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1. INTRODUCTION <br /> This document is an Addendum to the Cor-rective Action Plan (CAP) originally submitted October 5, <br /> 2004, developed for affected soil and groundwater beneath the former Continental Grain Elevator (the <br /> site) located at 1805 Harbor Street, in Stockton,California(See Figure 1). Currently, this site is owned <br /> by Penny Newman Elevators. The CAP was originally prepared for ContiGroup Companies, Inc., and <br /> their consultant, Huff& Huff, Inc., by Geomatrix,Consultants, Inc. (Geomatrix). This Addendum to <br /> the CAP has been prepared consistent with the Underground Tank Regulations presented in Title 23 of <br /> the California Code of Regulations by Huff& Huff Inc. for the purpose of assessing three additional <br /> alternatives. The San Joaquin Department of Public Health Services, Environmental Health Division <br /> (PHS/EHD) regulates the site. <br /> Soil and groundwater beneath the site is affected by residual petroleum hydrocarbons following the <br /> permitted removal of a 10,000-gallon underground fuel storage tank (UST) from the site in 1988. This <br /> CAP Addendum contains the technical data and rationale for selecting a corrective action strategy that <br /> is technically feasible and cost effective specifically focusing on excavation alternatives. <br /> 2. BACKGROUND <br /> In January 1988, a 10,000-gallon diesel underground storage tank (UST), which reportedly contained <br /> gasoline, was removed from an area in the southern portion of the site. Analytical testing indicated <br /> detectable concentrations of petroleum hydrocarbon 'constituents in samples collected beneath the <br /> m <br /> farer 10,000-gallon UST. The tank excavation extended to a depth of approximately 14 feet below <br /> ground surface (bgs). Analytical results detpetroleum hydrocarbons total extractable petroleuhydrocarbons (TEPH) at <br /> concentrations of 160 and 24 milligrams per kilogram (mg/kg). No benzene,toluene, ethylbenzene, or <br /> xylenes were detected in the samples. <br /> Table 1 summarizes the chronology of investigative and remedial activities conducted at the site since <br /> 1988. Between 1997 and 2002, ATC Associates Inc. (ATC) advanced soil borings, collected <br /> groundwater samples, and installed monitoring wells at the site. Figure 2 depicts the location of <br /> monitoring wells on site relative to the location of the fonner UST. Samples during this period <br /> contained detectable concentrations of total petroleum hydrocarbons (TPH) as diesel (TPHd) and lower <br /> levels of TPH as gasoline(TPHg), in both soil and groundwater at various locations on the site. <br /> In June 2004, Haley and Aldrich, Inc. conducted a soil and groundwater investigation at the site. The <br /> purpose of this investigation was to delineate the vertical and horizontal extent of petroleum <br /> hydrocarbon impact to soil and groundwater in the vicinity of the former tank excavation area. A total <br /> of 20 soil samples were collected from nine borings and an for TPHd and TPHg. Hydropunch <br /> groundwater samples were collected and one additional monitoring well was installed to complete the <br /> site delineation. <br /> 1 <br /> R:ICONTCjRAN15tock(onlCAl'1CAP ADDENDUM <br />