ARCHIVED REPORTS_SITE CONCEPTUAL MODEL 2009

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amec- 0 June 16, 1988 — November 8, 1988: SVE was conducted at VE-2, near the former TCE storage tanks south of the Decaffeination Building; VE-2 was screened from 10 —25.5 feet bgs. Vapor influent TCE concentrations ranged from 22 to 33 pg/L, then increased to greater than 109 pg/L after one month of operation, before decreasing to non-detectable levels. Approximately 77.6 pounds of TCE were removed during 116 days of operation of VE-2 (RUST, 1994c). • November 8, 1988 — December 5, 1988: SVE was conducted at VE-1, approximately 40 feet west of VE-2; VE-1 was screened from 11 —46 feet bgs. TCE influent vapor concentrations ranged from 4.8 to 8.8 pg/L at this location. Approximately 1.3 pounds of TCE were removed during 13 days of operation of VE-1 (RUST, 1994c). • December 5, 1988—January 5, 1989: SVE was conducted at VE-3, approximately 40 feet east of VE-2; VE-3 was screened from 7 —43.5 feet bgs. TCE was not detected in influent vapor concentrations at this location (RUST, 1994c). • January 1989 —August 1989: SVE was continued at VE-4, where TCE was initially not detected in influent vapor concentrations, but then increased to range between 7.5 to 13 pg/L. Approximately 81.5 pounds of TCE were removed during 230 days of operation of VE-4 (RUST, 1994c). • January 1990 — Late November 1994 (RUST, 1995): SVE was conducted at VE-5, located near the former Chemical Storage Building; VE-5 was screened from 13.5 — 38.5 feet bgs. Chloroform was the primary COC detected in influent vapor, with initial concentrations as high as 2,840 pg/L in influent vapor extracted from this location; vapor concentrations decreased to 55 pg/L by August 1990. Approximately 563 pounds of chloroform were removed over this 115 day timeframe. Scaling of the well screen for VE-5 was an ongoing maintenance problem, and replacement wells VE-6 and VE-7 were installed in January 1992 and October 1992, respectively (VE-7 was the replacement well for VE-6, which also became clogged due to scaling). Operation of VE-6 for 67 days in 1992 resulted in the removal of approximately 28.1 pounds of chloroform; VE-7 operation for 214 days resulted in an estimated removal of an additional 2.3 pounds of chloroform (RUST, 1994c). • October 1992 through 1994: The B-zone monitoring well M-813, located offsite at 519 Stockton Avenue; M-813 is screened from 21 —41 feet bgs, was initially used for SVE, resulting in the estimated TCE vapor recovery of approximately 2.4 pounds for 22 days of operation in 1992. VE-8 was installed nearby and screened from 9—24 feet bgs; SVE was initiated in March 1993 at VE-8. Initial concentrations of TCE were as high as 1.4 pg/L in influent vapor extracted from this location, before decreasing to non-detectable levels (although infrequent detections of TCE vapor as high as 16 pg/L were reported). The mass removal totals calculated for 214 days of operation of VE-8 in 1993 were 0.02 pounds of TCE and 1.4 pounds of chloroform (RUST, 1994c). • 1998, four new SVE wells (VE-9 through VE-12; screened approximately 10 — 26 feet bgs), a vapor monitoring point (OB-1) and a new vapor treatment system were installed to focus vapor extraction activities in the area of highest remaining AMEC Geomatrix, Inc. I:\Doc_Safe\9000s\9837.005\4000 REGULATORY\SCM_01.30.09\1_text\SCM Report Final.doc 14