ARCHIVED REPORTS_CONCEPTUAL SITE MODEL

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exists between the Upper A zone and the A zone aquifers beneath the site. Results of the constant-rate aquifer pumping test performed in the A zone determined this aquifer could sustain a pumping rate of 9.25 gpm. Drawdown was observed in monitoring wells located up to 60 feet away from the pumping well at a pumping rate of 9.25 gpm. An average value of approximately 294 square feet per day and 0.41 was estimated for average transmissivity and specific yield, respectively. Based on the A zone saturated thickness of 20 feet, the average hydraulic conductivity estimated was 15 feet per day (0.0052 centimeter per second). The zone of influence of the pumping well was calculated to be 264 feet. This was confirmed by the drawdown data observed in monitoring wells during the pumping test (SECOR, 2003c). • In July 2003, a Feasibility Study Report and Site Assessment Work Plan was submitted presenting a discussion of the objectives of the feasibility study, site background, description and evaluation of each remedial action alternative, potential impacts of each remedial action, estimated costs and project schedule for each remedial alternative, preferred alternative (groundwater oxygenation) and a work plan for additional site assessment activities (SECOR, 2003d). • On September 3, 2003, 12 offsite soil borings (C-3.5, C-4.5, C-6, C-8, D-4, D-5, D-6, D-9, F-9, H-9, J- 8, and K-8) were advanced with a hand auger. Discrete soil samples and grab groundwater samples were collected from each location. The purpose of the offsite assessment was to further delineate petroleum hydrocarbons in groundwater and soil along the northeastern and northwestern site perimeter. The results and discussion of these activities were reported in the 2003 Offsite Assessment Report (SECOR, 2003e). • On September 4, 2003, offsite groundwater monitoring wells MW-53A, MW-57A, MW-58A, and MW- 59A were destroyed. Monitoring wells were destroyed in accordance with SJC-EHD well standards for well destruction. The results and discussion of these activities were reported in the Third Quarter 2003 Quarterly Groundwater Monitoring Report(SECOR, 20030. • In October 2003, a Cleanup Plan was submitted presenting a discussion of the objectives, site background, nature and extent of contamination, a conceptual design of the selected remedial alternative, and a project schedule for implementation of the selected alternative (SECOR, 2003g). • On December 11, 2003, as groundwater monitoring well MW-68A was installed within the former transmix UST location. Groundwater monitoring well MW-68A was advanced to a total depth of 41.5 feet bgs (SECOR, 2004b). • Between May 3 and 7, 2004, approximately 775 cubic yards of soil impacted with petroleum hydrocarbons were excavated. The objective of the excavation was to remove hydrocarbon mass from the former Keylock area and reduce aqueous phase hydrocarbons onsite. During the excavation, twelve soil samples were collected at approximately 5 feet bgs and submitted for chemical analysis. Soil analytical results and field observations indicate that impacted soil in the Keylock area located near the southeastern property boundary was removed during the excavation activities. Results of the soil samples collected along the sidewalls of the excavation were below risk-based screening levels (RBSLs) set forth in the technical document entitled Application of Risk-Based Screening Levels and Decision Making to Sites With Impacted Soil and Groundwater prepared by the CRWQCB - San Francisco Bay Region (SECOR, 2004C). • Between November 18 and 19, 2004, 16 offsite soil borings (A-8-1, B-8-1, B-9-1, C-3,5-1, C-4,5-1, C- 6-1, C-8-1, D-4-1, D-4,5-1, D-6-1, D-9-1, F-9-1, H-9-1, J-8-1, J-9-1 and K-8-1) were advanced with a BLASLAND, BOUCK &LEE, INC. 312/06 engineers,scientists,economists 2-4 J:\D0006\44634_00161022_Conceptual Site Model.doc