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Section 2 - Groundwater Monitoring Procedures
Off-post groundwater monitoring was performed March 1 through 10, 2004. Thirty-two off-post wells were sampled during the March 2004 quarterly monitoring event, and their locations are illustrated 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 wells were recommended for sampling in the December 2003 Off-post Quarterly Groundwater Monitoring Report, and two additional wells were added due to their proximity to well RFR-3 which had a VOC detection in December 2003. Eight post-GAC samples were collected, as well as three samples at Well JW-26 from faucets inside the residence, at the owners� request.
Off-post wells sampled in March 2004 include (see Figure 1.1 for well locations):
| One private well in the Dominion subdivision (DOM-2); | |
| Two public supply well in the Fair Oaks area (FO-J1 and FO-8); | |
| One public well in the Hidden Springs Estates subdivision (HS-2); | |
| Two private wells in the I-10 area (I10-2 and I10-4); | |
| Nine privately-owned wells in the Jackson Woods subdivision (JW-7, JW-8, JW-9, JW-12, JW-14, JW-26, JW-28, JW-29, and JW-30); | |
| Seven wells in the Leon Springs Villa area (four public wells: LS-1, LS-2, LS-3, and LS-4; and three privately-owned wells: LS-5, LS-6, and LS-7); | |
| Privately-owned wells on Old Fredericksburg Road (OFR-1, OFR-2, OFR-3, and OFR-4); and | |
| Six privately-owned wells in the Ralph Fair Road area (RFR-3, RFR-4, RFR-5, RFR‑10, RFR-11, and RFR‑12). |
All wells were sampled from a tap located as close to the wellhead as possible. Most of the taps were installed by CSSA to obtain a representative groundwater sample before pressurization or storage and before entering the water supply distribution system. Water was flushed to engage the well pump prior to sample collection. While the well was pumping, pH, conductivity, and temperature readings were measured and recorded to confirm adequate purging. 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.
Forty-three groundwater samples, four field duplicate samples, two matrix spike/matrix spike duplicate (MS/MSD) pair, and three trip blanks were submitted to APPL Laboratory (APPL) in Fresno, California for analysis. Each groundwater sample collected was analyzed for the short list of VOCs using SW-846 Method 8260. The EPA-approved short list of VOCs analyzed for in off-post groundwater samples 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 which have either been 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 (TO 08 #22, #23, and #24) 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 March 24, 2004 and April 1, 2004, and the data verification reports were submitted to AFCEE on April 9, 2004. AFCEE approved the data packages on April 19, 2004.