Environmental studies will determine when and how Gold Ray Dam will come down.

Gold Ray Dam could be out of the upper Rogue River in 2012 and replaced with world-class kayaking rapids under Jackson County's best-case scenario for the last great barrier to fish and boats between the Cascades and the sea.

Contractors next week should begin the first phases of studying the muck that's been trapped behind the dam near Gold Hill for 104 years. The federally required sediment study will determine whether, when and how the dam is removed, county officials said.

Sonar pulses pumped into the silt and rock will determine how deep the sediment is atop bedrock in the reservoir behind the dam.

It is the next phase of a contract the county signed last week with DHR Engineering, said Lin Bernhardt, the county's natural resources coordinator.

That will be followed by studies of the area's geomorphology before the original wooden dam was built to generate electricity for Medford in 1904. The sediment was scheduled to be analyzed for its content — including for mercury or other contaminants — sometime next year.

"Given what's been found at other areas like Savage Rapids (Dam), we don't expect there to be any contaminants," Bernhardt said. "But we'll wait and see."

Those results will be key to determining which environmental studies will be needed for eventual design demolition bids, which could be submitted as early as 2011, with the actual removal the following year, Bernhardt said.

Once the sediment is flushed out, the remaining bedrock would likely form a steep gradient that county officials hope will create a whitewater playground that attracts a new set of recreators to the Rogue Valley.

"Here we potentially have a really great feature set up for that," Bernhardt said. "We just won't know until the dam is removed."

Already, a wave on the downstream end of the dam's fish ladder is a favorite play-place for kayakers who would love to see some form of rapid or series of rapids to replace it once the dam is gone, said Bill Cross, an Ashland canoeist and rafter who is following the dam's fate.

"They'll be disappointed to see the wave go, but I've never heard any of them say they'd want the dam to stay just to keep the wave," Cross said. "But a lot of them would like to see a replacement for that."

But whether the county or anyone could leverage the permits to artificially create rapids, falls and pools where the reservoir now rests likely is a long shot.

Bernhardt and Cross agree that creating water parks, like those in Colorado, along a stream that is home to federally threatened species such as the Rogue's wild coho salmon likely wouldn't be allowed.

"If any modifications were done, it would have to be completely compatible with endangered species," Bernhardt said.

Still, kayakers' concerns will be part of the heap of factors the county will weigh before ultimately deciding what to do with its dam that stopped functioning as a electrical plant more than 30 years ago.

"We want to be sure we do significant public outreach and make sure any stakeholder issues are addressed," said Steve Mason, a consulting biologist hired by the county to oversee the project.

The upcoming studies and other work by HDR Engineering will cost the county $82,885 and will be paid from a $100,000 Ecotrust grant the county received last summer, Bernhardt said.

The dam is considered one of the 10 worst artificial fish-passage impediments in Oregon, according to the Oregon Department of Fish and Wildlife.

With Savage Rapids Dam set for removal next year and the Gold Hill diversion dam removed last summer, Gold Ray Dam remains the last major impediment between Lost Creek Lake and the Pacific.

Interest in doing something with the aged concrete dam spans the gamut of government agencies and private groups since its decommissioning as a hydroelectric plant in 1972.

The dam's fish ladder at times causes upstream migration blockages, and salmon and steelhead smolts heading downstream can plunge over the dam's 35-foot drop while finning toward the ocean.

The dam creates a thriving wetland for birds and other wildlife, but the impoundment warms Rogue flows and allows for predators to feed on infant salmon and steelhead.

The county, which took ownership of the dam and 29 surrounding acres in 1972 when it earmarked the area for a park, has civil liability for the structure. Since then, the dam has sat rather unceremoniously in the Rogue with no vocal constituency for keeping it.

"Compared to other dams in the area and the state, there's not been much outcry," Mason said.

Still, removal is not a foregone conclusion, Bernhardt said. Notching or buttressing it remains possible, but removal appears the least expensive way to settle the county's liability for it, she said.

Reach reporter Mark Freeman at 776-4470, or e-mail mfreeman@mailtribune.com.