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George's Service Remedial Action Work Plan Project No.425.2 June 30,2011 6.1.5. Sparge Point As described above, our proposed sparge point will consist of a 24" long fine screened interval designed to produce fine bubbles with maximum surface area. We found that this type of delivery system worked just as well during the pilot test as the more expensive sparge points and has the added advantage of being able to be cleaned by mechanical scrubbing methods if the well becomes bio-fouled. 6.1.6. Air Sparging Equipment The air sparging equipment will consist of a blower/air compressor, controller, manifold, piping, fittings, pressure gauges and distribution valves. Three bids must be solicited for the project in order to stay in compliance with USTCFP requirements. The required injection pressures and flow rates utilized in the sparging system must be sufficient to overcome the head pressure of the overlying water column and the capillary pressure of the subsurface soil. The flow rates must be as high as possible to deliver air to the maximum possible area of the plume. The injection pressures will be lower than the pressures which may cause the lateral spreading of contamination plume. Initially, air will be injected into the subsurface to open up the soil pore space. The pressurized air will be delivered through diffusers that will introduce fine bubbles into the soil. The bubbles will form micro-channels or preferential pathways through which the air will flow. While in the channels the air will allow the gasoline to undergo a phase transfer from dissolved to vapor phase. The system will operate in pulse mode to allow the micro- channels to repeatedly fill and empty which will cause a reaction chamber type response. The increased DO will oxidize the MTBE as well as other constituents and unconsumed oxygen will serve to augment the bio-remediation capacity of the aquifer. The EPA has stated that I PSI of injection pressure is necessary for every 2.3 feet of hydraulic head. (USEPA: How to Evaluate Alternative Cleanup Technologies for Underground Storage Tank Sites, May, 1995). Water Table is at about 12 feet bgs. This would require an injection pressure of 4.4 PSI (10 feet divided by 2.3). 6.2. Low Vacuum Soil Vapor Extraction A low vacuum soil vapor extraction (SVE) is proposed to remove volatile organic compounds from the subsurface by drawing air through the porous gravel excavation backfill area and surrounding subsurface soils. In July, 2009, GTI conducted a soil vapor pilot test to evaluate the feasibility for site remediation using soil vapor extraction technology. A vacuum blower was temporarily attached to VEW-I and run for eight horns. Vacuum pressure draw down was measured in surrounding groundwater monitoring wells, volumetric air flow was measured, emissions were monitored using a portable photo-ionization detector, and vapor samples were collected for laboratory analysis. Geological Tech dcs Inc. 17 4252 RAP.docx