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1 <br /> 1 334 Remedial Actions <br /> 1 3.4.1 Soil Remediation <br /> USTEC began preparation for in-situ remediation of the impacted soil beneath the site by <br /> completing borings B-14 through B-17 and B-25 through B-28 as vapor wells VEW-1 through <br /> ' VEW-8 to depths ranging from 28 to 68 feet bgs (Figures 2 and 3) Wells VEW-1 to VEW-4 <br /> I <br /> were installed in October 1990, and wells VEW-5 to VEW-8 were installed in November <br /> 1 1991 The borings for the vapor extraction wells were drilled using 10-inch hollow-stem <br /> augers The vapor extraction wells were constructed using 4-inch Schedule 40 PVC well <br /> 1 screen with a slot size of 0 010 inches Well construction details are presented in tables <br /> prepared by USTEC contained in Appendix A <br /> In November 1990, USTEC conducted a preliminary vapor extraction test to determine the <br /> feasibility of using vapor extraction as a soil remediation alternative (USTEC, September <br /> 1 1991) The test was conducted on VEW-1 through VEW-4 and MWA, MW-4, and MW-5 <br /> Applied wellhead vacuums ranged from about 50 to 66 inches of water Induced vacuums in <br /> the observation wells were measured, and ranged from 0 1 to about 6 inches of water <br /> Distances between extraction and observation wells ranged from 12 5 to 94 5 feet <br /> ' Concentrations of extracted soil vapors were not determined, nor was the effective radius of <br /> influence <br /> 1 In November 1992, RESNA conducted a soil vapor extraction test at the site on the eight <br /> existing wells Laboratory results indicated that TPHg vapor concentrations ranged from 33 <br /> 1 mg/m3 to 19,000 mg/m3 Test flows ranged from 26 2 to 109 cubic feet per minute (cfm) at <br /> applied vacuums of 10 to 100 inches of water column <br /> 1 <br /> 3.4.2 Remedial Action Plan and Addendum <br /> ' In September 1991, USTEC prepared a Remedial Action Plan (RAP) for submittal to <br /> PHS/EHD The RAP included a summary of previous investigations, results of the vapor <br /> 1 extraction pilot test, and a conceptual remedial system design In March 1993, RESNA <br /> prepared an addendum to the RAP for soil remediation at the site Soil vapor extraction was <br /> determined to be a viable alternative for remediation of soil at the site It was recommended <br /> that the vapor extraction system would bring three wells on line The estimated radius of <br /> n 10540061reportslCLO1195 doc 7 <br /> • <br /> 1 <br /> SMITH <br />