SITE INFORMATION AND CORRESPONDENCE

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r page 2 1196 Louise Ave. The current monitoring well network indicates that the lateral extent of the shallow groundwater contamination has not been defined to the northwest; analytical results from the January 2001 sampling event for MW-1 included 5,300 micrograms per liter (µg/I) total petroleum hydrocarbons as gasoline, and 11,000 µg/I MtBE. The vertical extent of the contaminant plume in the source area appears to be limited to above 65 feet below surface grade (bsg) based on the non-detect analytical results from water samples collected from MW-6, which is screened from 65-75 feet bsg. The lateral extent of the contaminant plume at this depth has not been defined in any direction. Until the full extent of the contaminant plume is known, it is not possible to design a remediation system that could be expected to adequately address it. The work plan states that, "Once the details and costs of the system are completed, CCI will prepare a Corrective Action Work Plan . . . that will include specific details of the proposed groundwater extraction and treatment system for submittal to the County for its review and approval." It is premature at this point to propose preparation of a CAP as the next step without completing the first step, that of defining the extent of groundwater contamination. Before a CAP can be considered and approved for this site, the full extent of the contamination must be defined, as directed in the August 24, 2000 PHS/EHD correspondence. Additionally, PHS/EHD refers Quik Stop to California Code of Regulations, Title 23, Division 3, Chapter 16, Section 2725(d)for a listing of the required elements of a CAP. The CAP must include a feasibility study that evaluates at least two clean-up alternatives for their ability to remediate the contamination and for their cost effectiveness. A feasibility study has not been completed at this site. PHS/EHD hereby directs you to prepare and submit a work plan to complete the investigation of the lateral extent of contamination in both the shallow and deep aquifers. The work plan is due June 4, 2001. After PHS/EHD determines that the lateral and vertical extent of contamination have been adequately defined at the site, discussion of preparation of a CAP may resume. Interim remediation measures that have been attempted at the site include groundwater extraction. Two groundwater extraction events have occurred on site. The first event resulted in purging approximately 1300 gallons of contaminated groundwater and the second event resulted in purging approximately 500 gallons of contaminated groundwater. The stated purpose of the groundwater extraction events was for plume control. PHS/EHD agrees that interim remediation measures may continue at the site while the investigation to define the lateral extent of contamination is completed. If you have any questions, please feel free to call Lori Duncan at (209) 468-0337. Donna Heran, RENS, Director Environmental Services n (.ou Cid t.. Lori Duncan, Senior REHS Dot Lofstrom, R.G. LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit IV cc: Marty Hartzell, CVRWQCB Gary Mulkey, CCI