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December 2004 Off-Post Quarterly Groundwater Monitoring Report
Section 2 - December 2004 Groundwater Monitoring Procedures
Off-post groundwater monitoring was performed December 13 through 16, 2004. Thirty-one off-post wells were sampled during the December 2004 quarterly monitoring event, and their locations are shown in Figure 1.1. Off-post wells sampled during this quarterly monitoring event were selected based on previous sampling results and proximity to both the CSSA boundary and wells with detections of PCE and TCE. Public and private supply wells located west and south of CSSA were selected for this event. Table 1.1 illustrates the rationale for selection of wells for sampling based on the Plan and project DQOs. Thirty-two wells were recommended for sampling in the December 2004 Off-Post Quarterly Groundwater Monitoring Report, and one well (HS-1) was not sampled because the well has not been put into service as of the December 2004 event.
Off-post wells sampled in December 2004 include (see Figure 1.1 for well locations):
| Two public supply wells in the Fair Oaks area (FO-J1 & FO-22); | |
| One public well in the Hidden Springs Estates subdivision (HS-2); | |
| Two public wells (I10-2 & I10-5) and two privately-owned wells in the Interstate I‑10 area (I10-4 & I10-7); | |
| Eight privately-owned wells in the Jackson Woods subdivision (JW‑7, JW‑8, JW‑9, JW‑14, JW‑26, JW‑28, JW‑29, and JW‑30); | |
| Six wells in the Leon Springs Villa area (three public wells: LS‑2, LS‑3, and LS‑4; and three privately-owned wells: LS‑5, LS‑6, and LS‑7); | |
| Three privately-owned wells on Old Fredericksburg Road (OFR‑1, OFR‑2, and OFR‑3); and | |
| Seven privately-owned wells in the Ralph Fair Road area (RFR-3, RFR‑6, RFR‑7, RFR‑10, RFR-11, RFR-12 and RFR‑13). |
All wells were sampled from a tap located as close to the wellhead as possible. Most taps were installed by CSSA to obtain a representative groundwater sample before pressurization, storage, or the water supply distribution system. Water was purged to engage the well pump prior to sample collection. Conductivity, pH, and temperature readings were recorded to confirm adequate purging while the well was pumping. Purging measurements are attached in Appendix D. Generally, this required an average of 20 gallons to be purged prior to sample collection. In accordance with the Field Sampling Plan (FSP), adequate purging has occurred when these parameters stabilize.
Thirty-one groundwater samples, three field duplicate samples, two matrix spike/matrix spike duplicate (MS/MSD) pairs, and two trip blanks were submitted to APPL Laboratory (APPL) in Fresno, California for analysis. Groundwater samples were analyzed for the short list of VOCs using SW‑846 Method 8260. The EPA-approved short list of VOCs includes bromodichloromethane, bromoform, chloroform, dibromochloromethane, dichlorodifluoromethane, cis-1,2-dichloroethene (cis-1,2-DCE), trans‑1,2‑DCE, 1,1-DCE, methylene chloride, naphthalene, PCE, TCE, toluene, and vinyl chloride. This list represents analytes that were detected in on-post groundwater samples or analytes which may result from natural degradation of the detected on-post compounds.
The Parsons internal data packages (TO08 #100 through #102) contain the analytical results for this sampling event. Laboratory results were reviewed and verified according to the guidelines outlined in the CSSA Quality Assurance Project Plan (QAPP). Data packages were received by Parsons on January 6, 2005 through January 24, 2005, and the data verification reports were submitted to AFCEE on January 13, 2005. AFCEE approved these data packages January 21, 2005.