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CLOSURE REQUEST REPORT Section No 2 0 Former American Forest Products Company 07/31/01 2801 West Lane Page 2-1 Stockton,California 2.0 PREVIOUS INVESTIGATIONS 2.1 ENVIRONMENTAL INVESTIGATIONS In February 1985, Bechtel National conducted a preliminary soil investigation, which indicated hydrocarbon impacts in soils adjacent to the two USTs (Bechtel National, 1985) The California Department of Health Services (DHS) required the preparation of a Remedial Action Plan (RAP) for the site during September 1986 Between June and September 1987, J H Klemfelder conducted a soil and groundwater investigation at the site (Kleinfelder, 1987) The purpose of the investigation was to further characterize the extent and type of petroleum hydrocarbons identified in the soils by Bechtel National and evaluate any potential adverse impact on groundwater resulting from the presence of the petroleum hydrocarbons in the vicinity of the maintenance shop (Figures 2 and 3) DHS assigned the San Joaquin County PHS-EHD in April 1988 to be the lead agency for the site and stated that a final cleanup report was required Also in April, AFPC contracted Dames & Moore (now known as URS) to review existing data and perform a supplemental site investigation in the maintenance shop area Dames & Moore received approval from the PHS-EHD for their proposed investigation in May 1988 On May 11, 1988 the two USTs were gated and removed under the supervision of the PHS-EHD Also during May 1988, a soil investigation was conducted by Dames & oore ase partially on the results of the soil investigation, a Feasibility Study/Remedial Action Plan (FS/RAP) was submitted to PHS-EHD by Dames & Moore in July 1988 (Dames & Moore, 1988) The FS/RAP recommended the demolition of the shop to access impacted soil and excavation of soil with TPHd concentrations >10,000 parts per million (ppm) The site restoration proposed included capping the excavation area with asphalt, and treating TPH-impacted soil on site with bioremediation techniques PHS-EHD stated in a letter in November 1988 that the FS/RAP submitted by Dames & Moore in July was adequate and granted conditional approval However, PHS-EHD stated that three issues needed to be addressed, including identification and sampling of three on-site production wells and three monitoring wells, identification of(production) wells in the vicinity, and possible adjustment of well placement In Iate November, Dames & Moore submitted a response and a modified work plan addressing the issues stated in the PHS-EHD Ietter Dames & Moore subsequently submitted a revised work plan in January 1989 to PHS-EHD that included changes in analytical procedures In the Letter Report — Groundwater Monitoring (Dames & Moore, 1989), Dames & Moore stated the desire to proceed with the proposed remediation in accordance with the November 1988 conditional approval from PHS-EHD In September 1989, PHS-EHD requested that AFPC choose one of two options for further action (1) continue site investigations, or (2) follow guidelines of Tri-Regional Staff Recommendations and the Leaking Under- ground Fuel Tank(LUFT)document In addition, PHS-EHD referred site management back to DHS In February 1990, the RWQCB agreed with the proposed plan of excavation and on-site treatment, combined with long-term monitoring The RWQCB required preparation and submittal of a detailed work plan for soil removal and a long-term monitoring plan, including new monitoring wells A Soil Remediation and Groundwater Monitoring Workplan detailing the implementation of recommendations outlined in the FS/RAP was submitted to PHS-EHD and RWQCB in April 1990 (Dames & Moore, 1990a) During June 1990, soil excavation was conducted in the area of the two former USTs, and the mainte- nance shop was demolished Excavations were completed to ZJfcaLbz1QmLg=de at the former 10,000- K 1840191afp`afp_c1osure_rpt doe