Fish, Sediment, Dioxin Study Completed For Salem’s Willamette Slough; State Maintains Fish Advisory for Willamette River from Eugene to Portland

Fish in Willamette Slough have similar levels of dioxins in their tissue as those in other parts of the Willamette River, according to a study approved by the Oregon Department of Environmental Quality.

Boise Cascade Corporation operated a pulp and paper mill at Willamette Slough in Salem from 1962 to 1982 and the company more recently studied dioxins in fish tissue and sediment at the request of DEQ. Dioxins refer to a group of toxic chemicals that are widespread at low levels in the environment. Industrial processes, including paper and chemical manufacturing processes may also create dioxins.

The dioxin study involved collecting additional sediment samples as well as tissue samples from fish caught in the slough and at a separate sampling location upstream along the Willamette River in 2017. The emphasis of the study was to determine if fish in the area could absorb dioxins from sediment, and if there were elevated levels of dioxins in fish from the slough compared to fish from the upstream location.

The Oregon Health Authority maintains a fish advisory for the Willamette River from Eugene to its mouth in Portland, which includes Salem and Willamette Slough, because of elevated levels of mercury present in fish tissues. Fish advisories include consumption guidelines for limiting the eating of certain fish to reduce exposure to chemicals.

DEQ coordinated with the State Historic Preservation Office, the Confederated Tribes of Grand Ronde and the Confederated Tribes of Siletz Indians during the course of the sampling for the dioxins study to gain their input and to help protect cultural resources.

A preliminary DEQ study in 2016 found elevated levels of dioxins in sediment in Willamette Slough. Out of an abundance of caution, the department worked with the City of Salem to warn anglers of possible contamination that could affect fish caught from Willamette Slough. DEQ has advised the city it can remove warning signs because the study shows eating fish caught in the slough is no different than eating fish caught elsewhere in the Willamette.

Salem has been leading revitalization of land around Willamette Slough, including the completion of The Peter Courtney Minto Island Bicycle and Pedestrian Bridge in 2017 and ongoing construction of a riverside amphitheater. The bridge spans the slough and connects downtown Salem to Minto-Brown Island Park.

Go to to view the study results and other documents related to the former mill site.

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