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PUBLIC ftEALTH SERVICES
<br /> SAN JOAQUIN COUNTY
<br /> ENVIRONMENTAL HEALTH DIVISION
<br /> Karen Furst M.D. M.P.H. Health Officer
<br /> 304 East Weber Avenue, Third Floor - Stockton, CA 95202 C (aj
<br /> BRETT HUNTER 209/468-3420 OCT 2 71997
<br /> CHEVRON USA
<br /> PO BOX 5004
<br /> SAN RAMON CA 94583-0804
<br /> Re: Ron's Chevron Site Code: 1039
<br /> 139 South Center
<br /> Stockton CA 95202
<br /> San Joaquin County Public Health Services,Environmental Health Division(PHS/EHD) has prepared a summary of recent regulatory
<br /> directives which were issued in response to site conditions encountered during the field investigation which was conducted on October 6
<br /> and 7, 1997 to determine the extent of soil and groundwater contamination which may have resulted from the operation of former
<br /> underground storage tanks. The vertical extent of the contamination was significantly greater than had been previously estimated. As a
<br /> result,PHS/EHD requested that the following samples which were collected at depths below ground surface(bgs),undergo laboratory
<br /> analysis for TPH-gasoline and BTEX;MW8: 25,(30 or 35)and 42 and MW9: 15,20,25,30,35,40,45,50,55, 62,65,70 and 75.
<br /> Additional analysis was requested to investigate the occurrence of oxygenated blending agents utilizing EPA Method 8260 for samples
<br /> collected from MW8 at 30 feet and from MW9 at 25,42 and 62 feet bgs. This site had previously been investigated to a maximum depth
<br /> of 43 feet bgs in the area the former tanks were located and soil contamination of up to 15,000 ppm TPH-gasoline and 160 ppm benzene
<br /> was evidenced.The tanks which were removed in 1990 were installed in the 1970's. The current depth to water is approximately 30 feet
<br /> below grade and has been reported to be as low as 70 feet bgs in 1979(San Joaquin County Flood Control Map).
<br /> The migration of contamination to greater depths than had been anticipated,poses serious risks which have not been explored. The depth
<br /> of the contamination and the lack of information regarding the hydrologic transmissivity of the formation beneath the site,mandates that
<br /> the investigation of the vertically distributed contamination be defined as quickly as possible. Additionally,PHS/EHD has directed
<br /> Chevron to perform EPA Method 8260 to investigate oxygenated blending agents which may have been used during the operation of the
<br /> former underground storage tanks. The two nearest public water wells are within approximately 2500 and 5000 feet of the site and are
<br /> operated by California Water Services.
<br /> As you are aware,PHS/EHD initiated enforcement procedures several times since the unauthorized release was reported,because the
<br /> investigation and remediation was not proceeding in a timely manner. For example,PHS/EHD directed Chevron in correspondence dated
<br /> December 13, 1995,to install the downgradient well,MW8, by May 1996. A corrective action plan was due by December 30, 1997;
<br /> however,so that sufficient information is available to prepare the corrective action plan pursuant to the Health and Safety Code and
<br /> Underground Storage Tank Regulations,PHS/EHD hereby directs Chevron to complete all additional investigation and necessary
<br /> feasibility studies by December 19, 1997 and submit the corrective action plan by January 30, 1998. The report of the results obtained
<br /> during the installation of MW8 and MW9,shall be submitted no later than by November 14, 1997,as agreed and shall include a work
<br /> plan to complete the investigation.
<br /> Chevron has not demonstrated compliance with regulatory directives nor responded cooperatively, costing valuable opportunities to
<br /> remediate the soil contamination while the groundwater was lower and has required extraordinary regulatory staff efforts to continually
<br /> initiate enforcement efforts to motivate Chevron to investigate the extent of the soil and groundwater contamination which resulted from
<br /> the operation of former underground storage tanks. It continues to be PHS/EHD's hope that Chevron's recent efforts will be indicative of
<br /> future compliance with regulatory directives,
<br /> If you have any questions,please do not hesitate to contact me at(209)468-0337.
<br /> Donna Heran,REHS,Director
<br /> Environmental Health Division
<br /> M arYMeaYs,SeniorFHS Marg�gorio,RcEHS V
<br /> Site Mitigation Unit Supervisor
<br /> cc: Pat Anderson,CVRWQCB Mike Camy,California Water Service
<br /> Greg Barclay,Pacific Environmental Group
<br /> A Division of San Joaquin County Health Care Services
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