley Storage Activity (CSSA). Groundwater monitoring conducted under this order began at the March 2002 sampling event and will continue through the June 2003 sampling event. Groundwater monitoring conducted prior to March 2002 was conducted under Order 67, DO23, RL74, DO5084, and RL83. AFCEE/ERD and AFCEE/ERC provide technical oversight of the monitoring program.
The current objectives of the groundwater-monitoring program are to determine groundwater flow direction and water elevations, determine groundwater contaminant concentrations for characterization purposes, and identify seasonal variations in physical and chemical properties. Appendix A identifies the data quality objectives (DQOs) for CSSA�s groundwater monitoring program, along with an evaluation of whether each DQO has been attained. The objectives listed in the table also reference appropriate sections of the 3008(h) Administrative Order on Consent. Overall DQOs for the investigations at CSSA are provided in Volume 1-1 behind the RFI Addendum tab (Section 11).
Twenty-nine water level measurements were recorded during the March 2002 monitoring event. Water level measurements were taken in CSSA wells CS-1, CS-2, CS-3, CS-4, CS-9, CS-10, CS-11, CS-16, CS-D, CS-G, CS-H, CS-I, CS-MW1-LGR, CS-MW2-LGR, CS-MW3-LGR, CS-MW4-LGR, CS-MW5-LGR, CS-MW6-LGR, CS-MW6-CC, CS-MW6-BS, CS-MW7-LGR, CS-MW7-CC, CS-MW8-LGR, CS-MW8-CC, CS-MW9-LGR, CS-MW9-CC, CS-MW9-BS, CS-MW10-LGR, and CS-MW10-CC. Transducer data was collected from wells CS-16, CS-MW9-LGR, CS-MW9-BS, CS-MW9-CC, and CS-MW4-LGR. All water levels were measured with an e-line water level indicator. An average groundwater elevation for well FO-20 from the week of March 11, 2002 was obtained from Fair Oaks Water Utilities. Transducer data is discussed in Section 3.0.
Groundwater levels decreased 70.97 feet on average between the last on-post monitoring event, December 10, 2001 and March 11, 2002. This overall decrease was calculated by averaging the groundwater elevation changes for all wells, including those screened across multiple formations. Groundwater depths derived from water level measurements are compared to top of casing elevations and are summarized in Table 1-1. Table 1-2 summarizes the changes in groundwater elevations since the December 2001 event. The current groundwater elevations may be compared to the historical groundwater elevations from October 1992 through the most recent groundwater monitoring event in Table 3 of the Introduction to the Quarterly Groundwater Monitoring Program (Parsons 2002) (Volume 5, Groundwater).
An average groundwater elevation for each unit in the Middle Trinity aquifer is provided in Table 1-1, calculated by using the groundwater elevations from wells screened only in that unit. At CSSA, the Lower Glen Rose overlies the Bexar Shale which overlies the Cow Creek. As indicated on Table 1-1, only those wells screened in a single formation/unit are included when calculating the average water level in each formation. Typically, the water levels measured at CSSA decrease from the Lower Glen Rose to the Bexar Shale to the Cow Creek. The average groundwater elevations in March 2002 for the Lower Glen Rose, Bexar Shale, and Cow Creek were 1077.91 feet, 1064.46 feet, and 1059.27 feet, respectively, a decrease of 71.77 feet in the Lower Glen Rose, 66.9 feet in the Bexar Shale, and 66.36 feet in the Cow Creek from the average levels measured in December 2001. Evaluation of trends in water level elevations in the different units will continue as additional wells are installed.