Laserfiche WebLink
l <br /> The diameter of the recovery well used in this study was 8 inches, but , well diameter is not <br /> critical to successful implementation of the enhanced vacuum recovery technique. It was <br /> recognized during test design that an 8 inch diameter well would support a multitude of future <br /> options. This well was drilled using an air rotary casing hammer rig to facilitate groundwater <br /> sample collection used to vertically profile the dissolved-phase groundwater contamination. <br /> All observation wells were drilled with a hollow stem auger. The diameter of the observation <br /> wells was 2 inches, and diameter of the existing observation well was 4 inches. Figure 1 <br /> provides a well construction summary for the recovery well. Well constructions and soil <br /> descriptions are similar for the four observations wells. <br /> 2.1.3 Well Head Fabrication <br /> The recovery well was fitted with a specially fabricated head to provide control over the <br /> vacuum pressure inside the well (Figure 2). Vacuum is applied to the recovery well through <br /> a 1 inch diameter PVC stinger incorporated in the well head design. Groundwater is <br /> entrained with air and recovered with the stinger. Because'the lower end of the stinger would <br /> be set below the groundwater surface at start up, a jump start line is incorporated in the <br /> stinger to allow compressed air to be blown down the stinger to clear it of groundwater. This <br /> provides the ability to overcome lift problems associated with a solid stream or slug of water. <br /> Despite its lack of precision, a ball valve was used to control well head vacuum. Availability <br /> and cost were primary consideration for the choice of valve type in this pilot test. A <br /> magnehelic'guage was used to measure vacuum pressure at the well head.. <br /> 2.1.4. Recovery and Treatment Equipment Selection <br /> The RSI S.A.V.E.r''' system was selected for use in the pilot study. This system combines air <br /> stripping, soil venting and combustion technologies and is available as a single off-the-shelf <br /> item (Figure 3). The use of internal combustion (IC) technology for VOC abatement is well <br /> documented by Johnson (1992), Michelson and Roberts (1992), Rippberger (1989) and others. <br /> An examination of the S.A.V.E T'''i system design indicated that the vacuum it generates for <br /> soil venting and air stripping enhancement could be used to recover groundwater. This <br /> represented an untested application for this system. Additional design features that made this <br /> system attractive for the pilot test were its on-board air compressor, 12 volt D.C. alternator <br /> and 110 volt A.C. power converter. The compressor was used to clear the stinger at system <br /> start-up and the electrical take-offs provided auxiliary amenities. <br /> A 500 gallon portable propane tank was selected to fuel the recovery/treatment system for the <br /> duration of the pilot study. It was recognized that a natural gas line could be constructed if <br /> this system were to be included in the long-term remediation program. <br /> The operations of the selected treatment/recovery system predominantly occur under negative, <br /> rather than positive, pressure and because of this the concerns regarding fugitive air emissions <br /> are significantly diminished. Another consideration that influenced the selection of <br /> equipment, that could ultimately be incorporated into the final remediation program, was the <br /> responsible party's (RP's) capability to provide system maintenance, including lubricant <br /> changes, coolant flushes, and engine rebuilds. <br /> 518 <br />