JACKSONVILLE — State dam safety engineer Keith Mills is happy the city is moving forward with plans to breach the Jacksonville Reservoir dam, one of five in Oregon that is rated unsatisfactory.
"At some point this dam, in a really nasty storm, would not survive. This is a real huge priority for renewal," said Mills. "The sediment that is here would be really nasty stuff in a flood."
Under rainy skies Tuesday afternoon, Mills and 19 others gathered at the dam for a discussion on how the project might proceed. Those attending included City Council members, city staff, consultants, Jackson County staff, representatives from the state departments of Environmental Quality and Fish and Wildlife, plus the U.S. Army Corps of Engineers.
People and property below the dam on Jackson Creek would be at peril if the dam failed, said Mills, while fine sediments, much of it decomposed granite, and lots of silt would impact fish-spawning gravel beds in Bear Creek and the Rogue River.
Use of the reservoir, built in 1912, was discontinued in the 1950s when the city obtained water from the Medford Water Commission. Since then, much of the reservoir has filled in. Rough estimates say it may contain as much as 100,000 cubic yards of sediment. The reservoir is about 20 to 25 feet deep.
Breaching of the dam and rehabilitation of the creek to near natural conditions, the city's preference, will need approvals from a variety of agencies and a permit from the Corps of Engineers to perform the work.
Everyone agreed the process will require detailed studies, money and time. Another challenge will be figuring out how to make sure sediments along a restored creek path don't get washed away in a flood.
Jacksonville has budgeted $50,000 to cover engineering expenses and another $150,000 toward notching. The money was part of $680,000 the city received from the Motorcycle Riders Association, along with a 40-acre parcel with an improved parking lot next to Forest Park, in exchange for 380 acres higher in the watershed adjacent to land the group already owned.
Army Corps project manager Joe Sheahan, a biologist, said he doesn't want the sediment moved off the site by nature.
"Looking at it, it would seem fairly mobile," Sheahan said.
Councilman Criss Garcia and others asked about the presence of toxic materials, including mercury from past mining done in the area. No studies have been conducted, he was told.
Northwest Biological Consulting, an Ashland firm that has been involved with dam notching and removal throughout the West, has been retained by the city to prepare a permit application for breaching the dam.
A first step, Sheahan indicated, is to work with his agency to determine what type of soil core samples the company would like to see.
Sheahan suggested the city prepare a couple of possible plans so the Corps could review those possibilities before additional money is spent.
"You don't have enough money to go through two or three engineering studies," said Sheahan.
A quarry where rock was mined for the dam's construction sits just across Reservoir Road from the dam. Refilling that site with some of the sediment was one suggestion offered.
Mills said securing a grant for the work from a government agency is unlikely. Oregon Watershed Enhancement grants are targeted toward fish-passage projects.
Grants from private organizations that promote restoring fisheries or providing clean water might be available, said Scott English of Northwest Biological Consulting. Restoration of a historic steelhead run in the creek might be possible, he said.
Engineering studies to bring the failing dam spillway up to standards showed an estimated price of $500,000. After hearing the price, the City Council voted to pursue notching. Under flood conditions the spillway would not be sufficient to release water coming into the reservoir.
Tony Boom is a freelance writer living in Ashland. Reach him at firstname.lastname@example.org.