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1 Site Closure Summary <br /> Fuller Mobile Home Park August 8, 1997 <br /> 1 365 E. Louise Avenue, Lathrop, California Page. S <br /> i <br /> 1 <br /> 1 5.0 Soil & Groundwater Contamination <br /> This Site Investigation has identified an area approximately 100' in diameter around <br /> 1 monitoring well MW-3, installed at the former tank location This actual extent of soil <br /> contaminated above the water table is from -8 foot below grade level (bgl) to -11 foot bgl <br /> (Figure 7) The estimated secondary source volume of contaminated soils remaining in <br /> iplace is approximately 1,308 cubic yards, contamination levels from data collected in <br /> 1992-93 were used to calculate a mass balance of the soil contamination utilizing the <br />' worst case bases of impact The mas balance calculation estimates a total of 1,178 gallons <br /> of petroleum hydrocarbons in the soil at the time of the removal and a Groundwater Mass <br /> Balance Calculations estimates approxiamtely 15 gallon of petroleum in the groundwater <br />' mass (Appendix A) <br />' 6.0 Historical Groundwater Conditions & Gradient <br /> The groundwater gradient has varied from N 351 E to S 29° W over a 14 month period <br /> from April 1995 to May 1996 The flow rate has varied between 0036 ft /ft to 0074 <br /> ft/ft The groundwater gradient swings an estimated 200° plus over a period of a year <br /> due to tidal influence from the Delta and deep water channels in the area Those <br /> influences have the effect due to the relative flat slope of the gradient These conditions <br /> are not conducive to rapid migration of contaminates in the groundwater Historically <br />' groundwater has been recorded as high as -7, bgl and as low as -18' bgl (S SJID) <br /> (Appendix B) <br />' 7.0 Receptor Survey <br /> Y <br /> In February 6 1997 a completed Receptor Survey identified three (3) privately owned <br /> water wells and one (1) irrigation well within a 1,000 foot radius <br />' The irrigation well is located on the subject parcel in an up gradient location This well <br /> provides only landscape irrigation water All connections within the Mobile Home Park <br />' are to City of Lathrop Water Service The three (3) private water wells are due west of <br /> the subject parcel These parcels of property with wells are for sale and are zoned <br /> commercial All of the wells will be abandoned upon purchase by new owners and <br /> developed in commercial properties per the City of Lathrop Development Plan A single <br />