SR0084185 (4) - Laserfiche WebLink

Home Browse Search

Geosyntec° consultants 4.2 SVE Well Installation For the installation of the two SVE wells, Geosyntec will contract a California licensed drilling subcontractor that will utilize a Geoprobe® drill to advance the boring. A Geosyntec field team member will oversee the drilling work, log the geology from the soil borings, and ensure that all field activities follow appropriate quality control and applicable regulatory guidelines.The drilling subcontractor will thoroughly decontaminate all equipment between each boring. Each SVE well will be constructed using Schedule 40, 4-inch diameter polyvinyl chloride (PVC) casing. The well screens will consist of 0.020-inch machined slots and will be positioned between 5 and 10 feet bgs in one well and 10 and 20 feet bgs in the other. The placement of the screen for each well will be informed based on the soil boring logs and will span the transmissive sandy interval.A bottom cap will be installed at the end of the screen. A filter pack consisting of#3 sand will be placed six inches below the bottom of the well casing and continue to a depth one to two feet above the top of the screen, followed by two to three feet of bentonite above the filter pack. The remainder of the boring outside the well casing will be backfilled with cement bentonite grout to the surface. Each well will be completed at the surface with a traffic-rated, flush-mounted vault encased in concrete. 4.3 SVE Pilot Test Setup Following installation of the SVE wells,a temporary trailer-mounted SVE system will be procured to conduct the pilot test. Pilot test equipment will include a mobile SVE treatment system trailer with a positive displacement blower, air-water separator knock-out (KO)tank, VGAC vessels for off-gas treatment, and a diesel generator power supply. The approximate layout of the SVE pilot test equipment is shown on Figure 3 and the SVE treatment process flow diagram is presented on Figure 4. Each SVE well will be fitted with a flexible coupling and a 2-inch PVC tee, followed by a 4-foot Schedule 40 PVC header pipe and aboveground 2-inch flexible hose to the inlet of a 160-gallon KO tank. The well head piping will be fitted with a sample port, isolation ball valve, and an averaging pitot tube with a Magnehelic gauge for air velocity measurement. The trailer-mounted blower will be a positive displacement blower rated for 250 standard cubic feet per minute of air flow and up to 14 inches of mercury (in-Hg) vacuum to extract soil vapor from the well.A manual dilution air valve will be used to regulate the vacuum applied to the well. The extracted vapor will first be processed through the KO tank and a small liquid transfer pump will be used to pump condensate accumulated in the KO tank into a temporary 55-gallon drum(s). The extracted vapor will then be processed through up to four 200-pound VGAC vessels filled with virgin coconut shell VGAC and connected in series. The vessels will be connected with 2-inch diameter flexible hose. A 2-inch diameter Schedule 40 PVC stack approximately 10 feet tall will be installed at the effluent of the lag vessel to discharge treated vapor to the atmosphere. The entire setup will be enclosed with a temporary security fence fitted with an acoustic barrier. 4.4 SVE Pilot Test To optimize SVE activities, the pilot test will be initiated in a stepwise manner. The initial step will include a step-rate pneumatic test. The data from the step-rate test will be used to conduct an extended constant rate test, which will then be carried forward for routine operation. The Northern Parking Lot Remedial Plan 7 August 6,2021