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Subsurface Inveatlgatlon Results <br /> 6131 Pacific Ave., Stockton, CA. <br /> Argis Project No, 90020 <br /> Page 26 <br /> 7.0 RECOMMENDATIONS <br /> The following presents Aegis' recommendations regarding the <br /> further investigation and mitigation of petroleum hydrocarbons in <br /> the subsurface: <br /> 1) Prior to the tank removal activities a work plan was <br /> submitted to the San Joaquin County Environmental Health <br /> _ Department for the installation of three ground water <br /> monitoring wells. The wells are currently scheduled to be <br /> installed the last week of June 1990. The installation of <br /> the wells will be completed as scheduled. <br /> 2) Due to the presence of petroleum constituents in the <br /> subsurface beneath the original tank basin a piping for a <br /> vapor extraction system should be installed concurrently <br /> with the ground water monitoring wells. <br /> 3) Due to the presence of petroleum hydrocarbons in the soils <br /> beneath the product line trenches a horizontal vapor <br /> _. extraction piping system should be laid in the native soil <br /> beneath the product line trenches. <br /> 4) Based on the results of the hydrogeologic investigation a <br /> W report will be submitted detailing the results of the <br /> investigation and discussing the reed for further remedial <br /> activities and/or investigation. <br /> 5) A pilot test for the insitu vapor extraction system will be <br /> permitted through the appropriate agencies and scheduled. <br /> 8.0 PROPOSED WORK PLAN <br /> The following subsections present details of the installation two <br /> proposed test vapor extraction wells and a horizontal vapor <br /> extraction manifold.- Figure 9 presents the location of the wells <br /> •: and the manifold system. Figure 10 presents cross section view of <br /> the vapor extraction system. The vapor wells are located to <br /> t". maximize the effectiveness of the system and to minimize <br /> potential for further migration of petroleum constituents in the <br /> sail. <br /> 8.1?VAPOR WELL INSTALLATION/CONSTRUCTION DETAILS <br /> The procedure for boring installation is referenced in appendix <br /> ! ' A. Sampling is as follows: Soil samples will be collected using <br /> brass liners in a California-modified split-barrel sampler. Soil <br /> Samples will be collected at a maximum vertical spacing of 5.0 <br /> feet and will be screened in the field with a portable <br /> i photoionization detector (PID) or an organic vapor analyzer (OVA) <br /> to determine organic vapor content. Selected soil samples will by <br /> sent to a state--certified-laboratory for analysis. Samples will <br /> be analyzed for Benzene, Ethlybenzene, Toluene, Xylenes (BTEX) , <br /> total petroleum hydrocarbons (TPH) organic mead, and ethyl <br /> i ' <br />