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z Y Page 10 July 12, 1991 Job No. 400511-E1 { contamination in the unsaturated zone. The estimated radius of influence for each of the proposed vapor wells, shown on Figure G, is based on field testing of existing wells at this site. Existing outlying wells(MW4,5,G,7,8,9, 10, 11, 16, 18, RW-24 and 26) may be used as air induction or air injection wells. Since some of these wells are currently manifolded in the equipment area, a conversion to an air induction or air injection well would be possible. MW4,5,and G will be piped to the equipment area in order to be used as air inlet wells. Air injection will enhance the volatilization of hydrocarbons in the vadose zone and will increase the vapor pressure gradient towards the vapor extraction wells. Air induction may be used initially, but as soil vent gas concentrations decline, air icilitate a greater degree of remediation in a shorter injection should be implemented in order to f period of time. 5.0 SCHEDULE implementation of the proposed monitoringwell and vapor extraction well installation will be contingent ' upon approval of this workplan,drill rig availability,permitting,and agency approval. DERS estimates that field work can be completed in ten days;laboratory results may take 2 to 4 weeks. An interpretive :a wells will be submitted to Conoco Inc.approximately six weeks report detailing the installation of t following the field work. Table A presents the estimated project schedule for installing the wells and preparing an interpretive report. i � 6.0 PERSONNEL AND PROCEDURES Subsurface exploration of the site will be performed by a DERS field geologist working under the supervision of a DERS California Registered Geologist. The field geologist will monitor the drilling program, log the boreholes, supervise the well installations, collect the soil samples, and coordinate delivery of the samples to a California-certified laboratory. DERS geologists and engineers will prepare a technical report based on exploratory findings. The licensed geologist will review the exploratory program, review the data, and participate in report preparation. Other employees of DERS, such as f: hydrogeologists,engineers,geologists, and technicians may provide services as needed. The investigation procedures (drilling and sampling protocol, chain-of-custody, etc.) will follow the guidelines from the LUFT manual (Central Valley Regional Water Quality Control Board) as demonstrated on other Conoco Inc.sites and described in the following sections: . ........... ... DU PONT ENVIRONMENTAL REMEDIATION SERVICES