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

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, CS‑MW1‑LGR field duplicate, and CS-D.

Monitoring wells CS-4, CS-MW1-BS, CS-MW2-LGR, CS-MW5-LGR, and CS‑MW10-LGR had detections of COCs at concentrations below applicable MCLs but above the RL (Table 6-1).

Monitoring wells CS-2, CS-I, CS-MWG-LGR, CS-MWH-LGR, CS-MW1-CC, CS‑MW2‑CC, CS-MW4-LGR, CS-MW6-LGR, CS-MW6-BS, CS-MW6-CC, CS‑MW7-LGR, CS-MW7-CC, CS-MW9-LGR, CS-MW9-BS, CS‑MW9-CC, CS‑MW10-CC, CS-MW12-LGR, CS-MW18-LGR, and the CS-MW18-LGR field duplicate had no VOC analytes detected above either the applicable MDL or RL.

Drinking water wells CS-1 and CS-9 had no VOC detections in December 2004. Well CS-10 had a detection of chloroform below the RL.

An average increase in water levels of 62.91 feet occurred between September and December 2004. Between September 6, 2004 and December 1, 2004 WS-N reported 20.68 inches of rain and WS-S measured 22.95 inches of rain.

The LGR groundwater potentiometric surface map (Figure 2-1) for December 2004 shows groundwater flow to be variable throughout the facility. Apparent groundwater flow is to the southeast and southwest in the southwest corner of the facility. Flow in other areas of CSSA is also variable, with higher groundwater elevations at the central portion of CSSA. Groundwater extraction from both on- and off-post drinking water supply wells and the pumping at CS-MW16-CC, 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 southwest, and the CC potentiometric surface map near Building 90 indicated a groundwater flow to the east and southeast in December 2004.

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

In December 2004, vinyl chloride was found in wells CS-MW12-BS and CS-MW16-CC. Historical vinyl chloride detections include:

Westbay^� zones that have been historically dry during sampling that were able to be sampled this quarter include: