Widening Coal Creek Parkway

Story by Carl Molesworth | September 28, 2010

A two-phase project is widening Coal Creek Parkway in Newcastle, Wash., to improve safety and relieve congestion on the suburban route paralleling Interstate 405 between Renton and Bellevue.

The project will widen one mile of Coal Creek Parkway between SE 84th Way and SE 95th Way/city limits from two lanes to four travel lanes with left-turn pockets, landscaped medians, bike lanes, sidewalks, curb and gutter, crosswalks, illumination, and drainage facilities. Three new traffic signals will be installed at SE 89th Street, May Valley Road, and SE 95th Street. The existing 56-year old May Creek Bridge is being replaced with a four-lane structure, which will have a median barrier system. Pedestrians along most of the one-mile corridor will be separated from traffic by traditional concrete barrier.

With a construction cost of nearly $29 million, this is the largest project that the city of Newcastle (population approximately 10,000) has ever done, said Eric Robinson, city engineer.

"The city has been trying for 13 years to finish this project," Robinson said. "We got a lot of help from a lot of funding partners."

The project actually involves two separate construction contracts. Phase 2 extends from SE 84th Way to SE 91st Street, while Phase 3 covers from SE 91st Street to SE 95th Way and includes the May Creek Bridge. These contracts extend the Phase 1 improvements recently constructed between Newcastle Way and SE 84th Way.

Robinson said the city had several reasons for splitting the project in two phases, even though they are being built simultaneously.

"We decided they are two different disciplines," the engineer explained. "If we broke them up, we would get more bidders and possibly more competitive bids. Also, Phase 3 has federal funding, and Phase 2 doesn't."

The strategy worked, Robinson added, when each phase drew four competitive bids last summer.

CH2M Hill designed both phases of the Coal Creek project and also is serving as construction manager for the city.

One Side at a Time

The city of Newcastle awarded the Phase 2 contract to Marshbank Construction Inc., Lake Stevens, Wash., on a bid of $15.9 million and the Phase 3 contract to C.A. Carey Corp., Issaquah, Wash., at $12.9 million. Work began in September 2007 on Phase 3 and in October on Phase 2.

An interesting aspect of the project is that both of the prime contractors are serving as subcontractors for the other: C.A. Carey is building structural retaining walls on Phase 2, and Marshbank is performing earthwork for Phase 3.

"It's pretty neat," Robinson observed. "It has worked out very well."

In both phases, the sequence of work has been to construct the eastern half of the roadway and bridge over the 2007–08 winter/spring, then shift traffic onto the two new lanes while the contractors build the western half. That way, only minor roadway closures will be needed throughout the project, Robinson said.

The project's design, combined for the two phases, calls for about 68,000 cubic yards of excavation, 18,500 tons of asphalt, 5,300 linear feet of concrete barrier, and 5,500 feet of guardrail, Robinson said. The contractors also are undergrounding all overhead lines, making drainage improvements and landscaping along the route.

The Phase 2 contract covers the project's northern six-tenths of a mile. The work includes straightening a curve in the road and building four retaining walls along the east side. The largest of the walls, No. 104, is 1,280 feet long with a soldier pile section and a soil nail section.

Craig Jackson, construction manager for CH2M Hill on the project, said the contractor saved the owner a considerable amount of money by suggesting the walls be built of carved shotcrete instead of cast concrete panels.

This phase required blasting at the north end near a rock outcropping to excavate and construct the area for the North Stormwater Pond at SE 89th Place. Jackson reported in his project blog that blasting was performed at 11:30 a.m. on March 6. Seventy holes (each up to 11 feet deep) were drilled into the rock. Each hole was packed with 8 pounds of explosive and set off milliseconds apart. Blast blankets were used to eliminate flying rock, and no problems were observed. Traffic on Coal Creek Parkway was stopped for only 10 minutes to accommodate the blasting.

Not Your Average Project

The Phase 3 work area is four-tenths of a mile long with the May Creek Bridge in the middle. The three-span bridge is 290 feet long, with the middle span over the creek longest at 110 feet. Its design features prestessed, precast concrete girders on eight deep, 6-foot-diameter drilled shafts and six 3-foot-diameter drilled shafts.

There was artesian ground water in the earth under the east side of the bridge, requiring the contractor to extend the steel casings above the ground and drill through them to maintain a positive head during drilling, Robinson said.

Concrete Tech, Tacoma, is supplying the bridge girders. Those for the east side of the bridge were installed in mid-February, using two cranes to lift them into position. By March 7, the contractor was working to form and place rebar and then to place concrete in the intermediate diaphragms. These diaphragms act to stiffen the girders. The deck was poured for the east half of the bridge on April 16.

After the first bridge half opens in June, C.A. Carey will demolish the old bridge and construct the other half of the new bridge. A defining feature of the new bridge will be its decorative steel arch frame, 18 feet high, running the length of the span.

So far, the project is on time and on budget, despite delays caused by bad weather during the winter. As might be imagined, traffic control is a big issue on the project, but the safety record has been spotless. Soil conditions have posed another challenge, with about 3,000 cubic yards of unsuitable material requiring removal.

"This is not your average roadway widening project," Robinson observed. "It has a lot of interesting features."

Indeed, not many projects have a mascot, as Coal Creek Parkway does. Jackson reports that a neighborhood rooster has become the unofficial mascot.

"He is very territorial and supervises or surveys all work done on the bridge project," Jackson wrote in his blog. "He can usually be found roaming around somewhere within the project."

The project schedule calls for Phase 3 to be completed in March 2009, and Phase 2 will follow in June 2009. At that point, the only remaining two-lane section of Coal Creek Parkway will be across the city line in Renton, from NE 23rd Street south to State Route 900. The city of Renton let a contract this spring to widen this roadway to five lanes. That project will be done in conjunction with improvements within the King County portion of the road and should take about one year to complete.