SITE INFORMATION AND CORRESPONDENCE FILE 1

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chm Chevron Chevron Products Company 6001 Bollinger Canyon Road September 21, 1998 Building L San Ramon,CA 94583 P.O.Box 6004 San Ramon,CA 94583-0904 Mr. Michael Infutna Marketing—Sales West San Joaquin County Public Health Services Phone 510 842-9500 Environmental Health Division 304 E.Weber Ave.,Third Floor Stockton,CA 95202 Re: Former Chevron Station#94054 2103 Country Club Blvd..Stockton,CA Dear Mr.Infurna: I would like to acknowledge receipt of your letter dated August 18, 1998.Based on your conditional approval of the environmental remediation approach proposed by Tena Vac in their July 15, 1998 Corrective Action Plan(CAP),Chevron will now proceed with CAP implementation. As stated in the August 18"letter,the CAP must be modified to address two requirements.First,the CAP must include an evaluation of at least two remediation alternatives for restoring or protecting groundwater beneficial uses. Second,the CAP groundwater clean-up goals must conform to California MCL's.Chevron would like to point out that all four of the remediation alternatives considered in the CAP do have the potential to achieve MCL's on their own or in combination with intrinsic bioremediation.As such,the CAP did consider at least two alternatives for restoring or protecting groundwater beneficial uses.Unfortunately, the CAP was not clear in presenting Chevron's ultimate clean-up goal(restoring beneficial use).Instead,it proposed an intermediate clean-up goal(SSTL)that would be used for discontinuing active remediation with ultimate clean-up goals being attained after a subsequent period of intrinsic bioremediation. It was later learned that for your agency to approve such a phased remediation approach the first phase would have to be designed and diligently applied to achieve ultimate water quality goals and that any additional phase would be acceptable only after sufficient rationale was provided for discontinuing the fust phase.With this understood,Chevron is prepared to diligently apply air sparging/soil vapor extraction to restore the beneficial uses of groundwater at the subject site. I would also like to acknowledge the concerns raised in your letter about Chevron's ability to effectively monitor groundwater conditions at the site. The third quarter monitoring results indicated the gradient direction is variable and not southerly as suggested by the second quarter data.As such,it appears that the current monitoring well network is sufficient in defining the plume extent.Also as you point out in your letter,many monitoring wells have their screens submerged.Under these conditions relative differences in contaminant concentrations are still evident.As a result,the current sampling information is still useful. Despite the recent increases in groundwater elevation, it is important to note that source area wells MW-1, MW-2,and MW-3 are still effectively screened.Under these conditions,these three wells are still able to provide representative information about groundwater conditions beneath the subject site and about the effectiveness of future remediation efforts. The need for additional wells will be evaluated upon further increases in groundwater elevation. As requested in your August 18'"letter,Chevron is providing the following schedule of remediation activities: