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SITE CLOSURE REPORT <br /> General Mills, Inc <br /> 2000 West Turner Road <br /> Lodi, California <br /> Delta Project No D092-708 <br /> Page 7 <br /> operations and assumptions based on the soil characteristics and concentrations of hydrocarbons beneath <br />' the tanks <br /> Based on the size of the removed tanks (12,000 gallon), standard installation details indicate that the USTs <br /> should be placed 4 feet bsg with a 1 foot base of gravel Standard dimensions for a 12,000 gallon tank <br />' are 8 feet In diameter and 32 feet to length Using this construction and the diameter of the tank, the <br /> base of the tanks would have been 13 feet bsg This depth correlates with the sampling depth of 15 feet <br /> bsg To calculate the possible volume of hydrocarbons in soil beneath the tanks, Delta has assumed that <br /> there was a uniform lateral plume of hydrocarbons beneath the former tanks within the limits of the <br /> excavation (30 feet by 35 feet) Within this plume, an additional assumption is made based on the <br />' concentrations of hydrocarbons In soil reported in analytical results with respect to depth Utilizing the <br /> maximum concentrations reported in soil samples collected In the soil borings and during tank removal <br /> activities, Delta assumes that the average concentration of hydrocarbons in soil between 13 and 14 5 feet <br /> bsg was 10,000 ppm, between 14 5 and 16 feet bsg the average concentration was 1,000 ppm, and <br />' between 16 and 18 feet bsg the average concentration was 100 ppm Hydrocarbons were not reported <br /> above the laboratory's limits of detection below 17 5 feet bsg in any soil boring <br /> silt with <br /> Soil types logged beneath the former tanks indicate that the soil ranges from a poorly ggraded s <br />' sand to a silty sand An average porosity for these types of soils is approximately 40 percent (Freeze and <br /> Cherry, 1979) Based on a worst case, Delta assumed that the entire pore volume of the soil was <br /> saturated with fuel oil <br />' Utilizing the assumed lateral and vertical limits, porosity, and hydrocarbon concentrations with depth, <br /> an initial volume of less than 53 gallons of fuel oil, quantified as diesel No 6 may have been present In <br />' soil beneath the former tanks prior to excavation Calculation of the volume of hydrocarbons are <br /> presented to Appendix B <br /> RPT137 SIS <br />