SITE INFORMATION AND CORRESPONDENCE

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J Former Unocal June 19, 2008 1565 Pacific Avenue Page 2 . Stockton, CA The Work Plan also proposes to collect and analyze water samples at 25, 35 and 45 feet bgs from MW2 using a Snap Sampler but does not explain how this information will be used. There are water sample results from 1988 when the well was installed and water was at about 30 to 35 feet bgs, during the early 1990's when water was at about 45 feet bgs to the current time when water is at 25 feet bgs. The Work Plan proposes to destroy NP-1 by drilling out all the material within the original borehole and grouting it from the bottom up using a tremie pipe and cement-bentonite grout. The EHD approves this method of destruction for NP-1. In the June 19, 2008, letter EHD directed that the ozone.system be placed.back into operation by August 1, 2008 or a work plan be submitted for installation of some other type of wells for feasibility testing of other remedial options by that date since active remediation must be performed to expedite the site clean up so it will be completed within a reasonable time (estimated to be about 10 years). „The Work Plan did not propose installation of some other type of wells for feasibility testing or,even discuss other remedial options being evaluated. The EHD discussed the site and Work_ Plan with the Central Valley Regional Water Quality Control Board on October 15, 2008. Chevron is not in compliance with EHD directives and :has repeatedly been given the directive to modify the ozone system or provide an alternative remedial method since March 21, 2007. The soil vapor probe investigation and the Snap Sampler water sample collection is not approved as adequate and necessary at this time.- Technical justification must be provided for this work. A work plan that includes technical justification and addresses investigation of the previously documented contaminants in the soil and addresses the potential health hazards of direct exposure, vapor emissions and gross contamination and proposes installation of some other type of wells for feasibility testing of other remedial options must be submitted to the EHD within 30 days of the date of this letter. The information from the investigation is to be included in a report on the work that includes a calculation of the remaining mass of contamination in the soil, discussion on whether the remaining soil contamination is a continuing source of contamination to the groundwater as well as discussion on direct exposure, vapor emissions and gross contamination, and a proposal for active remediation of the groundwater contamination. If the work plan is not submitted within 30 days of the date of this letter or does not comply with the EHD directives, this site may be referred to the CVRWQCB for formal enforcement action. If you have any questions contact me at (209) 468-3449. Margaret L gorio, REHS Program Coordinator cc: Jim Barton, CVRWQCB Ms. Helen McCrary, c/o Bank of Stockton, PO Box 1110, Stockton, CA, 95201 David Evans, ARCADIS, 950 Glenn Drive Ste 125, Folsom, CA 95630