SITE INFORMATION AND CORRESPONDENCE FILE 1

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'*Anse ..� MICHAEL D & SHARON OLIVAREZ 300 SOUTH CALIFORNIA Page 2 additional monitoring wells at this site at this time. PHS/EHD considers this proposal to be premature. Groundwater gradient and contaminant distribution can be ascertained accurately by placing one additional monitoring well in a down gradient position, North-easterly, assuming the initial gradient determination is correct. This monitoring well may be placed off site, possibly on the north side of Lafayette Street directly across from the parcel requiring a revokable permit from the City of Stockton or CalTrans. Application in a timely manner to the appropriate agencies will diminish time in processing. Existing monitoring wells should continue to be sampled quarterly. In addition, PHS/EHD staff does not concur with CGI recommendations to perform pump tests at this time, in the event CGI has additional relevant information to support their proposal please submit this information for review. In telephone conversations (September 19, 1995) with CGI and State of California Water Resources Control Board Underground Storage Tank Cleanup Fund (USTCF) staff, PHS/EHD representatives discussed the employment of push point assessment tools for this site recognizing the soil lithology as amenable to such techniques. In short, PHS/EHD recommends that CGI use push point technologies to assess the site with not less than one continuous core in order to determine appropriate locations for future monitoring,vapor extraction, air sparge or air inlet well locations when justified. Push point technology can be economically effective and efficient rapidly generating soil samples, soil gas surveys, and groundwater grab samples while reducing the quantity of boring spoils to be disposed. PHS/EHD recommends mobilization of work crews be minimized to reduce costs. As monitoring well and SVE locations are approved, attempt to organize the installations in one mobilization when possible. PHS/EHD takes this opportunity to remind responsible parties to submit all site work cost estimates included in PHS/EHD approved workplans to USTCF offices for pre-approval prior to initiating work at this site as a means to virtually insure reimbursement. PHS/EHD does not concur with CGI proposals to install vapor extraction wells at this site without further assessment. PHS/EHD recommends that CGI amend its workplan to include proposals for acquisition of geologic and general site data which supports the feasibility of soil vapor extraction (SVE) for this site. This data should include but shall not be limited to, intrinsic permeability of the soil, soil volumes to be treated with mass volume calculations, pore volume calculations, soil structure and stratification (cross-sectional diagrams) from sampling intervals of sufficient frequency, depth to groundwater, moisture content, constituent volatility, estimates of pneumatic conductivity, and rationale for SVE pilot system design. This rationale shall include a design radius of influence with proposals including lateral and vertical spacing of extraction and inlet wells, well head vacuum, pump type and sizing, efficient piping sizing and configurations including appropriate permanently placed instrumentation for system effectiveness evaluation. In proposing this system please take into consideration discharge, monitoring requirements and site construction limitations.