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December 2004 On-Post Quarterly Groundwater Monitoring Report

Section 5 - December 2004 Analytical Results

On-post groundwater sampling was performed November 29 - December 10, 2004. Thirty-three on-post wells were sampled using dedicated low-flow pumps: CS‑2, CS‑4, CS‑D, CS‑MWG‑LGR, CS‑MW1‑LGR, CS‑MW1‑BS, CS‑MW1‑CC, CS‑MW2‑LGR, CS‑MW2‑CC, CS‑MW3‑LGR, CS‑MW4‑LGR, CS‑MW5‑LGR, CS‑MW6‑LGR, CS‑MW6‑BS, CS‑MW6‑CC, CS‑MW7‑LGR, CS‑MW7‑CC, CS‑MW8‑LGR, CS‑MW8‑CC, CS‑MW9‑LGR, CS‑MW9‑BS, CS‑MW9‑CC, CS‑MW10‑LGR, CS‑MW10‑CC, CS‑MW11A‑LGR, CS‑MW11B‑LGR, CS‑MW12‑LGR, CS‑MW12‑BS, CS‑MW12‑CC, CS‑MW16‑LGR, CS‑MW17‑LGR, CS‑MW18‑LGR, and CS‑MW19‑LGR. Six wells, CS‑1, CS‑9, CS‑10, CS‑11, CS‑MW16‑CC and CS‑MWH‑LGR, were sampled using high capacity submersible pumps. One sample was collected from the windmill (CS‑I) that was equipped with a solar-powered submersible pump in September 2003. Samples were collected after field parameters stabilized. For stabilization logs from the In-Situ Rugged Reader see Appendix C.

The analytical program for on-post monitoring wells includes short-list VOC analysis: bromodichloromethane, bromoform, chloroform, dibromochloromethane, dichlorodifluoromethane, 1,1‑dichloroethene (DCE), cis‑1,2‑DCE, trans‑1,2‑DCE, methylene chloride, naphthalene, PCE, TCE, toluene, and vinyl chloride. Samples from the drinking water supply wells (CS‑1, CS‑9, and CS‑10) were analyzed for the full list of VOCs, as well as nine metals. On-post monitoring wells are analyzed for metals once annually. The June 2005 event is the next scheduled annual sampling for metals, including arsenic, cadmium, lead, barium, chromium, copper, nickel, zinc, and mercury. These nine metals and the VOC short list were chosen based on CSSA�s waste disposal records and process knowledge.

Parsons data package numbers TO 0008 #89 through #92 containing the analytical results from this sampling event were received by Parsons from December 16, 2004 to December 21, 2004. Data validation was conducted and submitted to AFCEE on January 12, 2005. AFCEE approved the data packages on January 21, 2005. All detected concentrations of VOCs are presented in Table 5‑1. Full analytical results are presented in Appendix B. Cumulative analytical results can be found in Tables 6 and 7 of the Introduction to the Quarterly Groundwater Monitoring Program (Parsons, 2001) (Volume 5, Groundwater).

5.1 - Volatile Organic Compound Results

5.1.1   Toluene and Methylene Chloride Detections

Methylene chloride has been reported periodically in samples from both on- and off-post wells since 1992. Each time methylene chloride was detected, it was also present in the analysis method blank, indicating the analyte was introduced as a laboratory contaminant and was not present in the groundwater. Methylene chloride is considered a common laboratory contaminant and there are no known historical uses of methylene chloride on-post. Methylene chloride was detected in one sample, CS‑MW16‑LGR (0.24 μg/L F), during the December 2004 sampling event.

Toluene was detected in the December 2004 sampling event at concentrations ranging from 0.29 �g/L to 1.2 �g/L. These levels were below the applicable maximum contaminant level (MCL) for toluene in drinking water (1,000 μg/L). Toluene has been detected sporadically in on-post wells since March 2003.

5.1.2   MCL Exceedances in Monitoring Wells

MCLs were exceeded in wells CS‑MW16‑LGR (formerly well CS‑16), CS-MW16-CC, CS‑MW1‑LGR and CS‑D in the December 2004 event. The detected concentrations are summarized as follows:

Wells in which the contaminants of concern (COC) exceed MCLs were plotted for concentrations over time and are shown in Figure 5-1. Well CS‑MW16‑CC, installed December 20, 2002, does not have results from 1998 through 2002. CS‑MW16-LGR concentrations from the December 2004 event decreased since September 2004. In December 2004 concentrations in well CS‑D decreased and are still below the maximum detection that occurred in December 2003. In December 2004 the concentrations in well CS‑MW2‑LGR continued to decrease while concentrations in well CS-MW1-LGR increased significantly. A remedial process optimization study is currently being conducted for the CSSA groundwater monitoring program. This study will evaluate sampling frequency and analyte lists. The preliminary statistical evaluation will be presented to CSSA in March 2005.

5.1.3   Detections Below the MCL in Monitoring Wells

Additional wells had detections of COCs below applicable MCLs. These wells are monitoring wells installed as part of the ongoing groundwater investigation. Detections of methylene chloride and/or toluene are not discussed as additional information has been provided previously in Section 5.1.1.

Well CS-4 reported PCE and cis-1,2-DCE at concentrations of 1.3 �g/L and 0.93 �g/L, which were below the applicable RL. Also detected was TCE (2.3 �g/L), above the RL. PCE and TCE have been detected in this well since 1992. June 2004 was the first time concentrations have exceeded the applicable MCLs.

Wells CS-MWG-LGR and CS-MWH-LGR reported no VOC detections this quarter. Well CS‑2 also had no VOC detections this quarter. This is the first event for well CS-2 without a PCE and/or TCE detection since March 2003.

CS‑MW1‑BS had a detection of cis-1,2‑DCE (0.25 �g/L), below the RL. Toluene was detected above the RL at a concentration of 1.2 �g/L. This is the first event since September 2003 that TCE has not been detected in this well. Well CS‑MW1-CC had no VOC detections in December 2004.

CS-MW2‑LGR had a detection of cis‑1,2-DCE at a concentration of 3.9 �g/L, above the RL. Well CS‑MW2‑CC was sampled for the seventh time this quarter. The well had no VOC detections in December 2004.

Well CS‑MW3‑LGR reported a detection of TCE for the second time in December 2004, at a concentration of 0.21 �g/L. This concentration was below the RL. Well CS-I reported no VOC detections in December 2004.

CS‑MW4‑LGR reported no VOC detections in December 2004. CS‑MW5‑LGR had detections of PCE, TCE, and cis-1,2-DCE, at concentrations of 1.0 �g/L, 1.6 �g/L, and 1.8 �g/L, respectively. TCE and cis-1,2-DCE were above the RL while PCE was below the applicable RL.

In December 2004 wells CS‑MW6‑LGR, CS‑MW6‑BS, CS‑MW6‑CC, CS‑MW7-LGR, and CS-MW7-CC had no VOC detections. The CS-MW6 cluster has had two occurrences of PCE and/or TCE since the wells were installed in September 2001. The CS-MW7 cluster has had sporadic detections, however PCE and/or TCE has not been detected in these wells since March 2004.

Well CS‑MW8‑LGR had a detection of PCE at a concentration of 0.63 �g/L, below the RL. PCE has been reported in this well since sampling began in June 2001, with the exception of December 2003. All concentrations have been below the RL. PCE was detected for the second time in well CS‑MW8‑CC (0.36 �g/L), below the RL. CS-MW8-CC has been sampled quarterly since June 2001.

Wells CS‑MW9‑LGR, CS-MW9-BS, and CS-MW9-CC had no VOC detections in December 2004.

CS‑MW10‑LGR had detections of PCE and TCE at concentrations of 2.3 �g/L and 0.41 �g/L, respectively. PCE was above the RL but below the MCL while the TCE was below the RL. Well CS-MW10-CC had no VOC detections in December 2004.

Well CS‑MW11A‑LGR was sampled for the seventh time in December 2004. Well CS‑MW11A‑LGR reported a detection of PCE (0.32 �g/L) below the RL. The field duplicate for CS-MW11A-LGR reported the exact same results. Well CS‑MW11B‑LGR reported a detection of PCE at a concentration of 1.1 �g/L, which is below the RL. This is the fifth sample collected from this well since it was installed in June 2003. PCE has been consistently reported below the RL in CS-MW11B-LGR.

No VOCs were detected in CS‑MW12‑LGR in December 2004. CS‑MW12‑BS had detections of naphthalene and vinyl chloride at concentrations of 0.34 �g/L and 0.32 �g/L, both below applicable RLs. CS‑MW12‑CC had a detection of toluene (0.35 mg/L), below the RL.

PCE was detected in well CS‑MW17‑LGR at a concentration of 0.32 �g/L, below the RL. Well CS‑MW18‑LGR reported no VOC detections this quarter. PCE was first detected at a concentration of 0.051 �g/L in September 2004. The field duplicate reported similar results. CS‑MW18-LGR has been sampled quarterly since September 2002. Well CS‑MW19‑LGR had a detection of PCE (0.24 �g/L), below the RL. PCE has been consistently detected below the RL in wells CS-MW17-LGR and CS-MW19-LGR since they were installed in September 2002.

5.1.4   Drinking Water Supply Well Results

Drinking water supply wells are analyzed for the full list of VOCs. Current and former drinking water supply wells for CSSA sampled in December 2004 were CS‑1, CS‑9, CS‑10, and CS‑11. All contaminant concentrations detected in these wells were below MCLs.

CS‑1 had no VOC detections in December 2004. PCE and TCE concentrations have remained constant with sporadic detections of chloroform, methylene chloride and toluene. September 2004 was the tenth consecutive detection of PCE (all F‑flagged), the 21^st consecutive detection of TCE (all F‑flagged), and the first detection of 1,1-DCE. 1,1-DCE was also detected in three of the four trip blanks at similar levels, leading the chemist to believe that these detections can be attributed to field or laboratory contamination, 1,1-DCE is not likely present in the groundwater.

Well CS-9 had no VOC detections in December 2004. There have been five detections of PCE since the well was first sampled in August 1991. All detections have been below the RL. The field duplicate also reported no VOCs present.

Well CS‑10 had a detection of PCE at a concentration of 0.20 �g/L, below the RL. Well CS-11 had no VOC detections.

5.2 - Metals Analyses

All drinking water wells were analyzed for the metals arsenic, cadmium, lead, barium, chromium, copper, nickel, zinc, and mercury in December 2004. In December 2004, no drinking water wells had results above the appropriate MCL, action level (AL), or secondary standard. The next annual post-wide sampling event for metals will be conducted in March 2005.

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