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2020 Steam Electric Reconsideration Rule – Effluent Limit Guidelines (ELG) Update


On August 31, 2020, the EPA finalized revisions to the effluent limit guidelines (ELG) for the steam electric power generating category (40 CFR Part 423). This pre-publication version of the ELG is named the 2020 Steam Electric Reconsideration Rule. The rule revises requirements for two specific waste streams produced by steam electric power plants: flue gas desulfurization (FGD) wastewater and bottom ash (BA) transport water. The latest guidelines contain much of the same content as the previous rule but includes additional reporting requirements for plants. The new update also changes the technology-basis for treatment of the waste streams, revises the voluntary incentives program for FGD wastewater, adds subcategories for generating units, adjusts discharge limits, and establishes new compliance dates. Finally, the latest rule shifts the focus from meeting federal guidelines to working with state authorities.

Updated Effluent Limits

The date to meet the updated regulations for FGD and BA transport water is one year after the rule is published in the Federal Register. The final rule is expected to be published this fall but will be implemented no later than December 31, 2025. Note that all generating plants must comply with applicable CCR deadlines regardless if FGD and/or BA transport water requirements have been implemented.

The updated effluent limitations for FGD wastewater are:

The final rule establishes a voluntary incentive program (VIP) that allows more time for plants to meet new standards and limitations if they adopt additional process changes and controls that achieve more stringent limitations. This optional program was included in the previous rule as well. It offers environmental protections beyond those achieved by the final BAT limitations, while providing plants that opt into the program more flexibility and additional time to meet the limitations in the final rule.  Plants are required to meet these regulations by December 31, 2028. Updated VIP effluent limits for FGD units are:

Bottom Ash Transport Water Limitations

In contrast to the concentration-based, numeric limitations estimated for specific pollutants above, EPA is finalizing a pollutant discharge allowance in the form of a site-specific percentage purge rate for BA transport water with a maximum cap. Bottom ash purge will have a maximum of 10% of system volume purged on a rolling 30-day average for each plant. However, the actual purge volume allowed, and any specific effluent limits will be established by state permitting authorities on a case-by-case basis. This change effectively shifts responsibility for setting compliance standards to the states rather than from federal guidelines.

Low Utilization Subcategory

The final rule establishes a subcategory for Low Utilization Electric Generating Units (LUEGUs) with a two-year average capacity utilization rate (CUR) of less than 10% per year. This subcategory applies to plants that operate well below full capacity on an annual basis. The CUR is calculated as the total MWh of production divided by the hours per year times the nameplate capacity. To qualify for low utilization status, plants must provide official notification of their intent to participate in this subcategory. These plants must also recertify annually based on a two-year average capacity utilization rate and develop a best practices management plan for each low-utilization boiler at the plant.

FGD wastewater generated by a unit under the low-utilization subcategory will need to meet the updated guidelines potentially as soon as one year after publication of the rule but in no case later than December 31, 2023. Effluent limits for low utilization FGD units are:

Other Requirements

The final rule includes other requirements that necessitate careful consideration when evaluating options for a path forward for generating units that are affected by the new/updated rules. For example, the final rule includes a myriad of new and revised reporting requirements. Plants must now document and track various operating parameters related to their bottom ash sluicing systems. They must document design information about their bottom ash systems and potential discharges from the system. System owners must provide a detailed narrative describing all water treatment systems available at the plant. Finally, the rule includes an exemption for plants that will close prior to 2028. This exemption was clarified to include plants that will cease operation on coal prior to 2028, such as units that convert to natural gas firing.

If you need help navigating the new 2020 effluent limit guidelines, we are here to help! Contact us for more information at You can view the complete ELG document on the EPA website:

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