Spokane River PCB TMDLs

On October 29, 2024, EPA released its final TMDLs for PCBs in the Spokane and Little Spokane Rivers. Additional information is available below, including copies of the final TMDL documents, public comments received, and EPA's responses to public comments.

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Project Summary

EPA has established Total Maximum Daily Loads (TMDLs) – often referred to as a "pollution budget" – to reduce the amount of polychlorinated biphenyls, or PCBs, in the Spokane and Little Spokane Rivers in Washington.

While PCBs were banned in 1979, they were widely used by multiple industries to lubricate and cool equipment. Some of that equipment, like electrical transformers manufactured before the ban, are sources of the chemicals found in the 100 river miles of the Spokane River watershed.

PCBs in surface water readily accumulate in aquatic organisms, meaning even small amounts in the environment can pose health problems for people who consume fish.

We developed these TMDLs to fulfill our obligation under a legal agreement, called a consent decree, between EPA and two plaintiffs – the Sierra Club and the Center for Environmental Law and Policy.

We published a draft TMDL document and held a 60-day public comment period from May 15 through July 15, 2024. We received 148 pages of comments from 13 entities (see public comments below).

The resulting TMDLs will aim to restore water quality by determining the allowable amount of pollutants from all sources of PCBs in the watershed.

TMDL Documents

Public Comments

EPA accepted public comments on the draft TMDLs from May 15 through July 15, 2024. Copies of the comments we received are available in the document below. EPA's responses to the comments are included in Appendix F of the TMDLs.

EPA also held an informational meeting on May 29 to discuss the draft TMDL documents in detail, including an overview presentation followed by discussion. The meeting was available in-person, online, or by phone. For a copy of EPA's presentation from the meeting, contact Jason Pappani (pappani.jason@epa.gov).

Webinar Series

From March 2023 to January 2024, EPA hosted a series of quarterly webinars to provide project updates to interested parties. Below are summaries from each of the webinars. For copies of EPA's presentations from the webinars, contact Jason Pappani (pappani.jason@epa.gov).

January 2024 Webinar

This webinar focused on relatively recent (i.e., post-2010) surface water PCB monitoring data, an evaluation of target PCB loading capacities along the entire Washington length of the Spokane River, and a refined allocation approach based on assigning most PCB sources loads equivalent to achieving the Spokane Tribe of Indians standard of 1.3 pg/L at the point of discharge or confluence with the Spokane River.

  • Spokane and Little Spokane surface water PCB concentrations are generally at least an order of magnitude higher than applicable water quality standards (and often multiple orders of magnitude higher).
    • >45% of samples are above the Idaho standard (190 pg/L).
    • >98% of samples are above the Washington standard (7 pg/L).
    • >99% samples are above the Spokane Tribe of Indians standard (1.3 pg/L).
  • Loading capacities have been estimated at nearly 30 points along the entire Washington length of the Spokane River, which allows more precise estimates of cumulative loading capacities for individual PCB-impaired assessment units than a single value could.
  • An allocation approach that assigns 48% of the loading capacity to the upstream boundary condition at the Washington/Idaho border, 36% of the loading capacity to groundwater and diffuse inflow, 14% of the loading capacity to major tributaries, and 2% of the loading capacity to point sources both achieves applicable water quality standards and meets TMDL Reasonable Assurance requirements.

September 2023 Webinar

This webinar focused on critical river flow conditions appropriate for TMDLs that address human health issues, point source and nonpoint source TMDL Reasonable Assurance consideration requirements, and possible loading allocations that meet water quality standards for the Spokane and Little Spokane Rivers PCBs TMDLs.

  • The harmonic mean river flow should be used as the critical river condition for calculation of TMDL load allocations since human health criteria are based on long term exposure.
    • Using arithmetic mean river flow would result in drastic underestimates of Spokane and Little Spokane River pollutant concentrations downstream of pollutant sources.
  • In TMDLs that address both point and nonpoint sources of pollution, Reasonable Assurance that nonpoint source loads will be achieved must be demonstrated.
    • If nonpoint source pollution reductions are not met, additional pollution reductions from point sources becomes necessary.
  • Equitably allocating both point (i.e., Wasteload Allocation) and nonpoint (i.e., Load Allocation) pollution sources limits equal to the Spokane Tribe of Indians total PCB water quality standard of 1.3 pg/L, along with a discussion of steps that can be taken to meet the nonpoint limits, is one allocation approach that both meets applicable water quality standards and satisfies the TMDL’s Reasonable Assurance requirements.

June 2023 Webinar

This webinar focused on the analytical framework EPA is using to determine the maximum loads of PCBs that can be assimilated by the Spokane and Little Spokane Rivers, as well as the PCB load reductions necessary to attain water quality standards and protect human health.

  • Two spreadsheet models based on synoptic river survey PCB monitoring data and recent river hydrology are being developed.
    • One model will be used to estimate the maximum PCB loads that can be assimilated by the rivers while still achieving the Spokane Tribe of Indians standard of 1.3 pg/L at the upstream reservation boundary.
    • One model will be used to estimate the PCB load reductions from recently observed levels necessary to achieve the Spokane Tribe of Indians standard of 1.3 pg/L at the upstream reservation boundary.
  • Preliminary analysis shows that Spokane River PCB concentrations at the Washington/Idaho border must be below the Washington state water quality standards to achieve the Spokane Tribe of Indians water quality standards at the upstream reservation boundary.
  • Both spreadsheet models, as well as model guidance, will be made available for public review and feedback in July 2023.
  • We welcome and encourages suggestions on how to improve both models once they are made publicly available.

March 2023 Webinar

This webinar provided an overview of the project including information on PCB manufacture, use and health risks, the litigation that led to EPA being tasked with development of these PCB TMDLs, the geographic scope of the project, the environmental monitoring data available, and the relevant PCB water quality standards.

  • PCB manufacturing was banned in the U.S. in 1979, but legacy and inadvertently generated PCBs from a broad array of applications are still making their way into the environment.
  • PCBs are classified by the EPA as probable carcinogens, and there is a growing body of evidence that points to additional negative human health impacts.
  • EPA is developing TMDLs for all reaches of the Spokane and Little Spokane Rivers listed as PCB impaired in Washington’s 2018 Integrated Report to satisfy a February 2022 litigation consent decree.
  • Three PCB water quality standards exist in the watershed to protect human health, but the TMDL targets will ensure the Spokane Tribe of Indians standard of 1.3 pg/L will be achieved at the upstream reservation boundary.
  • A conservative mass balance approach that assumes no PCB degradation and provides an implicit margin of safety will be used to calculate the TMDLs.

Contacts

For questions, please contact Jason Pappani (pappani.jason@epa.gov), 208-378-5756.

For more information related to this project, visit:

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Last updated on October 29, 2024