Work came to a halt recently to replace a collapsed culvert under Interstate 405 when a boring machine in essence jack-knifed 60 to 70 feet under the freeway.

The delay and the cost to get the project moving again could add between $1 million and $2 million to the $3.7 million authorized for construction.

Those extra costs could come from an emergency fund provided by the federal government as a result of the Dec. 3 storms that led to the collapse of the culvert that carries Thunder Hills creek under the freeway.

Also, the contractor, Tri-State Construction, could bear some responsibility for the extra costs, according to Greg Phipps, a spokesman for the state Department of Transportation.

The transportation department had hoped to have the culvert replaced relatively soon. Now, the completion date is more likely late in August, if not later, according to Phipps.

The state and Tri-State are trying to figure out what happened and then how to get the machine going straight again.

According the Phipps, the freeway was built on fill, rather than solid ground, and the boring machine tends to take the “path of least resistance.”

The stability of the freeway isn’t threatened, nor should motorists on the freeway experience any delays, Phipps said.

The machine is boring a new pathway for the new culvert and at the same time pulling behind it the casings for the new culvert, according to Phipps.

The pumping system that carries the creek’s water through pipes around the broken culvert remains in place. It can handle any major storms that would occur into the fall, Phipps said.

However, it costs about $320,000 a month to keep the pumping system operating, a cost that was only budgeted through the end of July, Phipps said.

Dean A. Radford can be reached at 425-255-3484, ext. 5050, or at dean.radford@rentonreporter.com.