Jacksonville officials are moving forward on plans to breach the Jacksonville Reservoir dam, one of five in Oregon that is rated unsatisfactory.
Beyond just removing the dam, the project must ensure sediment trapped behind the dam doesn't wash down to cause problems elsewhere, officials explained at a meeting this week to kick off the work.
"At some point this dam, in a really nasty storm, would not survive," said Keith Mills, a state dam safety engineer. "This is a real huge priority for renewal. The sediment that is here would be really nasty stuff in a flood."
People and property below the dam on Jackson Creek would be at peril if the dam failed, Mills said. Fine sediment, much of it decomposed granite, and lots of silt would impact fish-spawning gravel beds in both Bear Creek and the Rogue River.
The reservoir was built in 1912, but the city stopped using its water in the 1950s, obtaining water from the Medford Water Commission instead. Since then much of the reservoir has filled in. Rough estimates say there may be as much as 100,000 cubic yards of sediment. Its depth is estimated at 20 to 25 feet.
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.
Jacksonville has budgeted $50,000 to cover engineering expenses and another $150,000 towards notching. The money was part of $680,000 the city received from the Motorcycle Riders Association. The association gave the city the funds and a 40-acre parcel with an improved parking lot next to Forest Park, site of the reservoir, in exchange for 380 acres higher in the watershed adjacent to land the group already owned.
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.
— Tony Boom
Read more in Friday's Mail Tribune.