Forests and farmland are identified as the major sources of mercury pollution in the Willamette basin’s waterways in a modeling study commissioned by Oregon’s environmental regulators.
The finding reflects the extent to which agriculture and timber are major land uses in the region and doesn’t necessarily blame them for causing pollution.
Nonetheless, Oregon’s natural resource industries are troubled by the implication they’ll be expected to shoulder most of the regulatory burden to reduce the mercury load.
“It will have a serious effect on people’s bottom lines for a problem they’re not even creating,” said Mary Anne Cooper, public policy counsel for the Oregon Farm Bureau.
Mercury is a neurotoxin that’s naturally found in the soil but also travels through the air from coal-burning plants in China and gets deposited on the ground in Oregon through rain.
Forestry and agriculture advocates are troubled by a modeling study conducted by Tetra Tech, an environmental consulting firm hired by Oregon’s Department of Environmental Quality.
The study indicates environmental regulation can’t control the major cause of mercury pollution, since it’s coming from overseas, but it can address the “fraction of the load that reaches streams” through erosion.
“You can’t achieve the target concentration without addressing the atmospheric deposition,” said John Butcher, an environmental engineer at Tetra Tech, during a Sept. 19 meeting in Wilsonville, Ore.
At this point, the modeling study is simply Tetra Tech’s opinion, rather than official DEQ policy.
However, since the U.S. Environmental Protection Agency and Oregon’s DEQ — which enforces federal water quality standards — cannot stop China from burning coal, natural resource industry advocates worry they will be expected to solve a problem they didn’t cause.
Due to the steep reduction in mercury pollution that DEQ determined was necessary to comply with the Clean Water Act, it’s possible that even the most stringent restrictions on tilling and logging wouldn’t sufficiently lower mercury levels in fish.
Activities that disturb the soil lead to erosion, with the mercury-laden sediment winding up in waterways.
The median concentration of mercury in fish tissue is currently 0.15 milligrams per kilogram. Under the “total maximum daily load” determined by DEQ, the maximum level of mercury would have to fall to 0.04 milligrams per kilogram.
Atmospheric deposition is estimated to contribute 34 percent of the Willamette basin’s mercury load, while sediment contributes to about 43 percent — however, much of the mercury in that sediment comes from historic atmospheric deposits.
In the context of land use, the model estimates that forestland represents 45 percent of the mercury load source, followed by shrubland — which is mostly disturbed forests — at 20 percent.
Row crops were found to represent 7 percent of the load source, while the “other” category — which includes pasture and hay ground — was estimated at 11 percent. Altogether, these sources represent 83 percent of the mercury load.
Heath Curtiss, government affairs director for the Oregon Forest Industries Council, fears it’s possible that even if all forestry and farming were shut down in Oregon, mercury pollution would still exceed the DEQ’s standard.
“This water quality modeling proves this standard is unattainable,” he said. “There is literally nothing we can do to meet those target reductions.”
Arguably, farms and forests are actually “sequestering” much of the mercury by capturing the element in soil and plants, preventing all of it from going directly into waterways, said Mary Anne Cooper of the Oregon Farm Bureau.
The modeling study doesn’t acknowledge the erosion-prevention measures that farmers have already taken, she said. “It doesn’t take into account cover cropping, it doesn’t take into account riparian buffers, it doesn’t take into account restoration work or conservation tillage.”
Objections were also raised about the data used in the modeling study, much of which was collected in the 1990s, before such methods were as commonly employed by Oregon’s farmers and foresters.
“I had hair in the 1990s, which has very little relevance for today,” said Jeff Stone, executive director of the Oregon Association of Nurseries.
Gene Foster, DEQ’s watershed management manager, said the agency won’t ignore the strides made by natural resource industries in controlling erosion.
“We recognize a lot has happened to keep soil on the land over the past years,” he said. “We will be able to take those into account in our water quality management development.”
The EPA and DEQ are under a tight court-ordered deadline to revise how the state deals with mercury pollution.
In 2017, a judge ruled the way that EPA and DEQ had decided to implement the “total maximum daily load” standard was insufficiently strict and gave the agencies two years to revise their methods. That deadline is coming up next April, which is why DEQ has commissioned the modeling study and assembled an advisory group to confer on its plans.
At this point, the modeling study hasn’t identified which sources of mercury pollution are human-caused or would occur without logging or tilling, Foster said. The study currently differentiates among land use sources of the mercury load regardless of human activity.
Though it’s unclear whether the water quality standard can be achieved through regulation, the modeling study is the best science available to the agency, he said.
As the state implements the TMDL standard to reduce the mercury load, regulators will monitor the basin water system and respond with “adaptive management,” Foster said.
“As things progress, we learn more and adapt accordingly,” he said.