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' influence for this proposed system was adequate to cover the area of concern The proposed <br /> design flows were 75 cfm per well at a vacuum of 60 inches of water column <br /> San Joaquin County Public Health Services approved the RAP addendum in May 1993 <br /> 3.4.3 Remediation System Operation and Maintenance <br /> ' RESNA installed a vapor extraction system (VES) at the site in June and July 1993 to remove <br /> petroleum hydrocarbons from soil beneath the site The VES was constructed under Authority <br /> ' to Construct No N-2568-2-0 and consists of Airex Corp Model Retox 600 Thermal Oxidizer <br /> with a 40hp blower, knockout drum, three vapor extraction wells (VEW-2, VEW-3, and <br /> ' VEW-7), underground piping, and associated electrical and instrumentation (RESNA, March <br /> 1993) The layout of the vapor extraction system is presented on Figure 5 Wells VEW-2, <br /> VEW-3, and VEW-7 are screened from 8 to 28 feet, 8 to 30 feet, and 8 to 30 feet bgs, <br /> ' respectively The VES began operating on July 23, 1993 An inspection was performed by <br /> San Joaquin Valley Unified Air Pollution Control District who subsequently issued a Permit to <br /> Operate (PTO) The system was monitored weekly in accordance with the conditions of the <br /> PTO In December 1993, a modification to the PTO was approved to reduce monitoring to <br /> ' bimonthly In addition, VES influent and effluent vapor samples were collected for laboratory <br /> analysis of total petroleum hydrocarbons as gasoline (TPHg) and benzene, toluene, ethyl <br /> benzene, and xylenes (BTEX) The vapor extraction system has removed over 3,700 pounds <br /> of petroleum hydrocarbons from soil beneath the site (Smith Environmental, May 1995). The <br /> system was shut down in Apnl 1995 due to electrical problems The extraction rate at that <br /> time was less than one half pound of petroleum hydrocarbons per day The system was not <br /> restarted in anticipation of site closure A summary of analytical data and emission and <br /> ' extraction rates is presented in Table 5 <br /> ' 3.4.4 Groundwater Remediation <br /> Due to the relatively low levels of dissolved petroleum hydrocarbons detected in the <br /> 1 groundwater, active groundwater remediation was not initiated at the site Natural <br /> biodegradation of petroleum constituents was monitored by conducting quarterly groundwater <br /> monitoring and sampling activities <br /> 1 <br /> n 10540061reports1CL01195 doc 8 <br /> • <br /> 1 <br /> SMTH <br />