Bridge will stretch over Whychus Creek

The thudding echoes of a pile driver pounding bridge supports into Whychus Creek marked a milestone in Sisters' growth last week. After years of waiting and wrangling, the construction of the bridge that will connect Timber Creek and Creekside subdivisions is now underway.

The construction project is operating in a narrow window of time to insure that there is minimal disruption to the stream bed and downstream spawning grounds. The project will require several different entities to work together to complete the span.

Building a bridge over a stream that is susceptible to flooding and is also undergoing extensive restoration to bring back the fish that have historically made the creek their home is no simple matter.

"An important thing in the bridge design is that it provides enough stream and flood plain width during high flows, and the construction needs to occur before the spawning season for the red band trout," said Michael Riehle, a fish biologist for the Sisters Ranger District.

The construction of the bridge is the responsibility of Bruce Forbes, who agreed to build the span when he was developing the Timber Creek subdivision. Although he sold the development early in the project, Forbes retained the responsibility to construct the bridge.

"The city has nothing to do with the construction of this bridge," said Gary Frazee, Director of Public Works for the City of Sisters.

The developer of the Creekside subdivision is responsible for completing the road and approach apron on the south side of Whychus Creek and the current developer of Timber Creek will build the approach apron and road that will connect to the bridge on the north side of the creek.

"The bridge should be completed in 60 to 90 days," said Forbes.

"The current owner of Phase VI, which abuts the bridge, is Taurus Homes development. As part of the sale to Taurus Homes development for Phase VI of Timber Creek II, I gave them a discount to allow for building the infrastructure. The discount allowed for all the roadwork, bike paths, sewer (and) water mainlines, utilities and associated work to the bridge," said Forbes.

The construction of the bridge is being conducted to minimize the impact on Whychus Creek.

"Our concerns from the fish and wildlife point are relative to two things. We want to make sure that we don't see any constriction of the creek. The span is fairly large, and so they are putting a number of pilings in the creek, but we want there to be as little obstruction in the creek as possible," said Ted Wise of the Oregon Department of Fish and Wildlife.

"We worked with them, and actually they are working outside the recommended work area. But we have worked to give them an exception based on the fact that they will not be working in the water channel, or if they are they will use a mitigation device to prevent damage to the eggs that could have been laid in the gravel," said Wise.

The shock wave from the driving of the pilings, if unmitigated, can damage the eggs by allowing the concussion to shift the gravel or directly damage the eggs.

"We use a very low-tech approach to the mitigation," said Wise. "When the pilings are being driven in water, they are wrapped with a hose that leaks small air bubbles into the surrounding water - sort of a mini jacuzzi. Since water is not compressible and the air bubbles are, the concussion from the pile driving is greatly diminished. We are really working to try to facilitate the construction as much as possible."

Construction costs have escalated and will certainly be far more than was originally anticipated in 2001 when the commitment was initially made to build the bridge; yet, "the final cost of the bridge is not known at this time. I did not post any bond (for the bridge construction)," said Forbes.

According to city officials, some $430,000 was collected in development assessments for the project.

The bridge provides a much needed second route from the area that is experiencing strong development.

"Today there is only one way out of here. My guess is there are probably 200 houses in this area. It will be critical to get a second way out of here. If there were ever a fire or a flood, there just is no other way out," said Frazee.

The city has allowed the access of the bridge to be such that it will be more a of neighborhood access than a thoroughfare. "It was designed with a number of traffic calmers. The bridge does not provide a straight shot (into or out of town). It was really meant to discourage a lot of truck traffic. It was designed to be a local access bridge," said Frazee.