US EPA Approves Ohio’s Maumee Watershed Nutrient TMDL


The city of Toledo viewed from a trail along the river.

On September 28, 2023, US EPA announced its final review and approval of the Maumee River Watershed Nutrient Total Maximum Daily Load (Maumee TMDL), which Ohio EPA submitted for approval on June 30, 2023. In issuing its approval, US EPA determined that the Maumee TMDL satisfies all statutory and regulatory requirements of an approvable TMDL.

The Maumee TMDL was developed primarily to address nutrient loading and the persistent presence of harmful algal blooms (HABs) in the western basin of Lake Erie. It addresses the portion of the Maumee River Watershed located within Ohio encompassing parts of 18 counties in northwestern Ohio. The Maumee TMDL sets the total amount of phosphorus that the western basin of Lake Erie can receive, and allocates that phosphorus load between point sources (e.g., wastewater treatment plants) and nonpoint sources (e.g., agricultural runoff) located within the Maumee River Watershed.

US EPA states that the Maumee TMDL is one tool among numerous ongoing efforts to address HABs in the Western basin of Lake Erie, which include funding from the Great Lakes Restoration Initiative and increased efforts of the Western Lake Erin Basin Partnership. 

The Maumee TMDL has received criticism for targeting total phosphorus rather than dissolved reactive phosphorus, which US EPA acknowledges has the most direct and immediate effect on promoting plant and algae growth. US EPA states that it expects Ohio to use all tools at its disposal, including regulation and enforcement, to reduce dissolved reactive phosphorus loadings to the greatest extent practicable throughout the watershed, noting “as the data and science progress, so too must Ohio’s efforts to control release” of dissolved reactive phosphorus. The Maumee TMDL has further received criticism for imposing only voluntary controls on nonpoint sources, specifically agricultural sources. US EPA acknowledges that the reduction and elimination of HABs depends on increased engagement and controls by concentrated animal feeding operations (CAFOs) in the basin, which according to US EPA contribute 10% to 12% of nutrient loading in the basin. 

Lastly, US EPA forewarns that Ohio’s ongoing monitoring efforts will document whether loading reductions are achieved and whether the Maumee TMDL proves successful, and that if impaired uses are not restored, the calculations and assumptions underlying the Maumee TMDL must be reconsidered.

As discussed in prior Bricker Graydon posts, Ohio agreed to develop the Maumee TMDL in response to litigation initially filed against US EPA by the Environmental Law and Policy Center, which was pending before Judge James Carr in the U.S. Federal Court, Northern District of Ohio (Toledo) for the past six years. A Consent Decree settling the litigation was approved by Judge Carr earlier this year, which established timelines and parameters by which Ohio EPA and US EPA must issue is the final Maumee TMDL.


Transmittal Letter For EPA’s Approval of Ohio’s Maumee Watershed Nutrient TMDL

Decision Document For The Maumee Watershed Nutrient TMDL, In All Or Parts Of 18 Counties in Northwestern Ohio

Attachment #1 of Decision Document: Maumee Watershed Nutrient TMDL Tables

Attachment #2 of Decision Document: EPA Review of Dissolved Reactive Phosphorus Information

Attachment #3 of Decision Document: EPA Review of Concentrated Animal Feeding Operation Information

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