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1 <br /> Report-Pilot Remedial System Test Page 2 <br />' Former Manna Pro Site <br /> Project No 207 3 <br /> July 31, 2000 <br />' high levels of gasoline and aromatic hydrocarbons (especially benzene) in groundwater <br /> samples collected from on-site wells, however, suggest that natural attenuation is not <br /> adequately mitigating the groundwater plume Manna Pro therefore agreed to investigate <br /> several potential methods of engineered remedial action which may be employed to <br /> adequately mitigate the contaminated groundwater A Work Plan was submitted which <br /> r proposed methods and protocols to conduct work to investigate the feasibility of several <br /> options designed to remove petroleum hydrocarbons from the subsurface This work was <br /> intended to enhance and supplement previous pilot work documented in the report <br /> rentitled Pilot Testing Report and Conceptual Corrective Action Plan, dated July 15, <br /> 1994, by Groundwater Technology Inc (GTI) The Work Plan also proposed that a deep <br /> monitoring well be constructed to characterize the vertical distribution of petroleum <br /> rhydrocarbons in deeper groundwater aquifers The construction, sampling and analytical <br /> results of the deep monitoring well are documented separately in a June 2, 2000 report <br /> entitled Report, Sprang 2000, Quarterly Groundwater Monitoring and Dee.Monitoring <br /> Well Construction This current report documents the work completed in the remedial <br /> pilot test program A third report, a Remedial Action Feasibility Study, will be <br /> r forthcoming which will discuss several potential remedial action alternatives and their <br /> prospects to effectively and efficiently mitigate the contamination in the subsurface <br /> r• 1.1 Site History <br /> The former Manna Pro facility was originally constructed in 1956 as a grain mill which <br /> r processed animal feed products Two 10,000 gallon underground diesel tanks and two <br /> 5,000 gallon underground gasoline tanks and a single 10,000 gallon underground gasoline <br /> tank were formerly in use at the site These tanks were used to fuel vehicles operated at <br /> r the facility The former tanks were located Just northeast of the main entrance to the <br /> Property from El Dorado Street <br /> r In January 1990, as part of an environmental site assessment, Manna Pro's Consultant at <br /> that time, WHF, installed six soil borings near the tanks and soil samples were collected <br /> from the borings One soil sample, collected from 15 feet below grade, contained <br /> relevated levels of gasoline and diesel range hydrocarbons In July of 1990, Semco, a tank <br /> removal contractor, removed the tanks under contract to WHF and a total of 10 <br /> r confirmation soil samples were collected beneath the tanks, one from each end of each <br /> tank Petroleum hydrocarbons were detected in soil samples from beneath 4 of the 5 <br /> tanks Based on the results of this initial soil sample analysis, several hundred yards of <br /> rfuel impacted soil were excavated The excavation reached a total depth of about 15 feet <br /> In October of 1990, ERM West conducted additional work to characterize the lateral and <br /> vertical extent of the hydrocarbon contamination in the sub-surface This included <br /> installing 25 soil borings into groundwater of which, a total of 6 borings were later <br /> r2937 Veneman Ave, 413240 Geo-Phase Environmental Inc Phone(209)569-0293 <br /> Modesto, CA 95356 Fax(209)569-0295 <br /> r <br />