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' Report—Fist Phase Remedial System Page 2 Former Manna Pro Site ' Project No 1011 June 18, 2002 ' 1.1 Site History The former Manna Pro facility was originally constructed in 1956 as a grain mill that ' processed animal feed products Two 10,000 gallon underground diesel tanks and two 5,000 gallon underground gasoline tanks and a single 10,000 gallon underground gasoline ' tank were formerly in use at the site In January 1990, as part of an environmental site assessment, Manna Pro's consultant at that time, WHF, installed six soil borings near the tanks and soil samples were collected from the borings One soil sample, collected from ' 15 feet below grade, contained elevated levels of gasoline and diesel range hydrocarbons In July of 1990, Semco, a tank removal contractor, removed the tanks under contract to WHF and a total of 10 confirmation soil samples were collected beneath the tanks, one ' from each end of each tank Petroleum hydrocarbons were detected in soil samples from beneath 4 of the 5 tanks Based on the results of this initial soil sample analysis, several hundred yards of fuel-impacted soil were excavated The excavation reached a total ' depth of about 15 feet In October of 1990, ERM West conducted additional work to characterize the lateral and ' vertical extent of the hydrocarbon contamination in the sub-surface This included installing 25 soil borings into groundwater of which, a total of 6 borings were later • converted to groundwater monitoring wells Between 1993 and 1996, Groundwater Technology Inc (GTI) installed four additional monitoring wells, a combination groundwater/vapor extraction well and three observation wells These observation wells were used for the completion of groundwater pumping and vapor extraction pilot tests In 1996, GTI conducted a feasibility study, which included pilot level field work to test several remedial options The GTI report concluded that a combination of vapor ' extraction and groundwater pumping offered the most attractive option for remediation of the gasoline plume at this site ' Up until April of 2000, a total of eleven groundwater monitoring wells, three observation wells, and one combination groundwater and vapor extraction well were constructed on or near the Manna Pro site In April of 2000, Geo-Phase constructed a deep monitoring well to characterize the vertical extent of gasoline contamination, and also conducted a pilot field study to test and evaluate the effectiveness of a vapor extraction and air sparge system As a part of the pilot study, a new vapor extraction well (VEW-1), a new sparge ' well (ASW-1), and two new observation wells (OB-4 & OB-5) were constructed After evaluating the data from the pilot study, Geo-Phase Environmental completed a Feasibility Study on October 20, 2000 The study concluded that the most attractive option was to simultaneously inject air into sparge wells and to extract gasoline-laden vapors from the vadose zone using vapor extraction wells Subsequently, a Corrective Action Plan was prepared and submitted on February 16, 2001 that described the methods and protocols to be used to construct and operate the proposed remedial system The ' 2937 Veneman Ave, #B240 Geo-Phase Environmental Inc Phone(209)569-0293 Modesto,CA 95356 Fax(209) 569-0295