WASHINGTON - A coalition of activist groups called Monday for Congress to authorize an independent and comprehensive study of whether the Columbia River as it flows through the Hanford reservation has been contaminated with radioactivity and other toxins.

In a letter to Rep. Norm Dicks, D-Wash., the groups said Department of Energy studies of the extent of contamination on the Hanford Reach and its effect on wildlife, particularly salmon, are suspect, and they said an outside agency needs to oversee a new effort.

"Since various current reports on the contamination of the river give conflicting results, a trustworthy and impartial researcher is needed to do a complete study of the legacy of contamination in the river today, the threats for the future and the risks involved in failing to fully clean up Hanford," the letter said.

Dicks is a senior member of the House Appropriations Committee and has worked to provide funding to protect endangered salmon runs on the Snake and Columbia rivers and elsewhere throughout the region.

The letter was signed by nine groups, including the Government Accountability Project, Heart of America Northwest, the Pacific Coast Fisherman's Association and the Washington Environmental Council.

The Hanford Reach, which stretches more than 50 miles from the Vernita Bridge to Richland, was designated as a national monument several years ago. It provides a spawning ground for wild salmon.

"There needs to be a credible assessment of the danger to the river and its resources," said Gerald Pollett, executive director of Heart of America Northwest.

Pollett and Tom Carpenter, director of the Government Accountability Project's nuclear oversight program, were in Washington, D.C., with 80 other activists for three days of lobbying on nuclear issues.

In the mid-1990s, Carpenter said, DOE appointed a team of representatives from Washington state, Oregon, the federal Environmental Protection Agency and various tribes to help determine how to proceed with a comprehensive study of the river. But after two years of work, Carpenter said, the department decided not to proceed.

"DOE dropped it," Carpenter said. "DOE doesn't want to know the extent of the problem."

EPA, the U.S. Geological Survey, the National Academy of Sciences or the University of Washington could lead a new study, he said.

More than 1 million people downstream from Hanford get their drinking water from Hanford, the river supplies water for irrigation and 80 percent of the wild salmon on the Columbia River spawn in the Hanford Reach, Carpenter said.

In addition, Carpenter said about 80 square miles of ground water underneath Hanford has been polluted by an estimated half a trillion gallons of radioactive and toxic liquids dumped or leaked into the soil during 50 years of nuclear weapons production at Hanford.

DOE has insisted any contamination reaching the river is minimal and is quickly diluted.

Barnett said the Pacific Northwest National Laboratory monitors the river and releases an annual report.

But in their letter to Dicks, the groups said studies of the river done by DOE contractors have "serious flaws and are not considered credible by many Hanford stakeholders."

Carpenter and Pollett are scheduled to meet with Dicks this week.