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ROYAL OAK SAVINGS & LOAN Insitu-Treatment Soil Gas Extraction Air Quality Permit Application Page 3 2 0 PROPOSAL This project has been designed to remediate a contaminated soils condition at the current shopping plaza, located at the northeast corner of Alameda and North Main Street in Manteca, California (Figure 1) Under the direction of WHF with the approval from San Joaquin County Environ- mental Health and the Air Pollution Control District, a soil vapor extraction system will be installed to remediate the subsurface contamination left in place from the excavation, located at the southern edge of the site (near MW-2) The contaminated soils were left in place because their removal would have caused the remedial excavation side wall to fail, endangering the workers and civil structures (sidewalk, street pavement, buried utilities) ' WHF proposes to install a vacuum pump over MW-2 The piping will extend 15 feet to the north of MW-2 into two (2) carbon drums (in series) The vapor extraction systern will be caged An air test was conducted prior to see if the system would work efficiently The system will be periodically tested If the air and water samples test "none detected" after three to four (3-4) months (maximum of six months), WHF will submit a report recommending site closure r 3.0 CHEMICAL COMPOSITION OF CONTAMINANTS The average Xylene content of these soils is estimated to be 550 ppb (EPA proposed MCL = 1,750, DOHS action level = 650 , based on samples from borings B-1 and B- 2 At this concentration level, the 20 7 yards3 of contaminated soil would contain approximately 16 24 grams (0 568 ounces) of Total Xylene 4.0 CONTAMINATED SOIL DATA The quantity of contaminated soil left in place in the south edge of the remedial excavation, at this site, is projected at approximately 20 7 yards3 The contaminated soils are at a depth of 22 feet, they could occupy an area of 560 feet and have a thickness of one foot (1')