The findings are important because the Hanford Reach, a 51-mile stretch of the Columbia running past and through the nuclear reservation, is the spawning grounds for 80 percent of the river basin's remaining wild fall chinook. Those fish, whose numbers have exceeded 150,000 in recent years, are the mainstay of the Columbia's sport and tribal fisheries. The federally funded study found that levels of hexavalent chromium up to 266 parts per billion do not kill salmon eggs or young salmon or cause deformities. Although hexavalent chromium levels as high as 400 parts per billion have been found in a spring seeping into the river, chromium has never been found at levels above 130 parts per billion in the river gravel where salmon spawn. Although the drinking water standard for chromium is 100 parts per billion and the standard for protecting aquatic organisms is even more stringent, at 11 parts per billion, the study found that the higher levels of chromium did not harm developing salmon.
Hexavalent chromium is a toxic chemical added to water used to cool reactors.
Huge volumes of cooling water were used, and the spent coolant was discharged into the river or into the ground, contaminating the ground water. Hexavalent chromium is one of the two chemicals or radioactive elements leaking into the Columbia from the site that Hanford managers are most worried about. The other is strontium-90, a radioactive element that has leaked into cooling water used in nuclear reactors. Hanford officials said that neither has been found at levels that would threaten fish. But a scientist who works for a Seattle-based advocacy group said thorium, another radioactive element from Hanford, is present in the riverbed at levels high enough to threaten fish.