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E C ® R <br /> Lli <br /> Cleanup Plan <br /> October 27, 2003 <br /> Page 10 <br /> ■ The proposed groundwater oxygenation system should increase dissolved oxygen <br /> concentrations in the saturated zone and thus enhance the biodegradation of on-site and off- <br /> site hydrocarbons. Oxygen-enriched groundwater should provide the environment for off- <br /> site hydrocarbons to degrade to levels near or consistent with the Basin Plan's WQOs. <br /> 5.0 TREATMENT SYSTEM DESIGN AND IMPLEMENTATION <br /> ' Treatment system design and implementation details are presented below. <br /> 5.1 Separate Phase Hydrocarbon Removal <br /> Groundwater will be extracted twice annually from any monitoring wells in which SPH is present, <br /> using a vacuum truck. Approximately 8,000 gallons can be extracted and stored by a vacuum truck. <br /> Therefore 8,000 gallons of groundwater can be extracted from monitoring wells where SPH is <br /> ' present during each event. <br /> 5.2 Limited Excavation <br /> Soil impacted with petroleum hydrocarbons near the former Keylock area (Figure 7) will be <br /> excavated to approximately 5 feet bgs or first encountered groundwater. Excavation will be limited to <br /> approximately 1,000 cubic yards and/or as facilities conditions permit. <br /> 5.2.1 Pre-Construction <br /> ' The construction bid package will be distributed to a minimum of three qualified contractors with <br /> experience performing similar projects. A bid walk will be performed to allow potential contractors to <br /> view the site and direct questions to the design engineer regarding construction specifications. <br /> ' Competitive bids will be procured and a contractor will be selected based on the contractors' <br /> capabilities to perform the work and bid price. The general construction specifications will present <br /> contractual language regarding the procedures and policies which guide the contractors work, <br /> ' including bonding, health and safety, and insurance requirements. <br /> 5.2.2 Construction <br /> SECOR will perform construction management services during excavation activities. These services <br /> include on-site management of contractor, subcontractors, and other SECOR personnel. <br /> Vapor headspace monitoring will be conducted on soil samples to determine the limits of excavation. <br /> Confirmation soil samples will be collected from the limits of excavated areas submitted to a <br /> California state certified laboratory, and analyzed for the following constituents: <br /> ' • TPHg and TPHd using modified EPA Method 8015, <br /> • Benzene, toluene, ethylbenzene, and xylenes (BTEX) by EPA Method 8260B, <br /> • MtBE, tertiary amyl methyl ether (TAME), tertiary butyl alcohol (TBA), 1,2-dichloroethane <br /> ' (1,2-DCA), 1,2 dibromoethane (EDB), di-isopropyl ether (DIPE) and ethyl tertiary butyl ether <br /> (EtBE) by EPA Method 8260B, and, <br /> • Total lead by EPA Method 60108. <br /> ' I:\Chevron\1001621\REPORTS\2003\2003-Cleanup Plan\Cleanup Plan.doc <br />