PCE and TCE were detected at F flagged values for the first time from wells CS-I and CS-MW3-LGR.  TCE was detected for the first time in well CS-MW17-LGR and PCE was detected for the first time in CS-MW18-LGR (both F flagged).

Results for cis-1,2-DCE were above the MCL in well CS-MW16-LGR for the first event since September 2003

1,1-DCE was reported in wells CS-1, CS-10, CS-D, CS-MW7-CC, CS-MW16-LGR, and CS-MW16-CC at levels below the RL.  Since similar results were reported in three of the four trip blanks these detections can likely be attributed to field or laboratory contamination.  1,1-DCE is likely not present in the groundwater.

Results for PCE and TCE in CS-4 were below the MCL, after being above the MCL in the June 2004 event.

Methylene chloride was detected in almost all samples, but was also present in all four trip blanks, indicating that this may have been present due to laboratory practices.

MCLs were exceeded for one or more of PCE, TCE, and cis-1,2-DCE, in wells CS‑MW16‑LGR (formerly well CS-16), CS-MW16-CC, CS-MW1-LGR, and CS-D.

Monitoring wells CS-4, CS-MW1-BS, CS-MW2-LGR, and CS-MW10-LGR had detections of COCs at concentrations below applicable MCLs but above the RL (Table 6-1).

Monitoring wells CS-MWG-LGR, CS-MWH-LGR, CS-MW1-CC, CS‑MW2‑CC, CS-MW6-LGR, CS-MW6-BS, CS-MW6-CC, CS‑MW7-LGR, CS-MW9-LGR, CS-MW9-BS, CS‑MW9-CC, CS-MW12-LGR, and CS-MW12-CC had no VOC analytes detected (other than methylene chloride and/or toluene) above either the applicable MDL or RL.

Drinking water wells CS-1 and CS-10 had detections of one or more of PCE, TCE, 1,1-DCE, and chloroform at concentrations below the RL.  Well CS-9 had no VOC detections in September 2004.

An average decrease in water levels of 8.05 feet occurred between June 2004 and September 2004.  Between June 14, 2004 and September 17, 2004 WS-N reported 14.3 inches of rain and WS-S measured 14.57 inches of rain.

The LGR groundwater potentiometric surface map (Figure 2-1) for September 2004 shows groundwater flow to be variable throughout the facility.  Groundwater flow is to the southeast and south in the southwest corner of the facility.  Flow in other areas of CSSA are variable, with higher groundwater elevations at the central portion of CSSA.  Groundwater extraction from both on- and off-post drinking water supply wells, varying rates of recharge from rain events, and the inherent complexity of groundwater flow in a fractured limestone aquifer, all contribute to difficulties in interpreting the potentiometric surface at CSSA.

The LGR potentiometric surface map near Building 90 indicated a groundwater flow to the southeast and the CC potentiometric surface map near Building 90 indicated a groundwater flow to the east and south in September 2004.

Metals were sampled in September 2004 in drinking water wells, and no concentrations exceeded the applicable MCLs and/or AL.

Vinyl chloride was detected for the first time in CS-MW9-BS in December 2002.  During the March 2003 event, seven wells had detections for vinyl chloride.  During June 2003, only CS‑MW1‑BS, CS‑MW1‑CC, and CS‑MW12‑BS had detections of vinyl chloride.  The September 2003 event reported vinyl chloride in three wells (CS‑D, CS‑MW16‑CC, CS‑MW1‑BS).  The December 2003 event reported one detection in well CS‑MW12‑CC.  In June 2004 vinyl chloride was found in one well, CS-MW12-BS.  September 2004 results reported vinyl chloride in wells CS-MW12-BS and CS-MW16-CC.  All detections of vinyl chloride have been below the RL and F‑flagged with the exception of CS‑MW16‑CC in the September 2003 event, which had a concentration of 1.3 μg/L.

Westbay^� well CS-WB02 had two historically dry zones, UGR‑01 and LGR‑02, which had water in them sufficient for sampling.  These zones were sampled for the first time on July 2, 2004.