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i <br /> i <br /> 1 <br /> A.Telchent&Son Inc.Mobile Equipment Shop 143 N.V St.Stockton,CA. <br /> Remedial Action Alan March,1994 <br /> 442 Monitoring Recommendations <br /> Subsequent to securing required permits and system installation, we recommend the <br /> following: <br /> 1. Collection of groundwater samples from newly constructed well MW-14 prior <br /> to SVE operation. This baseline data should be collected before the <br /> operational system affects groundwater conditions. <br /> 2. A groundwater "grab sample" should be collected from MW-9. This well is <br /> obstructed above the water table and has not been sampled since ,June 10, <br /> 1991. The sample may provide upgradient groundwater data. <br /> 3. The well heads to existing wells MW--4 and MW-5 should be replaced, and <br /> the well vacuums monitored during initial system operation. The monitoring <br /> 1 may verify the radius of influence in these areas. <br /> Subsequent to initial system operation, we recommend the following: <br /> 1. Careful evaluation of effluent chemical sample analysis. Based upon current <br /> r! TPH gas BTEX analysis and system design, the system is expected to <br /> generate up to 5 lbs/day of benzene prior to treatment. Subsequent to 99% <br /> destruction efficiency, this amount would be reduced to 0.05 lbs/day. If for <br /> any reason benzene destruction efficiency falls much below design criteria, <br /> excessive quantities of benzene may be released. We strongly recommend <br /> air plume modeling/risk assessment if benzene release from the system <br /> exceeds 0.15 lbs/day. The modeling should identify potential receptors, <br /> potential inversion areas, air flow patterns, and document cancer risk from <br /> the system effluent within 1,000 feet of the site. <br /> 2. The continuation of existing quarterly groundwater sampling and reporting. <br /> If the grab sample from MW-9 indicates detectable concentrations of <br /> gasoline constituents, MW-9 should be included in the monitoring. Because <br /> the screen of MW-13 is below the water table, we recommend that MWA 4 <br /> supplant MW-13 for routine quarterly groundwater monitoirng. The <br /> groundwater analysis may be utilized to determine the effectiveness of SVE <br /> 1 on impacted groundwater. <br /> 1 <br /> 9 ' <br /> 1 <br />