DWQ-2025-004557

Utah Division of Water Quality
Statement of BasisADDENDUM
Wasteload Analysis and Antidegradation Level I Review Date:May 7, 2025Prepared by:Christopher L. Shope Standards and Technical ServicesFacility:Emery County Coal Resources, Inc - Lilla
Canyon MineUPDES Permit No. UT-0026018
This addendum summarizes the wasteload analysis that was performed to determine water quality based effluent limits (WQBEL) for this discharge. Wasteload analyses are performed to determine
point source effluent limitations necessary to maintain designated beneficial uses by evaluating projected effects ofdischarge concentrations on in-stream water quality. The wasteload
analysis also takes into account downstream designated uses (UAC R317-2-8). Projected concentrations are compared to numeric water quality standards to determine acceptability. The numeric
criteria in this wasteload analysis may be modified by narrative criteria and other conditions determined by staff ofthe Division ofWater Quality.DischargeThere are three effluent discharge
points listed in the permit renewal application. Outfall 001: Sanitary package plant discharge; 1.0 MGDOutfall 002: Mine water discharge; 3.0 MGDOutfall 003: Sediment pond discharge;
1.0 MGDReceiving WaterThe effluent from Outfalls 001 through 003 will discharge into Lila Canyon Wash, which discharges to Grassy Wash, which flows into Marsh Flats Wash, discharging
to Price River, and into the Green River.Per UAC R317-2-13.1(b) the designated beneficial uses for:Price River and tributaries from confluence with Green River to confluence with Soldier
Creek, are:2B,3C,4.
Class 2B - Protected for infrequent primary contact recreation. Also protected for secondary contact recreation where there is a low likelihood of ingestion of water or a low degree
of bodily contact with the water. Examples include, but are not limited to, wading, hunting, and fishing.Class 3C - Protected for nongame fish and other aquatic life, including the necessary
aquatic organisms in their food chain.Class 4 - Protected for agricultural uses including irrigation of crops and stock watering.
Critical Low Flow
Typically, the critical flow for the receiving water in a wasteload analysis is considered the lowest stream flow for seven consecutive days with a ten-year return frequency (7Q10).
Lila Canyon Wash is an ephemeral dry wash, which only has flow during rain events. Therefore, there is no flow during critical conditions. No mixing zones are allowed for any of these
three effluent discharges and water quality concentrations must meet the numeric criteria at the end-of-pipe (EOP).Total Maximum Daily Load (TMDL)According to the Utah’s Final 2024 Integrated
Report on Water Quality dated April 30, 2024 (UDWQ, 2024), the receiving water for Outfall 001 discharge, Willard Canal was not assessed. The receiving water for Outfalls 001through
003effluent discharge“Price River and tributaries from confluence with Green River to confluence with Soldier Creek, (AU name: Price River-4, AU ID: UT14060007-014_00)”, are listed as
“Fully Supporting”. The Price River and tributaries from confluence with Green River to confluence with Soldier Creek has a site-specific standard for TDS of 3,000 mg/l.Mixing ZonePer
UAC R317-2-5, the maximum allowable mixing zone is 15 minutes of travel time for acute conditions, not to exceed 50% of stream width, and 2,500 feet for chronic conditions. Water quality
standards must be met at the end of the regulatory mixing zone. Lila Canyon Wash is an ephemeral dry wash, which only has flow during rain events. Therefore, there is no flow during
critical conditions. No mixing zones are allowed for any of the effluent dischargesand water quality concentrations must meet the numeric criteria at the end-of-pipe (EOP).Parameters
of ConcernThe potential parameters of concern (POCs) identified for the discharge/receiving water were determined in consultation with the UPDES Permit Writer, the Utah Water Quality
Assessment Reports, and the industry SIC codes from https://www.osha.gov/data/sic-search. The potential POCs for all three Outfalls from this facility include: total suspended solids
(TSS), total dissolved solids (TDS), dissolved oxygen (DO), and pH, while additional POCs for Outfall 001 include: biochemical oxygen demand (BOD5), total ammonia as nitrogen (TAN) and
E. coli. WET LimitsThe percent of effluent in the receiving water in a fully mixed condition, and acute and chronic dilution in a not fully mixed condition are calculated in the WLA
in order to generate WET limits. The LC50 (lethal concentration, 50%) percent effluent for acute toxicity and the IC25 (inhibition concentration, 25%) percent effluent for chronic toxicity,
as determined by the WET test, needs to be below the WET limits, as determined by the WLA. The WET limit for LC50 is typically 100% effluent and does not need to be determined by the
WLA. The WET limit for LC25 is also 100% effluent.Wasteload Allocation Methods
Effluent limits were determined for conservative constituents using a simple mass balance mixing analysis (UDWQ, 2021). The mass balance analysis is summarized in Appendix A. Several
of the dissolved metals standards and resulting total recoverable metals effluent limits are dependent on the hardness of the effluent. Because there was no hardness data submitted
in the permit application, the hardness of the mine water was conservatively estimated and was assumed to be 400 mg/L (as CaCO3).
The water quality standard for chronic ammonia toxicity is dependent on temperature and pH, and the water quality standard for acute ammonia toxicity is dependent on pH. The water quality
standards for ammonia are summarized in Appendices B and C. Fish early life stages were assumed absent in the receiving waters.
Since the receiving water is an ephemeral wash and not a perennial stream, the effects of TP, TN, DO and BOD5 in the effluent on the DO in the downstream receiving waters were not assessed.
It is presumed that secondary standards for BOD5 and water quality criteria for DO are sufficiently protective of the receiving water.Models and supporting documentation are available
for review upon request.Antidegradation Level I ReviewThe objective of the Level I 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. No evidence is known that the existing uses deviate from the designated beneficial uses for the receiving water. Therefore, the beneficial uses
will be protected if the discharge remains below the WQBELs presented in this wasteload.A Level II Antidegradation Review (ADR) is not required for this facility Per UAC R-317-2-3, because
the facility will maintain the same effluent discharge and water quality is not expected to be lowered by the proposed activity. Figure 1: Location map of outfalls, monitoring locations,
and surface water channels.
Documents:WLA Document:250507-Lila_Canyon_Mine_EOP_WLA_2025.docxWasteload Analysis and Addendums:250507-Lila_Canyon_Mine_EOP_WLA_2025.xlsxReferences:Utah Division of Water Quality.
2021. Utah Wasteload Analysis Procedures Version 2.0. https://documents.deq.utah.gov/water-quality/standards-technical-services/DWQ-2021-000684.pdfUtah Division of Water Quality. 2024.
Final 2024 Integrated Report on Water Quality. https://lf-public.deq.utah.gov/WebLink/DocView.aspx?id=87957&repo=Public&searchid=fcd9ea4c-51e1-4227-aa29-fb1921c2cc19&cr=1