Turbid water plumes in Marys River

Drone footage of Marys River at west end of Avery Park
Thursday, June 10, 2021

Update 6/15/21 at 2:57 p.m.: The Oregon Department of Environmental Quality and the Oregon Department of Geology and Mineral Industries are pursuing enforcement on a water quality standard violation that resulted in the plume of turbid water that was discharged into the Marys River.

The plume of turbid water has been diluted in the Willamette River and the quarry has taken corrective actions to prevent further discharges. There have been no reports of any fish kills along the Mary’s and Willamette rivers, according to the Oregon Department of Fish and Wildlife.


Update 6/11/21 at 3:15 p.m.: Jurisdictions north of Benton County have been notified, and the plume should continue to disperse over the next 72 hrs. State and local officials confirmed that a second plume will not occur in the Marys River.


Update 6/11/21 at 10:13 a.m.: The first plume has passed from the Marys River into the Willamette River, where it is expected to disperse over the next 72 hours with assistance from forecasted rain.

Benton County notified local municipalities today of a bank-to-bank plume of fine particulate matter and sediment located in the Marys River between Philomath and Avery Park in Corvallis, Oregon. At this time, no municipal water systems are impacted.

The turbid water plume resulted from water overflow during standard basalt blasting that occurred north of Marys River Estates. The Oregon Department of Environmental Quality responded to this overflow incident immediately.

The plume reached the City of Philomath’s municipal water intake around 1:00 a.m. on Wednesday morning. The intake system functioned properly and shut down before allowing sediment into the city’s water supply. City staff cleared the blockage of sediment and the system returned to full use. The city’s water supply was not impacted.

Following the water outflow event, the quarry immediately performed mitigation to prevent further spillage. Unfortunately, a second overflow incident occurred around 1:00 p.m. on Thursday afternoon and another turbid water plume in the Marys River was spotted west of Philomath. 

The City of Philomath intends to shut down the intake system on the Marys River and tie-in with the City of Corvallis for water supply. County staff continue to work to identify the length and location of the second turbid water plume.

Benton County continues to follow the guidance of the Department of Environmental Quality (DEQ) and to track the flow of the plume through waterways.

The County advises the public to avoid swimming and recreating in the Marys River until further notice.

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Marys River at Bellfountain Bridge
Marys River from Bellfountain Bridge
Turbid Water in Marys River
Turbid Water in Marys River