SITE INFORMATION AND CORRESPONDENCE

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Antonia K. Vorster - 2 - 8 March 2011 r • During August and September 2003 UPRR initiated an emergency response consisting of using absorbent materials in Duck Creek to contain and remove the spilled fuel, plugging an affected drop inlet, and excavating about 315 cubic yards of diesel contaminated soil. • November 2003 to October 2004 — water pumped from the plugged drop inlet contained up to 110 mg/I TPHd. UPRR pumped and stored storm water in containers for treatment in the yard's onsite water treatment system. • February 2005 — storm-water grab samples from 12 culvert outflows (Fig. 4) away from the 2003 spill all contain TPH. Most culvert outflows contain TPHmo ranging from 0.3 mg/I to 10 mg/I at outfall SW-15. The drop inlet, which previously contained TPHd, now contains 3.5 mg/I TPHmo. • October 2005 — UPRR removed and replaced the drop inlet, culvert and about 140 cubic yards of soil. Of 18 confirmation samples, only one sample contained TPHd at 400 mg/kg, but 15 samples contained a "weathered TPH" in concentration ranging from less than 10 mg/kg to 40.mg/kg. • October 2005 — UPRR conducted an investigation of the storm water drainage system connecting to the sampled culvert outflows. The investigation collected 30 soil samples from 15 soil borings and attempted to map the drainage system using electromagnetic field induction. The study detected TPH ranging from 1.0 mg/kg to 500 mg/kg in each of the 26 soil samples analyzed. None of the sample chromatographs matched the diesel standard, but contained hydrocarbons in the C10 to C40 range. • 7 April 2006 — Regional Board staff letter noting that water in the replaced drop inlet continues to contain up to 1 mg/I of heavier fraction TPH. Staff concur that the TPH is not from the diesel spill and concur with removal of the culvert plug. Staff request further storm water monitoring from the culvert outfalls. • December 2006 storm water monitoring of seven culvert outfalls all contain TPH ranging from 0.3 mg/I to 1.5 mg/I, mostly of TPHmo range. The average sample contains about 1 mg/I of TPH. Extent defined: Pollution resulting from the 30 August 2003 diesel spill was defined and cleaned up. The extent of low level TPH contamination in the rail yard is unknown. Estimated Residual Petroleum Mass: Confirmation samples show minimal residual TPH from the original locomotive collision spill. However, an unknown amount of TPH from historical operations and Dustec application resides in the rail yard. Threat to Groundwater: Site remedial activities have eliminated the threat to groundwater quality from the locomotive spill. Widespread low-level residual TPH contamination in the yard results in storm run-off exceeding the taste and odor threshold of 0.1 mg/I for diesel. However, most of the TPH is heavier-end hydrocarbons that have no Water Quality Objective criteria. Threat to Human Health: • Vapor Intrusion Hazard: Confirmation sampling show primarily TPHmo and some TPHd. Based on this data there is no evidence of a vapor intrusion hazard at the site.