Preliminary results of a new survey of the structure show that all but less than 15 percent of the 350 acres informally called wetlands actually do not contain the plant, soil and water features needed to qualify legally as a wetland, researchers said.

The vast majority of upstream habitat in and around the Rogue River backwaters of Gold Ray Dam appear not to qualify as wetland habitat, possibly making removal of the 105-year-old dam cheaper for Jackson County.

Preliminary results of a new survey of the structure show that all but less than 15 percent of the 350 acres informally called wetlands actually do not contain the plant, soil and water features needed to qualify legally as a wetland, researchers said.

The upstream lands instead appear to be dominated by "upland" habitat, according to preliminary results of the survey that is part of the current environmental study that could lead to the dam's removal.

Should Jackson County, which owns the dam, remove it as proposed next year, the county would have to somehow make up for any lost wetland habitat as required by state and federal laws.

But upland habitat does not require this so-called "mitigation," potentially removing an environmental and financial impediment to removing the structure and restoring 157 miles of free-flowing Rogue, county officials said Thursday.

"If the goal is to remove the dam, this is very good for the project," said John Vial, the county's Roads and Parks Department director.

The findings were unveiled Thursday before more than 100 people during an open house-style meeting called to gather public comments on the proposal.

The preliminary inventory was done by HDR Engineering, a subcontractor working on ongoing environmental studies about the impacts of removing the decommissioned hydroelectric dam deeded to the county in 1972.

Slayden Construction Group has a $5.5 million bid to design a dam-removal strategy, study its potential impacts and remove the dam if the Jackson County Board of Commissioners deem removal is the best way for the county to settle its potential financial liability for it.

Wetland findings will be part of an Environmental Assessment that Slayden must complete before the dam can be removed. If removed, the work must be completed by the end of October 2010 because $5 million of the money comes from a federal stimulus grant that sunsets next year.

Though preliminary, the wetlands finding is the newest shoe to drop on the ongoing study of the dam's impact on the Rogue's environment.

Leandra Cleveland, an HDR wetlands specialist, surveyed the area and found that most of the habitat did not meet the three requirements for what is legally called "jurisdictional wetlands."

To be a wetland, the habitat must have sedges and other wetland plants, have specific soil types and specific requirements for water availability, especially during the growing season, said Scott Wright from the firm River Design Group, which is doing the Environmental Assessment.

"If you're missing one of those three, it's essentially not a wetland," Wright said.

In the Gold Ray case, the vast majority of the acreage had plant species — primarily blackberries — that are not associated with true wetlands, Wright said.

The wetlands inventory has not been finalized and any findings must be accepted by the state Department of State Lands and the U.S. Army Corps of Engineers, which has jurisdiction over wetlands, Vial said.

Under state and federal laws, wetlands lost from projects like this must be replaced either by creating enough wetlands on-site to create no net loss of habitat or by other means.

Other options include building or restoring wetlands elsewhere in the drainage or buying into a wetland "bank" to fund one or more larger wetland projects elsewhere.

Vial said county officials expect some mitigation to be necessary if the dam is removed.

"If we can mitigate on-site, that would be our priority," Vial said.

The environmental and financial impact of losing Gold Ray wetlands was one of two environmental unknowns county officials faced when judging the feasibility of removing the dam and its antiquated fish ladder.

The other was the types of sediment upstream of the dam and whether it contained any contaminants that would have to be physically removed before the dam was breached.

A separate draft study done this summer revealed no dangerous levels of contaminants, including mercury.

That study is under review by state and federal agencies, Wright said.

"There were several things in the project that were huge and we weren't sure they would be overcome," Vial said. "This is the second thing that, basically, has been very positive toward dam removal."

Reach Mail Tribune reporter Mark Freeman at 776-4470 or mfreeman@mailtribune.com.