DEQ outlines TMDL history and next steps for North Fork Payette subbasin; seeks local advisory group input

The Idaho Department of Environmental Quality on Monday reviewed the Total Maximum Daily Load (TMDL) process for the North Fork Payette River subbasin and requested local participation as it prepares new TMDLs and five-year reviews for impaired streams and reservoirs.

Vanessa Johnson, a DEQ staff member, told the Valley County Board of Commissioners that the agency submitted the draft 2024 Integrated Report to the U.S. Environmental Protection Agency and is awaiting EPA approval. "Once listed on the integrated report, a TMDL is written to address each of the pollutants causing the impairments in the category 5 waters," Johnson said.

Johnson said DEQ’s work in the North Fork Payette subbasin dates back to the mid-1990s and includes watershed management plans, TMDLs, implementation plans and five-year reviews. "There has been TMDLs written or watershed management plans written for nutrients, pH, dissolved oxygen, sediment, and temperature impairments," she said, summarizing documents from 1996, 1998, 2000, 2009, 2011 and 2018.

Why it matters: The subbasin includes North Fork Payette River above and into Payette Lake and is divided into 78 assessment units. Johnson said 17 units previously addressed are in category 4A, and the 2024 draft integrated report lists 10 assessment units as category 5 — impaired and requiring a TMDL. Pollutants noted in the presentation include sediment, temperature, phosphorus, combined biota impacts, pH, dissolved oxygen, E. coli and mercury.

Johnson described the TMDL workflow: listing on the biennial integrated report, development of TMDLs that set load capacities, later preparation of implementation plans identifying recommended actions and schedules, and five-year reviews that evaluate whether targets and load allocations remain appropriate. She highlighted the portions of the process that require involvement from local watershed advisory groups (WAGs).

During questions, commissioners and attendees pressed DEQ on the apparent lack of substantive water-quality improvement in some areas despite decades of planning. "I recognize it's disheartening to see that we've been writing TMDLs for 30 years," Johnson said. She explained that TMDLs establish a technical framework and that recommended best management practices for nonpoint sources are typically voluntary, while point sources are regulated through permits (IPDES).

On mercury listings in Payette Lake, DEQ staff said the impairment is based on older fish-tissue data. Lance (surname not provided) explained that a 2005 statewide fish-tissue study found mercury in older trout, which accumulate mercury over long lifespans, and that listing is not necessarily tied to a current point-source discharge: "There's not like a load from a point source or an unplanned source really detected in the watershed," he said.

Commissioners and attendees also raised wildfire effects and background/natural sources. An attendee asked whether DEQ separates natural events such as wildfire ash from human-caused pollutant sources. Johnson said the TMDL process determines sources of impairment; DEQ documents pre-fire and post-fire conditions where data exist and will account for natural events in its assessments.

Participants discussed known local sources of phosphorus, including legacy sediment and sewage systems. Johnson and Lance referenced historic efforts to reduce point-source phosphorus — including past changes at hatcheries and sewer reuse projects — and noted a continuing nonpoint-source load and internal recycling of phosphorus from reservoir sediments. One participant mentioned an existing leak in the local sewer lagoons; DEQ staff said the sewer district has pursued repairs that should reduce the phosphorus load.

Local officials asked whether DEQ provides funding for monitoring and source testing. Johnson said she contacted DEQ’s grants and loans program and "it didn't sound like there was any kind of monitoring-specific funding that we had available." An attendee noted a single source test can cost about $1,500.

Next steps: Johnson said DEQ would like to re-form the North Fork Payette River Watershed Advisory Group to bring local knowledge into TMDL development and five-year reviews. She cited Idaho statutes governing TMDLs and WAGs (Idaho Code 39-36-11, 39-36-15, 39-36-16) and offered to add interested people to an email list. "Establishing the WAGs and working with them throughout this process is vital to DEQ," she said.

Board follow-up and context: Commissioners said they will consider whether a county commissioner should serve on the regional WAG and noted the lengthy timeline for water-quality improvement. Johnson offered to provide her presentation and supporting documents on request.

Public comment: At the meeting’s public-comment portion, Dan Welch of McCall spoke briefly to thank county staff and planners for their work.

The session did not include any formal votes on TMDLs or funding; DEQ’s request was for local engagement in upcoming advisory-group work and data review.