Crews working to restore a 500-foot section of Ashland Creek on either side of the Water Street bridge Wednesday dived into the chilly stream to install pumps that will divert the creek through a pair of large pipes around the project area for about a month.

Crews working to restore a 500-foot section of Ashland Creek on either side of the Water Street bridge Wednesday dived into the chilly stream to install pumps that will divert the creek through a pair of large pipes around the project area for about a month.

Once the creek is diverted, crews will remove an irrigation dam built a few hundred feet downstream from the Water Street bridge and restore the channel to increase its capacity for handling floods and improve fish habitat, contractor Scott English said.

Today, crews are scheduled to suck dry a 300-foot bend in the stream and relocate fish trapped in the area before beginning restoration work, said English, principal restoration biologist for Ashland-based Northwest Biological Consulting.

The company was awarded the $247,452 contract by the city after more than two years of research, planning and analysis of the site, city Project Manager Morgan Wayman said.

In addition to restoring natural vegetation and fish habitat along the creek, the project will ensure the stream's capability of handling a major storm event at the Water Street bridge, Wayman said.

More than 4 feet of sediment has gathered under the bridge since the existing span was constructed in 2005, filling most of the creek's channel and widening the stream to more than 40 feet beneath the bridge, project engineer Russ Lawrence said.

"If a 100-year flood comes, this bridge is not going to pass it in its present shape," he said. "The sediment is accumulating, and the dam is the underlying cause."

The water is less than a foot deep beneath the bridge, where it should be several feet deep with a channel width of no more than 15 feet, he said.

"A major part of this project is to increase the stream's depth "… and stream power," Lawrence said. "Its ability to move the water."

Crews will remove tons of sediment from where it has backed up behind the dam, built in the 1800s, and reconstruct portions of the creek bank, he said. A half-dozen horseshoe-shaped barriers made of river rock and rootwads will be constructed in the area. As water flows over a barrier, it will spill onto the creek bed and form a natural pool, improving stream capacity and fish habitat, he said.

After the project, the stream will be about 40 percent deeper, and its downward grade will be increased by about 2 percent in the project area, Lawrence said.

Water Street between B Street and Central Avenue will be closed for most of August, Wayman said. Pedestrian walkways will be closed from 9 a.m. to 6 p.m. during workdays and reopened on weekends. There will be access to all residences and businesses within the closure zone, he said.

Northwest Biological Consulting has until Sept. 15 to complete the project.

The Oregon Department of Fish and Wildlife will take part in the fish recovery process today, Wayman said, and keep a close eye on the stream as it is being diverted.

"There are a lot of eyes on this project, because it is a very important one," Wayman said. "It's a naturalization and beautification of the stream back to presettlement conditions "… a lot of it is focused on improving the hydraulics of the stream."

Crews also will place heavy logs in the stream and remove evasive plants along the creek's banks and replant with alder, willow, cottonwood, Oregon white ash, snowberry and other native species, English said.

A few of the about 12 rootwads the crews will use to make the barriers will come from conifers removed inside the project area, Lawrence said.

Pumps capable of diverting 3,000 gallons of water per minute around the project area will start a monthlong spree of work this morning, sucking from a pool created behind the crews' temporary coffer dam, English said.

The affected fish, mostly rainbow trout, will be relocated using buckets and nets, he said.

Reach reporter Sam Wheeler at 541-499-1470 or email swheeler@dailytidings.com.