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1. INTRODUCTION <br /> • <br /> This document is an Addendum to the Corrective•Action Plan (CAP) originally submitted October S, <br /> ' 2004, developed for affected soil and groundwater beneath the former Continental Grail 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 Geomatnx,Consultants, Inc (Geomatnx) Thus 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 fine]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. BAICKGROUND <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 /> . 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 of the former 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 analyzed 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 /> 1 <br /> R 1CONTGRANIstocktonlCAP\CAP ADDENDUM <br />