1896 Trail, Canada facility built as a copper and gold smelter.
1906 Trail, Canada facility converted to lead and zinc smelter.
1900-1922 Mining, milling, and smelter activities active in both Canada and the United States, all of which discharge metals into the Upper Columbia and its tributaries. Smelters permanently close at Northport, Grand Forks, Greenwood, and Boundary Falls.
1930s International Joint Commission holds Trail Smelter in Canada liable for sulfur dioxide air emissions causing property damage in Washington.
1931 A new Canadian fertilizer plant built to reduce sulphur dioxide emissions becomes a primary source of phosphate discharges into the Columbia.
1942 Grand Coulee Dam gates close, raising the waters behind the dam 380 feet. Water flows and bank erosion change, affecting depositional patterns of sediment contamination.
1960 Celgar Pulp Mill begins operation.
1990-1993 WA Department of Ecology (Ecology) monitors dioxin, furan and trace metal concentrations in suspended particulate matter and fish tissues. The Celgar pulp mill is considered the primary historical source for dioxin and furan contaminants. Celgar plant modernization designed to end discharges of dioxins and furans into the Columbia.
1992 The USGS conducts a sediment study of Lake Roosevelt describing the transport of metals, the presence of trace metals in bed sediment, and the toxicity of the sediment to benthic invertebrates.
1993 Ecology initiates studies resulting in Lake Roosevelt being placed on the federal Clean Water Act Section 303(d) list of impaired water bodies.
1994 Canadian fertilizer plant ceases discharge of phosphate into the Columbia.
1994 The USGS conducts a fish tissue study to determine the level of mercury and other metals in walleye, smallmouth bass, and rainbow trout. Based on findings, a fact sheet from the Washington State Department of Health (WDOH) advises the public to limit consumption of walleye.
1995 Discharges of slag from Trail smelter cease.
1997 Teck implements Trail Modernization Program to further improve quality of effluent (wastewater) being discharged.
1998 In Canada, wide area human and ecological risk assessment initiated from Castlegar to the U.S. border.
1998 USGS conducts a follow-up fish tissue study and finds that concentration levels of metals had either not changed or decreased. Ecology identifies temperature, total dissolved gas, mercury, PCBs and pH as parameters for Lake Roosevelt inclusion on the Clean Water Act 303(d) list of impaired water bodies.
1999 Colville Confederated Tribes petition EPA to conduct an assessment of environmental contamination in Lake Roosevelt under federal Superfund program.
2001-2003 EPA collects samples of river sediments. EPA recommends a Remedial Investigation Feasibility Study (RI/FS) to assess environmental and human health risks.
2002-2006 USGS collects data to determine concentrations of trace metals in wind blown dust.
2003 After negotiations between EPA and Teck Cominco reach an impasse, EPA issues Unilateral Administrative Order under U.S. Superfund law to fund and conduct aspects of the RI/FS. Teck Cominco contests the order and EPA moves forward with the RI/FS using U.S. government funding.
2004 Canadian government issues a "Diplomatic Note" to the U.S. State Department regarding EPA enforcement order. United States and Canadian governments begin discussions regarding site.
2004 Colville Confederated Tribes and Washington State ask U.S. District Court to force Teck Cominco to comply with EPA order issued in 2003.
2004 Ecology updates Clean Water Act 303(d) impairment list for Lake Roosevelt to include temperature, total dissolved gas, and mercury.
2005 EPA RI/FS studies begin by initiating sediment sampling and fish tissue studies.
2006 EPA reaches an agreement with Teck Cominco to conduct an RI/FS that Teck Cominco will fund. Teck required to develop EPA approved RI/FS ecological work plan before studies can continue.
2006 Ninth circuit upholds a district court ruling that Superfund (CERCLA) law does apply to Teck's Trail smelter.
2008 Lake Roosevelt fish advisory updated.
2009 RI/FS ecological and human health work plans approved by EPA. Teck Cominco (now called Teck) begins RI/FS studies.