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�•� F Lar r Project 02260.01 November 20, 1990 a The information from the Performance Test was used to determine the capture radius, the distance at which thy: pressure differential created ry by a vacuum pump is measured, in the lateral and vertical planes. The capture radius was noted by recording the vacuum gradient in neighboring probes and wells in inches of water (";120) This procedure was performed at various flow rates at the probr,s and Wills. The detection limit for the vacuum gradient was 0.005" H 0. The effluent from the extraction points was routed through two cylinders in series.; each containing 200 pounds of vapor phase activated carbon. The carbon adsorbs organic vapors from the extraction air stream, preventing discharge of contaminants into the atmosphere. RESULTS Soil Gas Survey TVH concentrations recorded at the probes and wells tested are given in Table 1. The highest TVH concentrations, 31,000 parts per million (ppm), were recorded at monitoring wells 10, 17, and 22 located along the north end of the subject site. TVH concentrations ranged from less than 50 ppm -• to 31,750 ppm. Depths to groundwater varied at the different monitoring well locations tested. All wells with a screened interval of 30 feet or less were dry. Only three of the wells screened at 40 to 70 feet contained water. The depths to groundwater recorded at wells MW-8, MW-15, and MW-16 were 68.5, 68.6, and 68.4 feet below grade, respectively. Performance Test s , The results of the Performance Test are given in Table 2. Vacuum probe extraction volumes ranged from 7.5 to 15.0 standard cubic feet per minute (scfm) with vacuums ranging from 1.5 to 9.5" inches of mercury ("Hg). Extraction volumes rom the monitoring wells tested ranged from 15.0 to f 22.0 scfm with vacuums ranging from 1.0 to 3.0 "Hg. Maximum capture radii of 56 feet in the lateral plane and 50 feet in the vertical plane at the 0 to 30 feet depth interval were noted. There was no vertical influence noted in the 40 to 70 feet depth interval. Groundwater depths were monitored at wells MW-3, MW-8, and MW-10 during the extraction process to determine if localized upwelling was occurring._--____ _ Water level measurements_taken-at-selected-time--intervais-inricate that —_--- -- - —upwelIi did not occur at these wells.