SITE INFORMATION AND CORRESPONDENCE_1985-1997

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Unocal Corporation Diversified Businesses --2000 @row Canyon Place,Suite 400 ifo on Fac sTeleP of eB(510)P867-0760 T/-309 83 5a 'bZNaO�` 14 CAL 76 August 15, 1996 West Region Mr. Michael Infuma Environmental Remediation Services San Joaquin County Public Health Services 304 E. Weber Avenue, 3rd Floor Stockton, California 95201-0388 SUBJECT: Site Code 2162 FORMER UNOCAL SS #5098 5606 Pacific Avenue Stockton, California Dear Mr. Infuma: I received your letter of June 14, 1996 concerning the subject fuel leak case and wish to respond to some of the issues you raise. Your letter indicates that your agency will currently not entertain changes to the quarterly monitoring and sampling schedules. As a result, we have resumed quarterly monitoring and sampling as directed by your office. However, groundwater gradient, flow directions and hydrocarbon concentrations are well established for this site and UNOCAL does not understand the requirement to continue quarterly monitoring and sampling activities for wells MW 10 through MW 15. The hydrocarbon concentrations for wells MW10 and MW 13 through MW15 have historically been non-detect and have historically been elevated for wells MWl l and MW12. Therefore, UNOCAL implemented a semi-annual sampling program for these wells. UNOCAL maintained a quarterly monitoring and sampling program for wells MW 16 and MW 17 during the March 1996 sampling event. This was done as a result of the significant historical data (17 quarters)that already exists for the site and also considers the lack of sufficient data for new wells MW 16 and MW 17. UNOCAL agrees that the changes in sampling frequency should have been approved in advance with your office and we would still like to see a reasonable change to the sampling frequency approved.