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INTRODUCTION <br /> r <br /> GHH Engineering, Inc. (GHH) is currently providing Colberg Boat Works (Colberg) with- <br /> it <br /> professional services to assist with environmental services at their site located at 401 <br /> North Stockton Avenue, Stockton, California, as shown on Figures 1 and 2. Ms. Lynn Swanson <br /> of Colberg has authorized GHH to prepare this Additional Assessment Workplan (Workplan) for <br /> the site. This Workplan has been prepared for submittal to the San Joaquin County <br /> k� <br /> Environmental Health Division(County), the lead agency overseeing environmental issues at the <br /> site. <br /> rl <br /> BACKGROUND AND SITE HISTORY <br /> i <br /> Site Description <br /> The subject site is located in the western portion of Stockton, San Joaquin County, California at <br /> an elevation,�of approximately 10-feet above mean sea level(MSL). The site contains several <br /> H service warehouse/storage-type buildings on approximately three acres of land and is <br /> located in an industrial area of Stockton, California. The site is nearly level and is bordered by the <br /> Stockton Deep Water Channel to the south. The site is a former ship yard and with the exception <br /> of limited boat storage, is no longer active. <br /> I� <br /> Summary Of Previous Investigations <br /> On May 16;�1986, Jim Thorpe Oil,Inc. removed two 550-gallon diesel, one 8,000-gallon diesel, <br /> and one 1,000-gallon gasoline under ground storage tanks (USTs) from the site. The area around <br /> the former gasoline UST was over-excavated in 1988. <br /> In February 1993, Telic Engineering Corporation(TEC) of Stockton, California.,performed a <br /> Phase I investigation of the subject site and surrounding area within a 1-mile radius. TEC's <br /> "findings areisunimarized in their report titled Phase I Preliminary Hazardous Materials Site <br /> �jAssessment,dated July 21, 1993. <br /> .On Decem.V6r 12 and 13, 1994, Apex supervised the advancement of 11 subsurface probes to <br /> :collect soil and groundwater samples at the site. Soil and groundwater samples were submitted <br /> j`under chain-of-custody to a state certified laboratory for analysis. Results of the subsurface <br /> investigation are summarized in the report titled Phase II Site Assessment Report dated January <br /> j23, 1995. The results of the subsurface investigation indicated that areas around the'fonn USTs <br /> contained petroleum hydrocarbons. <br /> Subsequently, Colberg was directed by the County to perform further investigations at the site. <br /> This investigation was performed according to Apex's Workplan for Limited Subsurface <br /> I Investigation and Warkplan Addendum for Limited Subsurface Investigation dated May 2; 1995 <br /> and January 24, 1997, respectively, as approved by the County. <br /> 1997 Apex supervised the drilling, soil sampling and installation of six <br /> On July 28,'land 29, , <br /> groundwater monitoring wells at the site at the locations shown on Figure 2. Six soil borings <br /> (SB-1 through SB-6)were drilled and completed as groundwater monitoring wells (MW-1 <br /> �j through MW,:� -6): The soil boring drilling and monitoring well installations were performed by <br /> !I Woodward Drilling Company of Rio Vista, California <br /> F <br /> I�i .. <br />