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2012 TIDEWATER STOCKTON WORK PLAN FOR SEPARATE PHASE HYDROCARBON REMOVAL <br />AT THE WATERFRONT TOWERS PARKING LOT <br />____________________________________________________________________________ <br />4 <br />2.0 Recommended Remedial Alternative <br />The goal of this workplan is to obtain regulatory concurrence of the conceptual design for <br />removal of SPH in Waterfront Towers parking lot. The proposed remedial approach of product <br />recovery remediation system in this workplan would remove, to the extent feasible, product in <br />groundwater beneath the Waterfront Towers parking lot. <br />During 4Q11, measurable SPH or SPH-sheen was observed in five B-zone wells screened <br />beneath the Waterfront Towers parking lot. SPH thicknesses for these five deep zone wells are <br />summarized below. <br />1 Data collected on December 17, 2011 <br />Due to consistent SPH recovery in the off-site wells in the Waterfront Towers parking lot during <br />quarterly vacuum extraction events, and the recovery rates anticipated with the implementation <br />of a more aggressive remedial system, Stantec recommends installation of specific gravity <br />based active skimmers in MW-50 and passive skimmers in MW-43, MW-47, MW-48, and <br />MW-49. An air compressor will be connected to the active skimmer in MW-50, which will pump <br />air to the skimmer and remove product into a 247-gallon product holding tank via secondary <br />contained tubing. The tubing will have secondary containment with schedule 80 polyvinyl <br />chloride (PVC) piping. The air compressor, holding tank, and associated logic controls and <br />piping will be mounted on a 7 ft by 7 ft skid inside a 10 ft by 14 ft remedial compound. Based on <br />input from WOTOA, the remedial compound will be constructed of concrete masonry unit (CMU) <br />block walls and finished to blend with the existing trash enclosure at the parking lot. <br />Well <br />Identification <br />SPH Thickness1 <br />(feet) <br />MW-43 0.25 <br />MW-47 0.05 <br />MW-48 0.10 <br />MW-49 0.11 <br />MW-50 26.85