Mac enters third year of program to monitor mercury in waterways

The city of McMinnville recently completed the second year of a state-mandated program to monitor mercury levels in waterways. Engineering staff provided an update to City Council Wednesday on the plan, which focuses more on soil than water.

In 1998, salmon in the Willamette Basin were found to have elevated levels of mercury. The Oregon Department of Environmental Quality developed Total Maximum Daily Load (or clean water plans) in 2006 and revised the program to include the Yamhill River in 2021. The city was identified as the Designated Management Agency for the river and started a five-year implementation plan in 2022 that includes public education and mitigation efforts, according to Public Works Director Geoff Hunsaker.

Much of the mercury that can be harmful to both wildlife and humans is carried across the Pacific Ocean from overseas industries such as coal, industrial manufacturing and precious metal mining, and brought to Oregon in the form of rain, according to Engineering Technician Logan Adams. The TMDL plan is focused on erosion due to chemical reactions from mercury and soil.

“When it rains about 20% of it is then deposited in lakes, rivers, streams and there’s not a lot we can do about that. But when it falls on the Earth it chemically reacts with soil particles,” Adams said.

Soil particles have a negative charge and bind easily with mercury, which has a positive charge, according to Adams.

“The issue comes then when that soil or organic matter is eroded or flushed away into a lake, river or stream,” he said. “So we are talking about a mercury TMDL and mercury is the thing we’re trying to reduce, but the implementation plan is really more of an erosion control implementation plan because what we’re trying to do is to stop that soil or organic matter that has been contaminated with mercury from reaching a water source and we do that by preventing erosion.”

If the contaminated soil reaches water sources it is consumed by microbes and phytoplankton that turn normal mercury into methyl mercury, which becomes dangerous, Adams said.

“Its combination with hydrogen and carbon essentially allows it to disguise itself … as organic matter. It passes through a lot of the membranes both in fish bodies and in human bodies that are normally protected,” he said.

The problem grows as fish eat the microbes and are then eaten by larger fish, leading to bioaccumulation, Adams said.

“Each level up on the food chain is receiving a magnitude or an order of magnitude more mercury based off of what it’s eating,” he said. “And then eventually it gets to humans.”

Mercury poisoning can lead to physical and cognitive issues through the degradation of the central nervous system and it is especially dangerous for children, pregnant women and the elderly, Adams said.

“Most of the ill effects that you see from mercury poisoning are that it essentially attacks the central nervous system,” he said. “It’s able to pass into the brain.”

The problem is a health concern that also impacts Oregon’s commercial fishing industry because if people fear mercury poisoning, they will be less likely to consume fish, Adams said.

The city’s DEQ-approved plan has six control measures: public outreach and involvement, contaminant spill response and reporting, managing runoff from construction sites during and after a project and ensuring city operations follow the same practices, according to the TMDL.

Currently, construction projects over one-acre are required to obtain a state-level permit that includes an extensive erosion control plan. The city will also have to pass ordinances to locally manage construction sites between a half-acre and an acre and implement enforcement measures for anyone found dumping in waterways, Hunsaker said.

In 2027, the city will submit an evaluation to DEQ covering the city’s steps and whether the TMDL met its goals and if those goals were beneficial, Hunsaker said.

DEQ will provide feedback and will likely require additional measures and stricter monitoring for the next five-year iteration of the plan, Hunsaker said.

The city didn’t formally adopt the plan when it began in September 2022 and council agreed to adoption at an upcoming meeting as a housekeeping measure. No votes were taken at the work session.

City expands information, seeks public’s help

“If somebody is putting something into the stormwater system other than rainwater, we need to have the authority to act on that,” said Logan Adams, engineering technician with the city.

The city of McMinnville’s mercury monitoring and control ordinances are scheduled for enactment next year or 2026, but the city has been busy with other aspects of the plan, including producing a resource portfolio for residents that is available at city buildings.

The city’s street sweeping and catch basin cleaning are now required as part of the mercury Total Maximum Daily Load program, and there are more inspections being done on city facilities, Hunsaker said.

The city is looking for volunteers to mark catch basins as no dumping areas, and has conducted public outreach events at Linfield University and McMinnville High School.

The city has two stream restoration projects, with one underway on the portion of Cozine Creek that runs through City Park, Adams said. An invasive species was found on the creek bank and a plan has been developed to remove it and plant native species to stabilize the soil that had begun eroding.

“It’s cool to be able to see the science behind it and it’s also cool to see that impact, because it’s going to be improving City Park,” he said.