Farmers and foresters in Oregon’s Willamette Basin would be expected to reduce mercury pollution by 88% under proposed rules drafted by state environmental regulators.
That target is part of the Oregon Department of Environmental Quality’s revised “total maximum daily load” regulation for mercury pollution in the basin that must be complete by late November to comply with a federal court order.
“Over the near term, we’re looking at progress, not perfection,” said Gene Foster, DEQ’s watershed program manager.
Soil erosion is the primary pathway that allows mercury to enter waterways from farms and forests, but much of the pollutant originates from coal burned in China and is deposited in Oregon through rain.
“Non-point” sources of pollution, including the farming and forestry industries, are considered major mercury contributors in the Willamette Basin and would face an 88% reduction in their “load” under DEQ’s draft proposal.
The goal is to reduce the current median amount of mercury in fish tissue from 0.15 milligrams per kilogram to 0.04 milligrams per kilogram under an updated TMDL ordered by a federal judge in 2017.
However, that task is complicated by uncertainty about the amount of mercury that would leach into water regardless of human pursuits.
“We can’t parse out what is happening naturally on the landscape and what is occurring due to anthropogenic (human) activities,” said Foster of DEQ during an April 26 meeting in Portland.
Agriculture and forestry groups have worried they’ll be responsible for decreasing mercury pollution to levels that wouldn’t be achievable even if their industries completely stopped operating.
While the amount of “atmospheric deposition” of mercury is outside the DEQ’s control, the agency believes there’s a general trend toward renewable energy and away from coal-burning power that’s responsible for the pollutant, Foster said.
“It’s not enforceable by the state of Oregon,” he said.
Reducing erosion will help curtail mercury levels in fish tissue even with the atmospheric deposits, he said.
In the past, TMDL regulations for bacteria have achieved comparable reductions in waterways, Foster said.
For the farm and timber industries, the changes will be implemented by the Oregon Department of Agriculture and the Oregon Department of Forestry, Foster said. “It’s basically keeping soil on the land.”
The ODA would continue regulating pollution through its agricultural water quality program but set measurable objectives and milestones specific to mercury, such as reducing sediment loading during irrigation or improving upland conservation practices within a specific amount of time.
Similarly, the ODF may focus on improving compliance with forest practice rules aimed at reducing erosion. Federal agencies would also set such goals for the land they manage.
Achieving an 88% reduction in mercury discharge would require a “maximum effort” but the ODA would promote certain practices — such as cover crops and reduced tillage — rather than mandating them, said Paul Measeles, a hydrologist with the agency.
“There’s potential to be doing more practices like that in the valley,” he said. “We won’t dictate how someone deals with it but we would want to see them improve.”