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Memo to Mr. Chris Flower - 2 - 29 July 2021 Joaquin County Environmental Health Department (SJCEHD) initially responded to the release. TREATMENT AREA The treatment area is a portion of CCT track where red dye, a tracer additive to diesel, was visually observed to have stained the soil. UPRR removed 80 feet of track, which extended outside of the impacted area to excavate impacted soils and ballast. UPRR excavated soil and ballast beyond the visually observed impacted area, with the total extent of excavation measuring 45 feet long, 18 feet wide, and 3 feet deep. ACTIONS On 22 July 2020, after the diesel release, Ground Penetrating Radar Systems, LLC conducted a utility locate and found no utilities. Arcadis located and inspected nearby sewer and storm drains. Diesel was not observed in the municipal utilities. On 22 July 2020, vacuum trucks and absorbent pads were used to capture free- phase diesel on the ground surface and between railroad ties. Absorbent pads were left overnight in potholes and trenches to collect additional diesel. Impacted ballast and soil were recovered and stockpiled for waste characterization. On 23 July 2020, 80 feet of track was removed and an area of 45 feet long, 18 feet wide was excavated to approximately 3 feet. A photoionized detector (P ID) was used to screen the soil for volatile organic compounds (VOCs) to determine the extent of excavation. On 23 July 2020, six confirmation samples were taken from the excavation floor and sidewalls. Upon approval of an SJCEHD representative, the excavated area was backfilled with imported crushed rock subbase and new imported ballast. UPRR characterized the approximately 118 tons of waste material to be non- hazardous and disposed of the waste between 21 August 2020 and 25 August 2020. Copies of the waste manifests have been provided to the Central Valley Water Board. RATIONALE UPRR and its contractors responded to the release by implementing recovery and control measures immediately and completed source area excavation with confirmation sampling the day after the release. A PID was used to screen for VOCs and ensure any diesel-impacted soil was removed. In addition, the highest detections of Total Petroleum Hydrocarbons as Diesel Range Organics (TPH-DRO) and Oil Range Organics (TPH-ORO) from the six confirmation samples were 9.19 milligrams per kilogram (mg/kg) and 42.6 mg/kg, respectively. The detections of these constituents of concern (COCs) are substantially below the residential shallow exposure Environmental Screening Levels (ESLs) of 260 mg/kg for TPH-DRO and 12,000 mg/kg for TPH-ORO. While the Site is used for commercial operations and is expected to remain as such,