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1 <br />PFR as '94 C1 :25PM MN.FCR - HRZ.WRSTE <br />EO -1006 <br />Sinclair Oil Corporation <br />F.7 /15 <br />.3- October 9, 1990 <br />An evaluation of the technical feasibility and cost effectiveness of selected remedial alternatives <br />for dealing with contaminated soil has been completed. Consideration was also made regarding <br />the feasibility of installation with respect to on -site land-use activities and operation and <br />maintenance of the remediation system subsequent to start -up. <br />Alternatives considered for soil remediation included: 1) Excavation and thermal treatment of <br />contaminated soil at an off -site facility; 2) excavation and on -site thermal processing; 3) excavation <br />and land spreading of contaminated soils; and 4) in -situ soil venting. The vertical extent of <br />excavation necessary to remediate soils beneath the site, and the location of structures and <br />utilities on the site precludes excavation of soils as a cost effective alternative. Thus, excavation <br />and thermal treatment or land spreading of contamination soils does not appear implementable <br />for this site. Therefore, Braun proposes that a system utilizing in -situ soil venting be <br />implemented. Details regarding the installation and operation of the proposed soil venting system <br />are included in sections 3.0 through 5.0 of this report. Further discussion regarding the <br />alternative remediation systems has not been included in this document, <br />3.0 CORRECTIVE ACTION DESIGN <br />In -situ soil venting is a remediation technique which uses vacuum induced air flow through <br />unsaturated soils to enhance volatilization of liquid phase hydrocarbons and provides a mechanism <br />for the removal of the resulting vapors. This system is particularly applicable in treating coarse <br />grained soils like the poorly graded sands present on site. <br />The depth of contamination encountered at the site will necessitate utilization of a network of <br />vertical vapor recovery wells screened in the contaminated zone. The wells will be installed in <br />a pattern as indicated in Figure 2. Also indicated on Figure 2 is the estimated zone of influence <br />of each vapor withdrawal point. <br />For this site, an appropriate soil venting system is estimated to require a total of three vertical <br />vapor recovery wells installed to a depth of approximately 25 feet below grade. Each well will <br />Page 54 <br />