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Four K Farms - 2 - 25 July 2019 the summer to allow for aeration. The stockpiled soil was also turned cccasionally to promote biodegradation. Remedial activities and confirmation sampling indicate that diesel -contaminated soil has been removed to the extent practicable and there are no remaining significant threats to public health or the environment. Stockpile sampling results indicate that the stockpile has been adequately treated to be reused as road base at the Site. Setting: The land surrounding the Site is primarily agricultural with associated private residences. A nut processing facility is located to the west of the Site. Two domestic wells are located onsite. Depth to groundwater was reported to be approximately 22 feet below ground surface (bgs). Source: The source of the diesel release was a catastrophic failure of the AST during filling operations. The AST contained approximately 6,000 gallons of diesel at the time of the tank failure. Actions: For logistical purposes, the spill was separated into three area:;: the front orchard area, the driveway area, and the rear orchard area. The front orchard area, located furthest from the diesel AST, was excavated to a depth of approximately 6 to 10 feet bgs and measured approximately 80 feet long by 22 feet wide. Total petroleum hydrocarbons as diesel (TPH-d) analytical results for the initial soil samples collected from the front orchard area at a depth of 4 feet bgs were less than 100 milligrams per kilogram (mg/kg) with the exception of one sample, SW -5@4'. The area of SW -5@4' w;is over -excavated to 6 feet bgs, until no visual or PID indications of diesel impact were noted. The driveway excavation area was excavated to a depth of approxima :ely 4.5 to 9 feet bgs and measured approximately 275 feet long by an average width of approximately 6 feet wide. The west end of the excavation expanded to a width of 25 feet. TPH-d analytical results for confirmation samples from the base of the excavation were all less than 1 mg/kg. The rear orchard area, located nearest the diesel AST, was excavated to a depth of approximately 6 to 12 feet bgs, with the majority of the excavation extending to 12 feet bgs where a "cemented clay/silt hardpan" was encountered. The excavation was irregularly shaped, measuring approximately 150 long and varying in mfidth from approximately 15 feet at the ends to approximately 60 feet near the middle. Except for two confirmation soil samples TPH-d concentrations were less than 100 mg/kg, ranging from non -detect to 57 mg/kg. The two confirmation soil samples that exceeded 100 mg/kg were OS -B@11' and OS -G@12.5' with concentrations of 240 rrg/kg and 252 mg/kg, respectively. These concentrations are below the Region 2 Regional Water Quality Control Board Tier 1 Environmental Screening Level (ESL) for diesel of 260 mg/kg. Subsequent to completion of excavation and confirmation soil sampling activities, the excavations were backfilled with clean fill dirt. On 11 May 2015, groundwater samples were collected from the two onsite domestic wells and analyzed for TPH-d. Depth to groundwater was reported to be approximately 22 feet bgs. TPH-d was not detected in either groundwater sample.