State Route 900 trail connector hits bump
November 16, 2010
By Warren Kagarise
Unstable soil causes crews to dig deeper
The trail connector under construction at Interstate 90 and state Route 900 hit a bump in the road last month, as crews had to dig deeper to reach a sturdier soil layer to support a series of concrete-and-steel piers.
City engineers said the extra digging is not expected to delay the project. The connector — arranged along almost one-third of a mile from the state Route 900 boardwalk on the south side of the interstate to the Sammamish Trail on the north — should be completed in April.
Crews needed to find a solid surface to support the piers and had to dig 20 feet to 30 feet deeper than initially estimated to find a bearing layer. The snag prompted the Issaquah contractor C. A. Carey Corp. to bring in additional equipment to complete the digging.
“It’s still kind of a concern, but they’re continuing to work and we’re working through the issues between us and WSDOT and the contractor,” city Public Works Engineering Director Bob Brock said.
Plans call for the completed connector to feature a 12-foot-wide pedestrian bridge across the westbound interstate on-ramps, plus a 10-foot-wide pedestrian crossing on the existing state Route 900 overpass.
Brock said the contractor had to meet construction standards updated after the 2001 Nisqually earthquake.
“We’re building it to the most current standards, which is causing us to drill down further to get to a little extra bearing,” he said.
City Senior Engineer Rory Cameron said the construction slowdown lasted for about a week in October. The extra feet equaled extra dollars, but engineers said the project had reserve funds built into the budget.
The city awarded the $4.4 million construction contract to C. A. Carey Corp. in June. The total project price tag is about $6 million.
The project relies on grants — including $400,000 from Sound Transit — to offset most of the project cost. The city contributed about $341,000 toward the link. Construction on the project started in July.
Engineers said the project has not faced any serious problems so far and, aside from some traffic backups in the early days, construction has been smooth.
The contract narrowed driving lanes on state Route 900 and closed a high-occupancy vehicle lane to serve as a construction staging area.
In the initial phase, not enough drivers used the center lane on the state Route 900 overpass, causing construction-related traffic backups. The city encouraged drivers to use the center lane to prevent backups and adjusted traffic flow through the corridor.
Warren Kagarise: 392-6434, ext. 234, or firstname.lastname@example.org. Comment at www.issaquahpress.com.