| Commitments and Contingencies | Commitments and Contingencies Overview There are various claims and lawsuits pending against the Company. In addition, the Company is subject to federal, state, and local environmental laws and regulations and periodically participates in the investigation and remediation of various sites. In addition, the Company periodically enters into financial commitments in connection with its business operations. Also, the Company is involved in various legal and regulatory proceedings in the normal course of its business. See Note 12. It is not possible at this time for the Company to determine fully the effect of all litigation and other legal and regulatory proceedings on its financial position, results of operations, or cash flows. With respect to some of the items listed below, the Company has determined that a loss is not probable or that, to the extent probable, cannot be reasonably estimated. In some cases, the Company is not able to predict with any degree of certainty the range of possible loss that could be incurred. The Company assesses legal and regulatory matters based on current information and makes judgments concerning their potential outcome, giving due consideration to the nature of the claim, the amount and nature of any damages sought, and the probability of success. Such judgments are made with the understanding that the outcome of any litigation, investigation, or other legal proceeding is inherently uncertain. In accordance with GAAP, the Company records liabilities for matters where it is probable a loss has been incurred and the amount of loss is reasonably estimable. The actual outcomes of the items listed below could ultimately differ from the judgments made and the differences could be material. The Company cannot make any assurances that the amount of reserves or potential insurance coverage will be sufficient to cover the cash obligations that might be incurred as a result of litigation or regulatory proceedings. Except as otherwise disclosed, the Company does not expect that any known lawsuits, environmental costs, and commitments will have a material effect on its financial condition, results of operations, or cash flows. Additional information concerning commitments and contingencies is contained in Note 16 of the Notes to Consolidated Financial Statements in the 2019 Annual Reports on Form 10-K. Commitments and Contingencies Related to the Environment Nuclear Spent Fuel and Waste Disposal Nuclear power plant operators are required to enter into spent fuel disposal contracts with the DOE that require the DOE to accept and dispose of all spent nuclear fuel and other high-level radioactive wastes generated by domestic power reactors. Although the Nuclear Waste Policy Act required the DOE to develop a permanent repository for the storage and disposal of spent nuclear fuel by 1998, the DOE announced that it would not be able to open the repository by 1998 and sought to excuse its performance of these requirements. In November 1997, the DC Circuit issued a decision preventing the DOE from excusing its own delay but refused to order the DOE to begin accepting spent nuclear fuel. Based on this decision and the DOE’s delay, a number of utilities, including APS (on behalf of itself and the other PVNGS owners, including PNM), filed damages actions against the DOE in the Court of Federal Claims. The lawsuits filed by APS alleged that damages were incurred due to DOE’s continuing failure to remove spent nuclear fuel and high-level waste from PVNGS. In August 2014, APS and the DOE entered into a settlement agreement that establishes a process for the payment of claims for costs incurred through December 31, 2019. In July 2020, APS accepted the DOE's extension of the settlement agreement for recovery of costs incurred through December 31, 2022. Under the settlement agreement, APS must submit claims annually for payment of allowable costs. PNM records estimated claims on a quarterly basis. The benefit from the claims is passed through to customers under the FPPAC to the extent applicable to NMPRC regulated operations. PNM estimates that it will incur approximately $59.6 million (in 2019 dollars) for its share of the costs related to the on-site interim storage of spent nuclear fuel at PVNGS during the term of the operating licenses. PNM accrues these costs as a component of fuel expense as the nuclear fuel is consumed. At September 30, 2020 and December 31, 2019, PNM had a liability for interim storage costs of $13.1 million and $12.7 million, which is included in other deferred credits. PVNGS has sufficient capacity at its on-site Independent Spent Fuel Storage Installation (“ISFSI”) to store all of the nuclear fuel that will be irradiated during the initial operating license period, which ends in December 2027. Additionally, PVNGS has sufficient capacity at its on-site ISFSI to store a portion of the fuel that will be irradiated during the period of extended operation, which ends in November 2047. If uncertainties regarding the U.S. government’s obligation to accept and store spent fuel are not favorably resolved, APS will evaluate alternative storage solutions that may obviate the need to expand the ISFSI to accommodate all of the fuel that will be irradiated during the period of extended operation. The Clean Air Act Regional Haze In 1999, EPA developed a regional haze program and regional haze rules under the CAA. The rule directs each of the 50 states to address regional haze. Pursuant to the CAA, states have the primary role to regulate visibility requirements by promulgating SIPs. States are required to establish goals for improving visibility in national parks and wilderness areas (also known as Class I areas) and to develop long-term strategies for reducing emissions of air pollutants that cause visibility impairment in their own states and for preventing degradation in other states. States must establish a series of interim goals to ensure continued progress by adopting a new SIP every ten years. In the first SIP planning period, states were required to conduct BART determinations for certain covered facilities, including utility boilers, built between 1962 and 1977 that have the potential to emit more than 250 tons per year of visibility impairing pollution. If it was demonstrated that the emissions from these sources caused or contributed to visibility impairment in any Class I area, then BART must have been installed by the beginning of 2018. For all future SIP planning periods, states must evaluate whether additional emissions reduction measures may be needed to continue making reasonable progress toward natural visibility conditions. On January 10, 2017, EPA published in the Federal Register revisions to the regional haze rule. EPA also provided a companion draft guidance document for public comment. The new rule delayed the due date for the next cycle of SIPs from 2019 to 2021, altered the planning process that states must employ in determining whether to impose “reasonable progress” emission reduction measures, and gave new authority to federal land managers to seek additional emission reduction measures outside of the states’ planning process. Finally, the rule made several procedural changes to the regional haze program, including changes to the schedule and process for states to file 5-year progress reports. EPA’s new rule was challenged by numerous parties. On January 19, 2018, EPA filed a motion to hold the case in abeyance in light of several letters issued by EPA on January 17, 2018 to grant various petitions for reconsideration of the 2017 rule revisions. EPA’s decision to revisit the 2017 rule is not a determination on the merits of the issues raised in the petitions. On December 20, 2018, EPA released a new guidance document on tracking visibility progress for the second planning period. EPA is allowing states discretion to develop SIPs that may differ from EPA’s guidance as long as they are consistent with the CAA and other applicable regulations. On August 20, 2019, EPA finalized the draft guidance that was released in 2016 as a companion to the regional haze rule revisions. The final guidance differs from the draft in several ways. For example, the final guidance recognizes that sources already subject to BART may not need to be re-evaluated under the full four-factor analysis whereas the draft guidance encouraged states to evaluate all sources regardless of whether they were previously subject to BART. In addition, the final guidance recognizes that states may consider both visibility benefits and the cost of different control options when applying the four-factor analysis whereas the draft guidance recommended states require any control measures identified to be reasonable after considering the four-factor analysis alone. SIPs for the second compliance period are due in July 2021. NMED is currently preparing its SIP for the second compliance period and has notified PNM that it will not be required to submit a regional haze four-factor analysis for SJGS since PNM will retire its share of SJGS in 2022. PNM cannot predict the outcome of these matters with respect to Four Corners. Four Corners Four Corners Federal Agency Lawsuit – On April 20, 2016, several environmental groups filed a lawsuit against OSM and other federal agencies in the U.S. District Court for the District of Arizona in connection with their issuance of the approvals that extended the life of Four Corners and the adjacent mine. The lawsuit alleges that these federal agencies violated both the ESA and NEPA in providing the federal approvals necessary to extend operations at Four Corners and the adjacent mine past July 6, 2016. The court granted an APS motion to intervene in the litigation. NTEC, the current owner of the mine providing coal to Four Corners, filed a motion to intervene for the limited purpose of seeking dismissal of the lawsuit based on NTEC’s tribal sovereign immunity. The court granted NTEC’s motion and dismissed the case with prejudice, terminating the proceedings. In November 2017, the environmental group plaintiffs filed a Notice of Appeal of the dismissal in the U.S. Court of Appeals for the Ninth Circuit, and the court granted their subsequent motion to expedite the appeal. The Ninth Circuit issued a decision affirming the District Court’s dismissal of the case. In September 2019, the environmental groups filed a motion for reconsideration, which was denied in December 2019. On March 24, 2020, the environmental groups filed a petition for writ of certiorari in the U.S. Supreme Court seeking review of the Ninth Circuit's decision. The Supreme Court denied the petition on June 29, 2020, making the decision of the Ninth Circuit to affirm the District Courts dismissal of the case final. This matter is now complete. Carbon Dioxide Emissions On August 3, 2015, EPA established standards to limit CO 2 emissions from power plants. EPA took three separate but related actions in which it: (1) established the Carbon Pollution Standards for new, modified, and reconstructed power plants; (2) established the Clean Power Plan to set standards for carbon emission reductions from existing power plants; and (3) released a proposed federal plan associated with the final Clean Power Plan. The Clean Power Plan was published on October 23, 2015. Multiple states, utilities, and trade groups filed petitions for review in the DC Circuit to challenge both the Carbon Pollution Standards for new sources and the Clean Power Plan for existing sources. Numerous parties also simultaneously filed motions to stay the Clean Power Plan during the litigation. On January 21, 2016, the DC Circuit denied petitions to stay the Clean Power Plan, but 29 states and state agencies successfully petitioned the US Supreme Court for a stay, which was granted on February 9, 2016. The decision meant that the Clean Power Plan was not in effect and neither states nor sources were obliged to comply with its requirements. With the US Supreme Court stay in place, the DC Circuit heard oral arguments on the merits of the Clean Power Plan on September 27, 2016 in front of a ten judge en banc panel. However, before the DC Circuit could issue an opinion, the Trump Administration asked that the case be held in abeyance while the rule was being re-evaluated, which was granted. In addition, the DC Circuit issued a similar order in connection with a motion filed by EPA to hold cases challenging the NSPS in abeyance. On September 17, 2019, the DC Circuit issued an order that granted motions by various petitioners, including industry groups and EPA, to dismiss cases challenging the Clean Power Plan as moot due to EPA's issuance of the Affordable Clean Energy rule, which repealed the Clean Power Plan. On March 28, 2017, President Trump issued an Executive Order on Energy Independence. The order put forth two general policies: promote clean and safe development of energy resources, while avoiding regulatory burdens, and ensure electricity is affordable, reliable, safe, secure, and clean. The order directed the EPA Administrator to review and, if appropriate and consistent with law, suspend, revise, or rescind (1) the Clean Power Plan, (2) the NSPS for GHG from new, reconstructed, or modified electric generating units, (3) the Proposed Clean Power Plan Model Trading Rules, and (4) the Legal Memorandum supporting the Clean Power Plan. In response to the Executive Order, EPA filed a petition with the DC Circuit requesting the cases challenging the Clean Power Plan be held in abeyance until after the conclusion of EPA’s review and any subsequent rulemaking, which was granted. In addition, the DC Circuit issued a similar order in connection with a motion filed by EPA to hold cases challenging the NSPS in abeyance. On September 17, 2019, the DC Circuit issued an order that granted motions by various petitioners, including industry groups and EPA, to dismiss the cases challenging the Clean Power Plan as moot due to EPA’s issuance of the Affordable Clean Energy rule. EPA’s efforts to replace the Clean Power Plan with the Affordable Clean Energy rule began on October 10, 2017, when EPA issued a NOPR proposing to repeal the Clean Power Plan and filed its status report with the court requesting the case be held in abeyance until the completion of the rulemaking on the proposed repeal. The NOPR proposed a legal interpretation concluding that the Clean Power Plan exceeded EPA’s statutory authority. On August 31, 2018, EPA published a proposed rule, known as the Affordable Clean Energy rule, to replace the Clean Power Plan. On June 19, 2019, EPA released the final version of the Affordable Clean Energy rule. EPA takes three actions in the final rule: (1) repealing of the Clean Power Plan; (2) promulgating the Affordable Clean Energy rule; and (3) revising the implementing regulations for all emission guidelines issued under Clean Air Act Section 111(d), which, among other things, extends the deadline for state plans and the timing for EPA's approval process. The final rule is very similar to the August 2018 proposed rule. EPA set the Best System of Emissions Reduction (“BSER”) for existing coal-fired power plants as heat rate efficiency improvements based on a range of “candidate technologies” that can be applied inside the fence-line. Rather than setting a specific numerical standard of performance, EPA’s rule directs states to determine which of the candidate technologies to apply to each coal-fired unit and establish standards of performance based on the degree of emission reduction achievable based on the application of BSER. The final rule requires states to submit a plan to EPA by July 8, 2022 and then EPA has one year to approve the plan. If states do not submit a plan or their submitted plan is not acceptable, EPA will have two years to develop a federal plan. The Affordable Clean Energy rule is not expected to impact SJGS since EPA’s final approval of a state SIP would occur after PNM retires its share of SJGS in 2022. Since the Navajo Nation does not have primacy over its air quality program, EPA would be the regulatory authority responsible for implementing the Affordable Clean Energy rule on the Navajo Nation. PNM is unable to predict the potential financial or operational impacts on Four Corners. While corresponding NSR reform regulations were proposed as part of the proposed Affordable Clean Energy rule, the final rule did not include such reform measures. Unrelated to the Affordable Clean Energy rule, EPA issued a proposed rule on August 1, 2019 to clarify one aspect of the pre-construction review process for evaluating whether the NSR permitting program would apply to a proposed project at an existing source of emissions. The proposed rule clarifies that both emissions increases and decreases resulting from a project are to be considered in determining whether the proposed project will result in an increase in air emissions. On December 20, 2018, EPA published in the Federal Register a proposed rule that would revise the Carbon Pollution Standards rule published in October 2015 for new, reconstructed, or modified coal-fired EGUs. The proposed rule would revise the standards for new coal-fired EGUs based on the revised BSER as the most efficient demonstrated steam cycle (e.g., supercritical steam conditions for large units and subcritical steam conditions for small units), instead of partial carbon capture and sequestration. As a result, the proposed rule contains less stringent CO 2 emission performance standards for new units. EPA has also proposed revisions to the standards for reconstructed and modified fossil-fueled power plants to align with the proposed standards for new units. EPA is not proposing any changes nor reopening the standards of performance for newly constructed or reconstructed stationary combustion turbines. PNM’s review of the GHG emission reductions standards under the Affordable Clean Energy rule and the revised proposed Carbon Pollution Standards rule is ongoing. The Affordable Clean Energy rule has been challenged by several parties and may be impacted by further litigation. PNM cannot predict the impact these standards may have on its operations or a range of the potential costs of compliance, if any. National Ambient Air Quality Standards (“NAAQS”) The CAA requires EPA to set NAAQS for pollutants reasonably anticipated to endanger public health or welfare. EPA has set NAAQS for certain pollutants, including NOx, SO 2 , ozone, and particulate matter. In 2010, EPA updated the primary NOx and SO 2 NAAQS to include a 1-hour standard while retaining the annual standards for NOx and SO 2 and the 24-hour SO 2 standard. EPA also updated the final particulate matter standard in 2012 and updated the ozone standard in 2015. NOx Standard – On April 18, 2018, EPA published the final rule to retain the current primary health-based NOx standards of which NO 2 is the constituent of greatest concern and is the indicator for the primary NAAQS. EPA concluded that the current 1-hour and annual primary NO 2 standards are requisite to protect public health with an adequate margin of safety. The rule became effective on May 18, 2018. SO 2 Standard – On May 13, 2014, EPA released the draft data requirements rule for the 1-hour SO 2 NAAQS, which directs state and tribal air agencies to characterize current air quality in areas with large SO 2 sources to identify maximum 1-hour SO 2 concentrations. This characterization requires areas be designated as attainment, nonattainment, or unclassifiable for compliance with the 1-hour SO 2 NAAQS. On August 11, 2015, EPA released the Data Requirements Rule for SO 2 , telling states how to model or monitor to determine attainment or nonattainment with the new 1-hour SO 2 NAAQS. On June 3, 2016, NMED notified PNM that air quality modeling results indicated that SJGS was in compliance with the standard. In January 2017, NMED submitted its formal modeling report regarding attainment status to EPA. The modeling indicated that no area in New Mexico exceeds the 1-hour SO 2 standard. NMED submitted the first annual report for SJGS as required by the Data Requirements Rule in June 2018. That report recommended that no further modeling was warranted due to decreased SO 2 emissions. NMED submitted the second and third annual modeling report to EPA in July 2019 and July 2020. Those reports retained the recommendation that no further modeling is needed at this time and is subject to EPA review. On February 25, 2019, EPA announced its final decision to retain without changes the primary health-based NAAQS for SO 2 . Specifically, EPA will retain the current 1-hour standard for SO 2 , which is 75 parts per billion, based on the 3-year average of the 99th percentile of daily maximum 1-hour SO 2 concentrations. On May 14, 2015, PNM received an amendment to its NSR air permit for SJGS, which reflects the revised state implementation plan for regional haze BART and required the installation of SNCRs. The revised permit also required the reduction of SO 2 emissions to 0.10 pound per MMBTU on SJGS Units 1 and 4 and the installation of BDT equipment modifications for the purpose of reducing fugitive emissions, including NOx, SO 2, and particulate matter. These reductions help SJGS meet the NAAQS for these constituents. The BDT equipment modifications were installed at the same time as the SNCRs, in order to most efficiently and cost effectively conduct construction activities at SJGS. See a discussion of the regulatory treatment of BDT in Note 12. Ozone Standard – On October 1, 2015, EPA finalized the new ozone NAAQS and lowered both the primary and secondary 8-hour standard from 75 to 70 parts per billion. With ozone standards becoming more stringent, fossil-fueled generation units will come under increasing pressure to reduce emissions of NOx and volatile organic compounds since these are the pollutants that form ground-level ozone. On July 13, 2020, EPA proposed to retain the existing ozone NAAQS based on a review of the full body of currently available scientific evidence and exposure/risk information. The proposed rule was published in the Federal Register, on August 14, 2020. EPA anticipates a final rule in 2021. On November 10, 2015, EPA proposed a rule revising its Exceptional Events Rule, which outlines the requirements for excluding air quality data (including ozone data) from regulatory decisions if the data is affected by events outside an area’s control. The proposed rule is important in light of the more stringent ozone NAAQS final rule since western states like New Mexico and Arizona are subject to elevated background ozone transport from natural local sources, such as wildfires and stratospheric inversions, and transported via winds from distant sources in other regions or countries. EPA finalized the rule on October 3, 2016 and released related guidance in 2018 and 2019 to help implement its new exceptional events policy. During 2017 and 2018, EPA released rules establishing area designations for ozone. In those rules, San Juan County, New Mexico, where SJGS and Four Corners are located, is designated as attainment/unclassifiable and only a small area in Doña Ana County, New Mexico is designated as marginal non-attainment. Although Afton is located in Doña Ana County, it is not located within the small area designated as nonattainment for the 2015 ozone standard. The final rule also establishes the timing of attainment dates for each non-attainment area classification, which are marginal, moderate, serious, severe, or extreme. The rule became effective May 8, 2018. Attainment plans for nonattainment areas are due in August 2021. NMED has responsibility for bringing the small area in Doña Ana County designated as marginal/non-attainment for ozone into compliance and will look at all sources of NOx and volatile organic compounds. On November 22, 2019, EPA issued findings that several states, including New Mexico, had failed to submit SIPs for the 8-hour ozone NAAQS. In response, in December 2019, NMED published the Public Review Draft of the New Mexico 2013 NAAQS Good Neighbor SIP that outlines the strategies and emissions control measures that are expected to improve air quality in the area by May 8, 2021. These strategies and measures would aim to reduce the amount of NOx and volatile organic compounds emitted to the atmosphere and will rely upon current or upcoming federal rules, new or revised state rules, and other programs. Comments or requests for a public hearing were required by January 21, 2020. PNM does not believe there will be material impacts to its facilities as a result of NMED’s non-attainment designation of the small area within Doña Ana County. Until EPA approves attainment designations for the Navajo Nation and releases a proposal to implement the revised ozone NAAQS, PNM is unable to predict what impact the adoption of these standards may have on Four Corners. PNM cannot predict the outcome of this matter. PM Standard – On January 30, 2020, EPA published in the Federal Register a notice announcing the availability of its final Policy Assessment for the Review of the National Ambient Air Quality Standards for Particulate Matter (the "Final PA"). The final assessment was prepared as part of the review of the primary and secondary PM NAAQS. In the assessment, EPA recommend lowering the primary annual PM2.5 standard to between 8 µg/m3 and 10 µg/m3. However, on April 30, 2020, EPA published a proposed rule to retain the current standards for PM due to uncertainties in the data relied upon in the Final PA. EPA accepted comments on the proposed rule through June 29, 2020. EPA anticipates issuing a final rulemaking in late 2020. PNM cannot predict the outcome of this matter or whether it will have a material impact on its financial position, results of operations, or cash flows. Navajo Nation Environmental Issues Four Corners is located on the Navajo Nation and is held under easements granted by the federal government, as well as agreements with the Navajo Nation which grant each of the owners the right to operate on the site. The Navajo Acts purport to give the Navajo Nation Environmental Protection Agency authority to promulgate regulations covering air quality, drinking water, and pesticide activities, including those activities that occur at Four Corners. In October 1995, the Four Corners participants filed a lawsuit in the District Court of the Navajo Nation challenging the applicability of the Navajo Acts to Four Corners. In May 2005, APS and the Navajo Nation signed an agreement resolving the dispute regarding the Navajo Nation’s authority to adopt operating permit regulations under the Navajo Nation Air Pollution Prevention and Control Act. As a result of this agreement, APS sought, and the court granted, dismissal of the pending litigation in the Navajo Nation Supreme Court and the Navajo Nation District Court, to the extent the claims relate to the CAA. The agreement does not address or resolve any dispute relating to other aspects of the Navajo Acts. PNM cannot currently predict the outcome of these matters or the range of their potential impacts. Cooling Water Intake Structures In 2014, EPA issued a rule establishing national standards for certain cooling water intake structures at existing power plants and other facilities under the Clean Water Act to protect fish and other aquatic organisms by minimizing impingement mortality (the capture of aquatic wildlife on intake structures or against screens) and entrainment mortality (the capture of fish or shellfish in water flow entering and passing through intake structures). To minimize impingement mortality, the rule provides operators of facilities, such as SJGS and Four Corners, seven options for meeting Best Technology Available (“BTA”) standards for reducing impingement. SJGS has a closed-cycle recirculating cooling system, which is a listed BTA and may also qualify for the “ de minimis rate of impingement” based on the design of the intake structure. The permitting authority must establish the BTA for entrainment on a site-specific basis, taking into consideration an array of factors, including endangered species and social costs and benefits. Affected sources must submit source water baseline characterization data to the permitting authority to assist in the determination. Compliance deadlines under the rule are tied to permit renewal and will be subject to a schedule of compliance established by the permitting authority. The rule is not clear as to how it applies and what the compliance timelines are for facilities like SJGS that have a cooling water intake structure and only a multi-sector general stormwater permit. However, EPA has indicated that it is contemplating a December 31, 2023 compliance deadline. PNM is working with EPA regarding this issue and does not expect material changes as a result of any requirements that may be imposed upon SJGS, particularly given the NMPRC's April 1, 2020 approval for PNM to retire its share of SJGS by June 2022. On May 23, 2018, several environmental groups sued EPA Region IX in the U.S. Court of Appeals for the Ninth Circuit Court over EPA’s failure to timely reissue the Four Corners NPDES permit. The petitioners asked the court to issue a writ of mandamus compelling EPA Region IX to take final action on the pending NPDES permit by a reasonable date. EPA subsequently reissued the NPDES permit on June 12, 2018. The permit did not contain conditions related to the cooling water intake structure rule as EPA determined that the facility has achieved BTA for both impingement and entrainment by operating a closed-cycle recirculation system. On July 16, 2018, several environmental groups filed a petition for review with EPA’s Environmental Appeals Board concerning the reissued permit. The environmental groups alleged that the permit was reissued in contravention of several requirements under the Clean Water Act and did not contain required provisions concerning certain revised effluent limitation guidelines, existing-source regulations governing cooling-water intake structures, and effluent limits for surface seepage and subsurface discharges from coal-ash disposal facilities. On December 19, 2018, EPA withdrew the Four Corners NPDES permit in order to examine issues raised by the environmental groups. Withdrawal of the permit moots the appeal pending before the Environmental Appeals Board ("EAB"). EPA’s EAB thereafter dismissed the environmental groups’ appeal. EPA issued an updated NPDES permit on September 30, 2019. The permit has been stayed pending an appeal filed by several environmental groups on November 1, 2019 to EPA's EAB. Oral argument was heard on September 3, 2020. The EAB issued an order denying the petition for review on September 30, 2020. The denial was based on the EAB's determination that the petitioners had failed to demonstrate that review of the permit was warranted on any of the grounds presented in the petition. PNM cannot predict whether there will be further appeals of this matter or whether the outcome of any such appeal will have a material impact on PNM’s financial position, results of operations or cash flows. Effluent Limitation Guidelines On June 7, 2013, EPA published proposed revised wastewater effluent limitation guidelines establishing technology-based wastewater discharge limitations for fossil fuel-fired electric power plants. EPA’s proposal offered numerous options that target metals and other pollutants in wastewater streams originating from fly ash and bottom ash handling activities, scrubber activities, and non-chemical metal cleaning waste operations. All proposed alternatives establish a “zero discharge” effluent limit for all pollutants in fly ash transport water. Requirements governing bottom ash transport water differ depending on which alternative EPA ultimately chooses and could range from effluent limits based on Best Available Technology Economically Achievable to “zero discharge” effluent limits. EPA signed the final Steam Electric Effluent Guidelines rule on September 30, 2015. The final rule, which became effective on January 4, 2016, phased in the new, more stringent requirements in the form of effluent limits for arsenic, mercury, selenium, and nitrogen for wastewater discharged from wet scrubber systems and zero discharge of pollutants in ash transport water that must be incorporated into plants’ NPDES permits. The 2015 rule required each plant to comply between 2018 and 2023 depending on when it needs a new or revised NPDES permit. The Effluent Limitations Guideline |
