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San Joaquin County <br /> °U'" Environmental Health Depnartment DIRECTOR <br /> �o P' �f �° M Donna Heran,REHS <br /> 600 East Main Street <br /> PROGRAM COORDINATORS <br /> Stockton, California 95202-3029 Margaret Lagorio,REHS <br /> Robert McClellon,REHS <br /> Jeff Carruesw, REHS,RDI <br /> cq.J P Website: wwW.Sjgov.org/ehd Kasey Foley, REHS <br /> Fba� Phone: (209) 468-3420 <br /> Fax: (209) 464-0138 <br /> October 1, 2009 r <br /> Ms. Catherine Kahler <br /> JM Equipment Co Inc. <br /> 819 S. 9TH St. <br /> Modesto, CA 95351 <br /> Subject: JM Equipment LOP Case#: 9401 <br /> 1245 W. Charter Way CUF#: 12607 <br /> Stockton, CA. 95206 Geotracker ID#: T0607700794 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed <br /> Revised Site Conceptual Model (SCM) dated August 27, 2009 submitted by your <br /> consultant, Geological Technics Inc. (GTI). The SCM is a comprehensive report that <br /> summarizes the history of the site and the former underground storage tank (UST) <br /> usage and was required by the EHD by correspondence dated May 12, 2009. <br /> Included in the •SCM was an evaluation of several active remedial alternatives and <br /> monitored natural attenuation. Each remedial alternative was evaluated for cost- <br /> effectiveness and feasibility. An estimate of time for the contaminant mass to reach <br /> water quality objectives by natural attenuation of the mass was also included. <br /> It was concluded in the SCM that the site qualifies for a "no further action' status for the <br /> following reasons: <br /> 1. The operation of the LISTS at the site was nearly forty years ago (early 1970's) <br /> and the contamination plume has only moved an estimated 58 feet. <br /> 2. The concentrations of the petroleum hydrocarbons in the center of the plume <br /> have not increased. <br /> 3. The concentrations of the contaminants at the perimeter of the plume have <br /> decreased over time and the rate of decrease can be estimated by a first order <br /> decay model. <br /> 4. There are no known sensitive receptors present within 2,000 feet of the plume. <br /> 5. There are no known plans to utilize the groundwater beneath the site within <br /> 2,000 feet of the site for drinking water use. <br /> 6. Natural attenuation of the plume in monitoring well MW-9 would cause <br /> contaminant concentrations to decline and reach acceptable San Francisco Bay <br /> Regional Water Quality Control Board (SFBRWQCB), Environmental Screening <br /> Levels (ESL) in 138 years to 184 years based on different safety factors. During <br /> this time period, the contaminant plume would expand outward approximately <br /> 267 to 356 feet. <br />