DSHW-2024-007742

August 14, 2024
Dean P. Anderson
Vice President
Tesoro Refining & Marketing Company, LLC
474 West 900 North
Salt Lake City, Utah 84103-1494
RE:ApprovalofMay 2024 Report of Current Conditions,
Marathon Refinery, Remote Tank Farm, and Truck Loading Rack,
Salt Lake City, UtahEPA #UTD000826362
Dear Mr. Anderson:
The Division of Waste Management and Radiation Control (Division) has completed it’s review of the May 2024 Report of Current Conditions (Report), for the Marathon Refinery (Refinery),
Remote Tank Farm (RTF), and Truck Loading Rack (TLR) collectively referred to and located in Salt Lake City, Utah (Site)that was prepared by the Antea Group (Antea)on August 5, 2024,forthe
Tesoro Refining and Marketing Company, LLC (Tesoro), a subsidiary of the Marathon Petroleum Company, LP (Marathon).
The Report summarizes the groundwater monitoring activities performed in May 2024 at the Refinery and the TLR including gauging of monitoring wells for light non-aqueous phase liquid
(LNAPL), collection of potentiometric data, and sampling of groundwater to evaluate the dissolved plume at the Refinery. The Report was performed in accordance and in compliance with
the Division approved Corrective Action Plan (CAP) which allowed for the discontinuation of groundwater monitoring at the RTF and the subsequent monitoring abandonment of RTF monitoring
wells.
Based on the results of the field efforts outlined in the Report, Contaminants of Potential Concern (COPCs) concentrations remain relatively consistent with historic sampling events
and the dissolved plume continues to be confined to the Refinery with no detections from monitoring wells at the TLR. Additionally, there was no detectable LNAPL in the one monitoring
well (01A) gauged at the TLR. The Report, however, indicates that monitoring well 02A was not accessible and therefore not gauged due to trenching activities at the TLR. No LNAPL has
been detected in 02A since a thickness of 0.08 feet was observed during the July 2023 gauging event. Detectable LNAPL thickness across the Refinery ranged from 0 to 0.07 feet during
the May 2024 gauging event.
When evaluating the potential impact to the downgradient residential community, the groundwater protection standard (GPS) of 0.00159 milligrams per liter (mg/L) derived from the vapor
intrusion screening level (VISL) for a potential off-site residential receptor was not exceeded in any off-Site sentinel wells.
The Division has no comments or questions concerning thisReport. The Report is hereby Approved.
If you have any questions, please call Ethan Upton at [phone].
Sincerely,
Douglas J. Hansen, Director
Division of Waste Management and Radiation Control
DJH/EAU/
c:Angela C. Dunn, MD, MPH, Health Officer, Salt Lake County Health Dept.
Dorothy Adams, Deputy Director, Salt Lake County Health Dept.
Ron Lund, Environmental Health Director, Salt Lake County Health Dept.
James Beardall, Marathon Petroleum Company, ([e-mail])
Chris Kaiser, Marathon Petroleum Company, ([e-mail])
Stuart J. Beling, Antea Group, ([e-mail])