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i ..._ 1 r-. EXECUTIVE SUMMARY This report describes the plan to remediate petroleum hydrocarbon impacted soil and groundwater at the former Manteca Bean Facility located in Manteca,California. The facility is owned by the Golden Grain Company of San Leandro, California. The source of petroleum hydrocarbons was leakage from a 700-gallon underground gasoline storage tank removed in November, 1986. A Problem " Assessment Report (PAR) for the Manteca Bean Farility was submitted to San Joaquin County Public Health Services and to the Regional Water Quality Control Board-Central Valley in December,1989. The N PAR defined the site geology and hydrogeology, and the distribution of petroleum hydrocarbons in the soil and groundwater. The boundaries of hydrocarbon impacted soil and groundwater were fully defined during the PAR investigation. The extent of subsurface hydrocarbons is relatively localized-,at distances greater than 110 feet from the former underground storage tank hydrocarbons are not detectable by standard laboratory methods. Curren€ly,the site does not pose an imminent threat to public health or the environment. Soil in the unsaturated zone will be remediated by a soil vapor extraction system, and groundwater will be remediated by a pump and treat system. Both systems will produce hydrocarbon- laden vapors that will be treated on-site utilizing a catalytic oxidation unit. The design goal is to remove petroleum hydrocarbons from the subsurface and achieve greater than 90%destruction of the extracted F. t materials on site prior to discharge. ailed consists of two 1.5 horsepower regenerative The soil vapor extraction system to be inst blowers attached to two existing monitoring wells. The applied vacuum induces subsurface air flow and volatilization of adsorbed hydrocarbons. The extracted vapors will be destroyed on site in the catalytic oxidation unit. Groundwater Technology has permitted and operated.�everal similar units in California. After the pumping well is permitted and installed,an aquifer test is required in order to finalize the design of the groundwater treatment system. The pump and tred:system to be installed consists of a pumping well arid air stripping tower. Groundwater is pumped from the subsurface and develops a^cone of depression'and in turn establishes hydraulic control over the plume of dissolved phase hydrocarbons. Groundwater 1..pw3sed through an air stripping tower to volatilize greater than 99%of the hydrocarbons from the groundwater. Treated water will either be discharged to the City of Manteca sewer system or recharged on site. Off-gas from the air stripper will be routed through the catalytic oxidation unit prior to discharge. Groundwater Technology will obtain all permits required to construct and operate the treatment system. All remediation equipment will be monitored on a regular basis for the life of the project to ensure optimal running conditions and to comply with permit standards. � GRut?Nmv,rriat 'I CC IINcll.UGl;IINc.