A summary of December 2003 detections above the MCL, below the MCL, below the RL, and increases and decreases for various VOCs since the September 2003 event is included in Table 6-1. 

An average decrease in water levels of 32.85 feet occurred between September 2003 and December 2003.  CSSA had 2.79 inches of rainfall between September 23, 2003 and December 8, 2003.  Rainfall events during the 3‑month period fell mainly in early October and November.  One rainfall event on October 10, 2003 exceeded 1 inch during a 24‑hour period. 

The LGR groundwater potentiometric surface map (Figure 2-1) for December 2003 shows groundwater flow to be variable throughout the facility.  Groundwater flow is to the southwest and south in the southwest corner of the facility.  Flow in other areas of CSSA is generally to the south and southeast, with exceptions 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 south in December 2003. 

Figure 6-1, Figure 6-2, and Figure 6-3 are included for evaluation of the concentrations of PCE, TCE, and cis-1,2-DCE over time in wells where those compounds exceeded the MCLs (CS‑D, CS‑MW16‑LGR, CS‑MW1‑LGR, and CS‑MW2‑LGR).  Concentrations vary greatly over time and show a relatively constant increasing trend over the past 3 years of groundwater monitoring in well CS‑D.  PCE, TCE, and cis-1,2-DCE concentrations in well CS‑MW16‑LGR increased slightly over the past 3 months.  Well CS‑MW1‑LGR concentrations decreased slightly, while CS‑MW2‑LGR concentrations remained constant over the past 3 years. 

Metals were sampled in December 2003 in drinking water wells, and no concentrations were above the appropriate MCL, AL, or secondary standard. 

Vinyl chloride was detected for the first time in one well 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.  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.