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f G1eokykafTahnics Inc. Page 2 Moresco(Gawne Rd.) Addendum to 418197 Work Plan Project No.21.3 ' April 21, 1997 2.0 Design of Extraction and Passive Recharge Wells Past experience has shown that screen lengths of 20 feet maximizes extraction efficiency in this type of sediment. The distances between extraction and recharge points of 20 to 30 feet are effective for this site because that is the area that has the elevated concentrations of gasoline. 3.0 Radial Influence Testing As documented in the work plan of April 8, 1997 a radial influence test will be conducted once the subsurface has equilibrated and the vapor extraction system is running at peak performance. Once the optimum setup of the air recharge wells is determined the system will be run in this configuration with configuration adjustments made periodically to help prevent channeling from developing. 4.0 Monitoring Equipment Unless otherwise noted all monitoring equipment will be portable in order to reduce duplicate equipment purchases and the possibility of vandalism or theft. Flow Meters- To measure airspeed, and hence calculate extraction volumes, a Solomat MPM- 500e with a pitot tube will be used. Air speed measurements will be taken through a port in a six foot straight length of PVC piping between the extraction well and the T.O. unit. Early in the system startup it will be necessary to draw atmospheric air through a bypass valve. A port will be set in a six foot section of straight FVC pipe to allow for measurement of airspeed going through the bypass. Direct measurement of airspeed in the exhaust stack is not possible due to high temperatures but if influent volumes, both extraction and bypass, are known then influent is also known as influent=effluent. This has proven acceptable to the S3VUAPCD. Vacuum Gauges-In order to determine vacuum influence at the recharge wells either Magnehelic gauges or the MPM-500e will be used. These will be attached to the recharge wells by hose barbs fitted to slip-on PVC caps. A permanent vacuum gauge .is attached to the TO unit upstream of the blower which shows vacuum in inches of mercury being pulled by the system. Temperature Sensors- Temperature is measured in the combustion chamber and displayed by a Honeywell UDC 2000 Mini-Pro. The Mini-Pro also has a temperature limit feature on it. If combustion temperature drops below 1450°F or goes above 1650°F it shuts the system down automatically. A Rustrak Model Z-55 chart recorder provides a continuous record of combustion temperature. The Mini-Pro and Rustrak are both permanent pieces of equipment. To measure influent air temperatures the MPM-500e will be used with a thermocouple. Temperature measurements will be taken through the same port that is used for airspeed measurements. Sampling: • Sampling Ports - One sampling port will be a hose barb set into the PVC piping between the Extraction well and the TO unit. A second sampling port will be a hose barb that is set into the piping downstream of the bypass valve. We have found this location to give more reliable samples. Due to high temperatures of the effluent stream we use a five foot length of copper tubing to pull the effluent samples through. This method is approved by the S.IVUAPCD.