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1 , LUVIAa-6970D Cow, our gma ,�tja�&ww W ,a„ bnao.,, aray hk Concentrations of ME and other VOC COOS managed below the ground water cleanup standards in all Easters GSA Consensus and monitor wells from July 2005 to February 2012 (6 years and 8 months), including throughout the five-year pod-shntdown moniloringp niod, with one exception (Figure 4). the historical maximum VOC CDC umcentations and the maximum at the time monitoring crossed in 2012 in Eastern GSA ground water compared to the ground water MCL cleanup standards are presented in Table 3. TCE was detectal only once above cleanup standards during the five-year post shutdown monittiring period, (6.9 pgl in well W-26R-01, in May 2009) (Figure 5). This well and nearby well W-26R-04 were Vesampled in June 2009 with no ICE detections above the cleanup standard. These results were discussed with EPA, DTSC, and RWQ03 at the July 8, 2009 RPM Meeting. The regulatory agencies concurred with continued monitoring and evaluation of ICE in Easters GSA w MEells to detemnine if ICE concentrations were rebounding. E concentrations cammashaderse _re below the 5 ag/L cleanup standard in all samples Jam well W-26R-01 between now 2004 up until the May 2W9 sampling event, and between June 2009 (aaer the May 2009 sampling event) and January 2012. Became of these data from well W-26RID, coupled with the fact that no similar increases were observed in other Eastem GSA wells at (his time, the May 2009 ICE concentration in well W-261141 is constricted ro be an anomalous data point. Time-senes immncentmtion contour maps of triehlomemene (ME) in ground water in the Eastern GSA (fur years 1990, 2000, 2005, and 2012 is shown in Figure 6. ME concentrations decreased from a historical maximum concentration of 71 µg/L in DKQ to a is quarter 20I2 maximum of3.2 pg/L. TCE concentrations art below both the 5 pg/1. MCI, cleanup standard and the 0.5p8/L analytical caroming limit in 32 of the 42 Eastern GSA wells. ME concentrations in the other 10 of42 Eart an GSA wells are above the reporting limit, but below [be 5 End, cleanup standard (Eigme l). WE concentrations in these 10 wells have been Mow the cleanup standard for 5 years or more and are continuing to decline to below the 0.5 pg/L analytical reporting limit (Table 4). ICE has not been derected in any oli'site wells above the 5 pg/L cleanup led n 12 ro 20 years. Concentrations of the other VOC contaminants of concern, that included is-1,2-DCE, bamodirLloromeaanq chlomfnrm, and PCN are ail hems the 0.51t/L analytical reporting limit and their MCI. cleanup standards in Eastern GSA ground water (fable 3). Samples have been collects from whale sense water-supply wells CON and CDPI, located dowagmdmin ofthe Eastem GSA debris burial Imnchw% since 1992 and 1987, aspectivcly. ME has not been detected at concentrations above the reporting limit in she 475 samples collwad from waser-supply well CONI since 1982. ICE was detected twice at concentrations above the reporting limit in the 457 samples collects G me am wrsupply well CDFI since Fully.9 The maximum TCE concentration detects in these Ewa samples was 0.6 µ/t. in a duplicate sample collected from CDFI on September 13, 1995 (ME was not deteced In the mount: sample collected the same day). ICE has not been detected in any of me 363 monthly samples reliectcd from CDFI since the September 1995 detection. 5. Summary of Operation and Maintenance There are no remaining operation and maintenance activities to be paramted. The demolition of the Eastern GSA ground water returning and treatment facility and Fasters GSA ground water extraction and monitor wells will be scheduled allowing regulatory concurrence that terminators