Wood trestle on SR 107 bridge making way for stronger concrete supports

The 200 or so timber pilings that have held up the south approach to the state Route 107 Chehalis River Bridge south of Montesano for decades are being replaced with concrete pillars, the largest ones encased by 2-inch thick steel shafts as the 60-year-old bridge gets a long-awaited structural makeover.

Crews from Rognlin’s Inc. were awarded the contract Feb. 1 for the $23.7 million project, which will include the replacement of all bridge railings, a new paint job, a completely resurfaced roadway and a raised portal on the south end.

The construction was expected to close the bridge today until about 8 a.m. Friday so Washington State Department of Transportation crews can stabilize the south end of the approach because of settlement issues.

Project engineer John Romero said the end result of the project will be similar to the Wildcat Creek bridges on state Route 8 near McCleary, which were recently replaced as part of the state’s fish passage barrier program.

As the east half of the bridge is being demolished, drivers use the western lane of the bridge (which looks like it has been cut in half the long way), WSDOT spokeswoman Christina Werner said. A view from the south approach shows the exposed timber pilings on the east side of the bridge that will be removed.

In the spring, one-way traffic will be shifted to the eastern side of the bridge, as the process is repeated in reverse and the western lane will be constructed.

“The Department of Transportation uses this technique quite often when rehabilitating and building new bridges or structures across the state,” Werner said. “We do everything we can to keep traffic moving while building an entire new structure that meets current seismic requirements and lasts for decades to come.”

Traffic across the bridge is controlled by a signal light at each end. The timing of the light has been tweaked some since it was installed in May to minimize the wait times on drivers and is monitored for safety.

Construction is expected in fall 2020, when the entire crossing will reopen with a single lane in each direction.

A DETAILED PROCESS

The existing south approach of the bridge is held up by the trestle, its wooden timbers set about 45 feet deep. The new concrete shafts, while fewer in number by far, are much more modern and set far deeper.

Two shafts will be 8 feet in diameter and will be set 71 feet deep. Then there are the big ones, eight 10-foot diameter shafts that will be set 95 to 140 feet deep. There also will be two 6-foot diameter shafts set 45-50 feet deep.

The 8- and 10-foot shaft casings are 2-inch thick steel tubes. They are brought out to the site in 40-foot pieces, each weighing about 100,000 pounds, Romero said. A 40-foot section is set in its specific spot and driven into the ground using an oscillator, while a large clamshell shovel excavates the soil out of the tube. Once the tube is in the ground, a second section is placed on top and the two are welded together. It takes four welders 16-18 hours to complete the welding of each section.

The tube is further pushed into the ground with additional sections — four in total with three welds for the deepest — added as needed.

Water from the Chehalis River is put into the shaft when wet soil is encountered. Romero said this is done to help stabilize the hole until the concrete is placed. Once the steel tube is down to the correct depth, a rebar cage, which is built on site, is lifted and placed into the steel tube and left hanging from the crane 6 inches from the bottom of the shaft.

The day after placing the rebar cage, concrete is poured into the shaft. As the concrete is poured in, the water in the shaft is pumped out and stored on site in 10 baker tanks — the blue tanks visible on the east side of the construction site. Once the concrete is poured to the top of the shaft and all the water removed, the contractor repeats the process for the other shafts.

To place a section of steel tube and do the welding connection takes about a day: four sections of tubes takes three days. It takes another day to place the rebar cage; one was set in one of the 10-foot shafts July 18. It takes another day to pour the concrete. All told it takes about a week to set one shaft.

The concrete in the shaft must cure for 96 hours before the shaft can be tested, Romero said. Work cannot occur by the shaft until the concrete reaches a compressive strength minimum of 2,000 pounds per square inch, because vibrations could disturb it.

“It’s a very detailed process. It takes time to do it right,” Romero said.

Rognlin’s had to obtain environmental permits to pump the water from the Chehalis. Since the water will come into contact with concrete during its construction use, it has to be treated prior to being released into the ground. The primary test is the acidity or alkalinity level of the water; water in contact with concrete can become basic and have a pH of 10-11. For the water to be released, it must have a pH of between 6.5 and 8.5. The most commonly used practice to lower the pH is the use of dry ice. Once the water is tested and is shown to be in the right pH range, it must be released into an area that is at least 100 feet away from surface waters, including rivers, creeks, lakes and wetlands.

In the end there will be a new 713-foot concrete structure, Romero said. There will be 36 concrete girders, total length 4,140 feet. The existing bridge railing will be replaced with 2,670 linear feet of brand new railing. And the portal curve, the arch over the roadway as you enter the south approach of the bridge, will be raised by up to 2 feet.

The existing lead paint on the steel truss structure will be removed and the bridge will be repainted. During the removal, a containment system — think of a big tent, Romero said — is used to contain the old paint. The system includes a ventilation filter system to capture the smaller particles and provide clean air to the workers and inspectors. The system catches the removed material, which is vacuumed up and removed from the site. The lead paint material is then hauled away and disposed of at an appropriate facility designed to handle such materials.

The containment system stays in place as new nonlead paint is applied to the bridge and will stay in place until all the cleaned and painted surfaces have been inspected and approved by the Department of Transportation project engineering office. The containment system is inspected daily to verify that it is functioning properly.

Some of the work, like the concrete deck, paving, painting and striping, is weather-related and could be delayed by rain. Still, the project is slated for completion in fall 2020.

A rebar cage is lowered into one of eight 10-foot diameter steel shafts on the west side of the State Route 107 bridge south of Montesano.

DAN HAMMOCK | GRAYS HARBOR NEWS GROUP Christina Werner, State Department of Transportation Olympic Region, stands inside one of the 10-foot-diameter shafts that will be filled with concrete to support the south approach of the State Route 107 Chehalis River bridge south of Montesano.

Photos by DAN HAMMOCK | GRAYS HARBOR NEWS GROUP Two cranes work the west side of the State Route 107 Chehalis River bridge south of Montesano. A crew from Rognlin’s Inc. was awarded the contract for the $23 million-plus project to replace the south approach and other upgrades to the bridge.