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`rel , Soil Vapor Extraction and Air Sparging Performance Monitoring Plan Stockton Yard Maintenance Facility,Stockton Page 2-3 measurements. If OVM concentrations influent to the SUETS appear low, then the system should be evaluated for leaks,vacuum adjustment,well concentrations, or dilution air quantities. It is recommended that OVM concentrations from individual wells be evaluated on a monthly basis prior to sample collection for laboratory analysis. Sampling ports are provided at the vapor extraction well manifold in order to collect vapor well samples. If individual vapor well OVM concentrations are less than approximately 50 parts per million (ppm),the well valve should be closed to prevent reduction/dilution to influent oxidizer concentrations. However, SVETS optimization performed by closing well valves should also take into account reduction in air flow rates to the oxidizer as the unit will shut down if the influent air flow is too low,below 20 cfm (566 L/min). The SUETS and AS radius of influence can be checked at the site by measuring the vacuum or pressure at individual wells. A vacuum/pressure gage can be connected to each wells' sample port or other site monitoring wells (utilizing a well cap with installed fittings)while the SVETS and AS are operating in order to measure SVETS vacuum influence and AS pressure influence. The site radius of influence will be modified as a result of AS operation. Air samples for laboratory analysis must be collected monthly in accordance with air quality permit conditions. These samples are to be analyzed by a California-certified analytical laboratory using EPA Method TO-3 for TPH-G and BTEX. Influent samples are collected in a 1.0-liter Tedlar bag by placing the Tedlar bag inlet into the sample port located on the pressure side of the vacuum blower. Effluent SVETS samples are collected using a 1.0-liter Tedlar bag,vacuum box,and a small pump connected to the vacuum box outlet. Samples collected for laboratory analysis must be stored at ambient temperature in a closed box or dry cooler to prevent exposure to sunlight during transport and storage. The hold time for air samples collected in Tedlar bags is 72 hours from the time of collection to the time of analysis. Longer holding times can be attained if laboratory-certified Summa canisters are utilized. Air flow measurements must be collected monthly at the oxidizer inlet and outlet when laboratory bag samples are obtained. An air flow meter is installed on the SUETS;however,in the event of a meter failure,a "standard"type, stainless steel pitot tube can be utilized to measure inlet differential pressure. An"S" type stainless steel pitot tube is required to measure the oxidizer outlet differential pressure because of stack access limitations. The pitot tubes can be connected to either Magnehehc or Manometer differential pressure gages. This data is used to determine air velocity and calculated air flow rates based on pitot tube manufacturer's equations. Note that the MMC-5A oxidizer inlet and outlet flow rates are identical since no air is added in the oxidizer combustion chamber. The permitted air flow rate through the SVETS is 100 scfm (2,832 L/min). Actual soil vapor extraction flow rates will vary based on site soil conditions,water entrainment, and the quantity of dilution air. Little maintenance is required for the vacuum blower. Replacement of the inlet particulate air filter element is required periodically. The vacuum blower was constructed with sealed bearings which require no maintenance. The blower hours of operation can be determined from the totalizing hour meter located on the oxidizer control panel. D:\PNIIP\Stockton Yard PMP.doc