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"VI � <br /> ASS O C I ATE S I N C . <br /> from approximately 90 to 95 feet bgs. A map showing the proposed locations of the three air <br /> 1 sparge wells is included as Figure 18. <br /> Three air sparge wells will be advanced using a hollow stem auger equipped drill rig to a depth of <br /> 1 approximately 95 feet bgs. Drilling will be conducted by a State-licensed (C57) drilling company. <br /> A field geologist will be present to log drill cuttings and soil samples from the borings. <br /> Descriptions of soil types encountered and sample collection intervals will be recorded on <br /> 1 boring/well logs. Soil samples will be collected at ten-foot intervals. Each soil sample will be field <br /> screened with a photo ionization detector(PID) or similar instrument and at least two samples from <br /> each of the two borings, based on field observations (i.e. odor, discoloration, PID readings), will be <br /> 1 placed in a cooler with ice and submitted for laboratory analyses. <br /> The soil borings will be completed as air sparge wells. The wells will be constructed of 2- <br /> inch inside diameter schedule 40 PVC well screen and casing with approximately five feet of <br /> 0.020 inch slot screened PVC from 90 to 95 feet bgs. To protect the integrity of the wells, <br /> locking, watertight well plugs will be installed on each well and a watertight wellhead labeled <br /> ' "monitoring well" will be concreted over each well. All drill cuttings will be stored on site in <br /> 55-gallon drums pending laboratory results. <br /> Selected soil samples will be immediately placed in a cooler with ice and delivered under <br /> ' chain-of-custody documentation to a State-certified analytical laboratory. The soil samples will <br /> be analyzed for TPHg by EPA method 801513, and BTEX, MTBE, tertiary butyl alcohol <br /> 1 (TBA), di-isopropyl ether (DIPE), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl <br /> ether (TAME), 1,2-dichloroethane (1,2-DCA), and 1,2 dibromoethane (EDB) by EPA method <br /> 8260B. <br /> 1 Similar to the VES, the actual radius of influence for each sparge well will vary and the effective <br /> radius of influence will be evaluated following long-term operation of the AS system. In-situ air <br /> 1 sparging is the process of injecting air into the saturated zone via sparge wells. Sparge wells are <br /> designed with a screen interval at a depth approximately 15 to 20 feet below the water table. <br /> Pressurized air is forced out through the screen and into the saturated zone. The air forms <br /> ' bubbles that rise to the unsaturated zone, carrying trapped and dissolved contaminants. Vapor <br /> extraction wells in the unsaturated zone capture sparged air, which is then treated through the <br /> vapor extraction system. The AS system will include a compressor; associated piping, control <br /> ' valves, pressure gauges, flow meters, instrumentation and controls; and a remediation shed shared <br /> with the VES. Based on ATC's experience at similar sites and the results of the pilot tests, a Gast <br /> 2567-P132-T908X rotary vane compressor would be sufficient to operate the air sparge component <br /> 1 of the system. The compressor would create a maximum of 20 pounds per square inch pressure and <br /> a maximum airflow rate of 18 standard cubic feet per minute. A process and instrumentation <br /> diagram for the AS is shown on Figure 19. <br /> ' 5.2.3 Remediation System Layout <br /> 1 Components of the vapor extraction and air sparge system would be located in an enclosed shed in <br /> the vicinity of the existing on-site shed. A network of subsurface piping will be used to convey off <br /> 1 s:\environmental\21291\reWrls\irp,doc 7 <br />