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I <br /> 1. INTRODUCTION <br /> ' This document is an Addendum to the Corrective Action Plan (CAP) originally submitted October 5, <br /> 2004, developed for affected soil and groundwater beneath the former Continental Gr= 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 Conti Group Companies, Inc, and <br /> their consultant, Huff& Huff, Inc , by Geomat nx,Consultants, Inc (Geomatnx) 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 /> ISoil 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 /> I 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 /> I • former 10,000-gallon UST The tank excavation extended to a depth of approximately 14 feet below <br /> ground surface (bgs) Analytical results detected total extractable petroleum hydrocarbons (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 gf the former UST Samples during this period <br /> contained detectable concentrations of total petroleum hydrocarbons (TPH) as diesel(TPHd and lower <br /> I p ) <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 boxings and analyzed for TPHd and TPH9 Hydropunch <br /> groundwater samples were collected and one additional monitoring well was installed to complete the <br /> site delineation <br /> 1 <br /> t� <br /> I <br /> 1 <br /> ' P,ICONTGRAMStocktoiI%CAP\CAP ADDENDUM <br />