Main work set for June Culvert repair under way

Crews will begin placing 20-foot sections of culvert under Interstate 405 the third week of June to replace a culvert that collapsed in a massive winter storm in December, threatening the stability of the freeway.

By Dean Radford • May 29, 2008 7:26 pm
Workers drilled a pilot hole this week for a four-inch pipe just south of City Hall on Main Avenue that will monitor any ground movement when a 51-inch culvert is replaced in June under Interstate 405.
Workers drilled a pilot hole this week for a four-inch pipe just south of City Hall on Main Avenue that will monitor any ground movement when a 51-inch culvert is replaced in June under Interstate 405.

Crews will begin placing 20-foot sections of culvert under Interstate 405 the third week of June to replace a culvert that collapsed in a massive winter storm in December, threatening the stability of the freeway.

To prepare for that project, workers earlier this week drilled a 320-foot “pilot hole” for a four-inch monitoring pipe about five feet above the new culvert.

The idea is to monitor any movement of the soil, according to project engineer Ty Watterson. The work was easily visible from Main Avenue South, just south of City Hall.

The culvert carrying Thunder Hills Creek under I-405 collapsed on Dec. 3. That old culvert is being filled to prevent any further collapse.

In late December crews working for the state Department of Transportation completed three runs of pipe in a new emergency pumping system to protect I-405 from a heavy rainstorm.

The system activates when creek levels rise and pumps water into the pipeline that carries the creek along the northbound shoulder of I-405, onto Talbot Road underneath I-405 and into a wetland.

The new culvert, 51 inches in diameter, is in essence being pushed through the ground, under I-405, in 20-foot sections. Eventually, it will go under Main Avenue South.

The new culvert is running next to the old one and will extend farther than the existing one to accommodate the widening of I-405, according to Greg Phipps, a state Department of Transportation spokesman.

The work in June will result in some intermittent closures from 9 a.m. to 2 p.m. of Main Avenue South so crews can move equipment and remove dirt, according to Phipps. A flagger will direct traffic.

The work to replace the culvert should finish in July. About $8.5 million is budgeted for the project.

Trees also have been removed from that stretch of Main Avenue and nearby as part of the widening project for Interstate 405. The widening will require that Puget Sound Energy move some of its power lines, according to Craig Kanaya, a spokesman for the state Department of Transportation.

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