ARCHIVED REPORTS_SITE CONCEPTUAL MODEL 2009

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amec- 3.1.3 Detections of COCs in Plant Production Wells Nestle collected groundwater samples from production wells N-1 and N-2 for analysis of VOCs in January 1986. The sample from well N-1 was reported to contain the following VOCs (RUST, 1994a): • TCE at a concentration of 638 micrograms per liter (pg/L) • Trans-1,2-dichloroethene at a concentration of 2.5 pg/L • Tetrachloroethene (PCE) at a concentration of 0.1 pg/L • Chloroform at a concentration of 0.5 pg/L With the exception of 1,2-dichloroethane (1,2-DCA)which was not detected at the unspecified detection limit; no other VOCs were analyzed. The sample from N-2 was also reported to contain VOCs, but these results were not published in RUST (1994a). After detecting VOCs in the sample from well N-1, the well was not operated until a granular activated carbon (GAC) treatment system was installed for removing VOCs from groundwater pumped from N-1 prior to TDS treatment. Well N-1 was restarted in June 1986 and pumped at a rate of approximately 140 — 150 gpm for plant use until the plant closed in late 1994. 3.1.4 Remedial Investigations After VOCs were reported in the groundwater sample from N-1, six phases of remedial investigations were completed: • Phase 1 (1986): seven monitoring wells (M-1 A, M-1 B, M-2A, M-213, M-3A, M-313 and M-4) and three vapor/groundwater extraction wells (VE-1, VE-2, and VE-3) were installed onsite (Figure 3). The highest COC concentration reported for samples from these wells in January 1987 was 7,100 pg/L for TCE from well M-1A (constructed with screen from 101 — 121 feet bgs); TCE concentrations ranged from non-detect to 52 pg/L in groundwater samples from the other monitoring wells. • Phase 2 (1987): A soil vapor survey was conducted that included collecting 63 soil gas samples (presumably at a depth of five feet bgs although the depth was not reported in RUST, 1994b) at different locations onsite and offsite for analysis of TCE, trichloroethane (TCA) and PCE with a mobile gas chromatograph. The major COC detected was TCE with the highest concentration reported at 54 lag/L near a location "where TCE was handled and used", near the former Decaffeination Building, and 6 lag/L, west of the Decaffeination Building, near Industrial Avenue. Four offsite monitoring wells (M-5A, M-513, M-9A and M-913) and two onsite vapor extraction wells (VE-4 and VE-5) were installed. A groundwater sample was collected from vapor extraction well VE-4 and reported to contain TCE at a concentration of 2,100 lag/L; VE-4 is near the north side of the Decaffeination Building. TCE was not detected in the groundwater sample from VE-5 near the AMEC Geomatrix, Inc. hDoc_Safe\9000s\9837.005\4000 REGULATORY\SCM_01.30.09\1_text\SCM Report Final.doc 10