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Home My WebLink AboutDWQ-2025-004839 195 North 1460 West • Salt Lake City, UT Mailing Address: P.O. Box 144870 • Salt Lake City, UT 84114-4870 Telephone (801) 536-4300 • Fax (801) 536-4301 • T.D.D. (801) 536-4284 www.deq.utah.gov Printed on 100% recycled paper State of Utah Department of Environmental Quality Kimberly D. Shelley Executive Director DIVISION OF WATER QUALITY John Mackey, PhD Director SPENCER J. COX Governor DEIDRE HENDERSON Lieutenant Governor M E M O R A N D U M TO: Dan Griffin, Permit Writer FROM: Suzan Tahir, Wasteload Analyst DATE: June 9, 2025 SUBJECT: Big West Oil Waste Load Allocation, Outfall 001 Receiving Water and Designated Uses (UAC R317-2-13): Outfall 001 discharges to an unnamed drainage ditch to the Salt Lake City Sewage Canal/Northwest Oil Drain (NWOD) and then into Farmington Bay of Great Salt Lake. In accordance with the Utah Administrative Code (UAC) R317-2-13, the unnamed drainage ditch and NWOD are classified as 2B and 3E and Farmington Bay, Great Salt Lake is classified as 5D. Class 2B Protected for infrequent primary and secondary contact recreation. Class 3E Severely habitat-limited waters. Narrative standards will be applied to protect these waters for aquatic wildlife. Class 5D Farmington Bay of the Great Salt Lake. Protected for infrequent primary and secondary contact recreation, waterfowl, shore birds and other water-oriented wildlife including their necessary food chain. Level I Antidegradation Review The objective of the Level I Antidegradation Review (ADR) is to ensure the protection of existing uses, defined as the beneficial uses attained in the receiving water on or after November 28, 1975. For this facility, the Level I ADR was conducted in accordance with the Interim Methods for Evaluating Use Support for Great Salt Lake Utah Pollution Discharge Elimination System (UPDES) Permits. A Level II ADR is based on the requirements of UAC R317-2-3. The proposed permit is a renewal with increase in flow or concentration over that which was approved in the existing permit. Page 2 Whole Effluent Toxicity (WET) Requirements The whole effluent toxicity (WET) requirements are based on the Utah Pollutant Discharge Elimination System Permit and Enforcement Guidance Document for Whole Effluent Toxicity (DWQ, February, 2018). As described in the Interim Methods, effluent pollutant concentrations are screened against Class 3D aquatic life numeric criteria to determine reasonable potential ensuring protection of the designated uses of the receiving waters. Only inorganic pollutants are considered because the source of the effluent is deep groundwater (>500’). Consistent with the other facilities discharging to NWOD, acute criteria are applied for the NWOD and acute and chronic criteria are applied at the downstream discharge to Farmington Bay. The approach was simplified to meeting the acute and chronic screening criteria in the NWOD because of the relatively low effluent flows (Table 1). The source of upstream flows in the NWOD are Warm Springs, the Salt Lake City Water Reclamation Facility (SLCWRF), the Chevron Refinery, and stormwaters. The data for flows in the NWOD are based on the Northwest Oil Drain and Salt Lake Sewage Canal Selenium, Ammonia and Flow Characterization Report (Stantec, May 10, 2018) (NWOD Report). The SLCWRF is the source of the majority of flow upstream of Big West Oil Outfall 001. Because the source of the most of the water is the SLCWRF effluent, ambient pollutant concentrations in the NWOD are based on concentrations measured in the SLCWRF effluent. These concentrations are reported in Table 1 of the January, 2014 Final Salt Lake City Water Reclamation Facility Effluent Screening Summary Report. The maximum allowable acute and chronic pollutant concentrations in the Big West Oil effluent are estimated using the minimum flow reported in the NWOD Report for the “Downstream of Chevron Outfall” monitoring location. The maximum concentrations for the SLCWRF effluent are derived from the long-term monitoring location (SALT LAKE CITY WWTP, 4991250) for the period 2014-2024. The Big West Oil allowable effluent concentrations for copper, chromium, and mercury concentrations are based on the chronic criteria because NWOD concentrations are at the criteria under the limiting conditions assumed. Tables 1, 2, and 3 summarize the assumptions and results. Table 1. Hardness and Flow NWOD Hardness mg/L CaCO3 NWOD Flow (MGD) Big West Oil Outfall 001 Acute (MGD) Big West Oil Outfall 001 Chronic (MGD) 400 35 0.55 0.33 Page 3 Table 2. Maximum Allowable Acute Effluent Concentrations for Big West Oil Outfall 001 Constituent Class 3D Acute Criteria (Dissolved) Maximum Concentration in NWOD (Dissolved) Maximum Allowable Concentration Outfall 001 (Dissolved) Maximum Allowable Concentration Outfall 001 (Total) Aluminum 0.7500 0.07 NA 43.27 Arsenic 0.3400 0.0115 99.12 99.12 Cadmium 0.0064 0.000184 1.88 2.12 Chromium VI 0.0160 0.00501 3.32 3.32 Copper 0.0496 0.0118 11.41 11.89 Lead 0.281 0.0016 84.26 143.05 Nickel 1.513 0.012 452.85 453.76 Selenium 0.018 0.0035 4.38 4.38 Zinc 0.379 0.103 83.37 85.24 Notes: All units mg/l 400 mg/L CaCO3 NA=not available NWOD = Northwest Oil Drain/Salt Lake Sewage Canal Table 3 Maximum Allowable Chronic Concentrations for Big West Oil Outfall 001 Constituent Class 3D Chronic Criteria (Dissolved) Maximum Concentration in NWOD (Dissolved) Maximum Allowable Concentration Outfall 001 (Dissolved) Maximum Allowable Concentration Outfall 001 (Total) Aluminum 0.87 0.07 84.848 84.848 Arsenic 0.15 0.0115 14.689 14.689 Cadmium 0.002 0.000184 0.193 0.226 Chromium VI/III 0.011 0.00501 0.011 0.011 Copper 0.029 0.0118 0.029 0.030 Lead 0.011 0.0016 0.997 1.693 Nickel 0.168 0.012 16.545 16.595 Selenium 0.0046 0.0035 0.117 0.117 Zinc 0.382 0.103 29.591 30.011 Iron 1 0.184 1 1 Mercury 0.000012 0.0046 0.000012 0.000012 Notes: All units mg/l 400 mg/L CaCO3 NA=not available; for aluminum, only acute criterion is applicable NWOD = Northwest Oil Drain/Salt Lake Sewage Canal Page 4 Whole Effluent Toxicity (WET) Biomonitoring WET biomonitoring requirements are based on the 2018 Utah Pollutant Discharge Elimination System Permit and Enforcement Guidance Document for Whole Effluent Toxicity. The immediate receiving waters are Class 3E, severely habitat limited and dilution of the effluent in the NWOD (also Class 3E) exceeds 20:1 and effluent flows are less than 20 MGD. Under these conditions, no specific modifications for Great Salt Lake are needed. Quarterly acute WET monitoring using alternating species of Ceriodaphnia dubia and Pimephales promelas (fathead minnow) and the standard permit language from Appendix A of the Utah WET guidance are recommended.