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Ma <br /> µ'M <br /> sy <br /> ADOQMUM 70 9)-TANK WE ASSM A DfT Y10FOG'LAN," <br /> 7 March 1991 <br /> Page 3 <br /> o In order to address the impacted soils below the proposed tank <br /> � basin, the installation of two 12 inch Schedule 80 PVC sumps <br /> a will be installed, during construction, within the new tank <br /> basin as shown on Figure 1 and Figure 2; <br /> o One 12 inch sump will be located in the known impacted area <br /> ' along the north side and between two of the proposed tanks. <br /> The remaining 12 inch sump will be located in the southern <br /> half of the new UST'sFi <br /> ( gore 2) ; <br /> a Access to the sumps will be through a traffic box set flush <br /> with the new concrete pad. Upon completion of the UST <br /> installation, two vapor extraction wells will be constructed <br /> ` g within the sumps according to Exxon's and SJCPHSD's <br /> F„l requirements. The vapor extraction well depths, construction <br /> will be determined in future workplans; <br /> o A 30 mil Oil Resistant PVC plastic tarp, lining the new tank <br /> basin, will act as a vapor barrier between the porous tank <br /> .,, basin backfill material and the native soils (Figure 2) . This <br /> will allow for vapor flow to occur mainly in the native soils <br /> below the proposed tank basin; <br /> `" a The Typar Filter Fabric will protect the plastic tarp from <br /> tear that could occur during backfilling and.installation of <br /> the new UST's (Figure 2) ; <br /> The manage`nent of the stockpiled soil generated during removal of <br /> + the existing UST's and extended excavation for the proposed UST's <br /> is as fol,'.ows: <br /> o During excavation the soil will be segregated by utilization <br /> of a field screening device. The soil will be temporarily <br /> stockpiled on site and placed on and covered with plastic. <br /> The volume of soil is suspected to be approximately 650 cubic " <br /> ! ` yards; <br /> o Based upon field readings, the soil will be sampled according <br /> to the San Joaquin County Air Pollution Control District. The <br /> samples will be sent, under chain-of-custody, to a state- <br /> certified laboratory for the specified analyses; and, <br /> oUpon receipt of the._.labo.r.atory__.re..sults__r4port.,_the._soil_will— <br /> -- be treated accordingly and disposed of at an Exxon approved <br /> landfill. <br /> 9o-2=,LTR <br />