Crew samples Deschutes floor

Bore test aimed at finding firm footing for new Colorado bridge

By Dylan J. Darling / The Bulletin / @DylanJDarling

Published Nov 14, 2013 at 04:00AM

A drill crew bored into the bed of the Deschutes River at Colorado Avenue this week to see how far down the bedrock lies.

The drilling was part of an investigation of the ground for the Bend Park & Recreation District, which plans a new footbridge over the river near where the current bridge parallels the Colorado Avenue Bridge.

“We are looking for intact, competent bedrock,” said Shane Cochran, staff geologist with the Wallace Group, a Bend-based environmental engineering firm. A crew from Cascade Drilling out of Portland did the drilling.

They found basalt bedrock 40-50 feet below the river bottom. Cochran said the company will put rock samples through compression tests at a laboratory, which will help tell the park district what type of foundation it should use for the bridge and how deep into the ground it should extend.

“We can base the design on the material underground,” he said.

Bridge construction is set to be part of the installation of safe passage over the Colorado Avenue Dam for boaters and floaters. The $7 million-plus safe-passage project was among the list of park upgrades around town to be partially funded by a $29 million parks bond that voters approved in November 2012.

Earlier this year, the park district chose to place the new bridge just upstream of the current footbridge after gauging public preference.

“It is very close to where the current bridge is,” said Chelsea Schnider, project manager for the park district.

Members of the public disliked an alternative spot for the new bridge, located downstream by about 100 yards. Concerns about placement ranged from harming views from McKay and Miller's Landing parks along the river to enticing people to jump from the bridge into the water.

The park district also looked at the design of the bridge itself and is opting for a 12-foot-wide, 310-foot-long span with a 16-foot-wide viewing platform in the middle. The current footbridge is 24 feet wide. The platform on the new bridge is intended to allow spectators to gather and watch boaters and surfers in a whitewater play area planned for just downstream of the dam.

Schnider said construction of the bridge should start next summer, and the goal is to have it done by June 2015.

The Bend Paddle Trail Alliance, a nonprofit, has committed to raising $900,000 to help cover the cost of the safe passage project. The group hopes to have the total amount collected by the end of next year, said Jayson Bowerman, a Bend Paddle Trail Alliance board member.

“We are over halfway at this point,” he said.

The group is also looking for anyone interested in donating basalt boulders, which would be used in building the whitewater play area.