A new culvert carrying the Thunder Hills creek underneath Interstate 405 near the Main Street overpass has been installed – months behind schedule but ahead of winter rains.

The work was finished today (Friday) to replace the original culvert that collapsed during record rain storms last winter. Work crews were easily visible from the freeway and from Main Street just south of Renton City Hall.

“As of noon today, the creek was running through a new culvert under I-405,” said project engineer Dave Lindberg Friday in a press release. “We’re very pleased to have the culvert in place before winter gets under way.”

Crews originally expected to finish replacing the culvert by the end of July, but were delayed when the boring machine used to push the steel pipe sections underneath I-405 became stuck. The project team developed a plan to recover the machine by tunneling from the east side of I-405 and work resumed in October.

Crews welded the 20-foot-long sections of steel pipe together to create a continuous, 320-foot-long pipe under the freeway. The new culvert is 51 inches in diameter. Crews will spend the next few weeks removing the pumps and piping that have diverted Thunder Hills Creek during the repair work.

“Taking down the pump system will take a couple of weeks,” said Lindberg. “Drivers can expect some single lane closures overnight as our trucks move equipment from the site.”

In December 2007, record-setting rain damaged sections of a 320-foot-long culvert 45 feet underneath I-405. The collapse created a sinkhole just 12 feet from the southbound shoulder of I-405. Crews stabilized the sinkhole and diverted the creek so they could repair the culvert.

For more information, visit the project Web page: www.wsdot.wa.gov/Projects/I405/RentonCulvertReplacement.