Twin Bridges

Story by Carl Molesworth | September 28, 2010

Parsons RCI Inc. is building two nearly identical bridges in Port Angeles, WA, this year as the project team works toward completion of the 8th Street Bridges Replacement Project.

The Port Angeles City Council awarded the base bid on the 8th Street Bridges Replacement Project to Parsons RCI, of Sumner, WA, in April 2007. Five bids were opened on March 13, 2007, with Parsons submitting the low responsible base bid of $18.4 million.

The base bid consists of the removal of two existing timber bridges and replacement with 758-foot-long reinforced concrete structures. The bridges will be 34 feet wide, curb to curb (12-foot lanes and 5-foot bike shoulders) with 6.5-foot-wide sidewalks on each side. The base bid included standard Washington State Department of Transportation railing and lighting plus extensive stormwater systems for stream protection, wetland restoration, permanent traffic and temporary detour signals, and related utility relocations.

Two deep ravines cut through Port Angeles west of the downtown area, making 8th Street the only major east-west arterial in the city, said Glenn Cutler, director of public works and utilities. Valley Creek runs through the eastern ravine, and Tumwater Creek shares space with State Route 117 in the other one. As luck would have it, the ravines are very similar in width and depth where 8th Street crosses them.

"What's nice about this — expensive but beneficial — is that both bridges are about 750 feet long, so there were a lot of common elements," Cutler said.

The city first looked at building slant-leg steel structures, Cutler said, but switched the project to a standard WSDOT-spec concrete bridge design when estimates for building the steel bridges came in at $26 million.

Exeltech, based in Lacy, WA, designed the project and is providing construction management services for the city.

Third Generation Bridges

Cutler said the city decided to replace the wooden trestle bridges on 8th Street due to their condition and design. Water had infiltrated members and caused rotting, which forced the city to down-rate the capacity of the bridges to the point that garbage trucks and larger fire trucks couldn't use them. In addition, the bridges were functionally deficient, with narrow traffic lanes and no bike lanes whatsoever, Cutler added.

The existing bridges were not the first ones to span Valley Creek and Tumwater Creek. The first bridges were built in 1913 but started to deteriorate in 1928 due to the heavier loads caused by increased use of automobiles and trucks on them. The state was asked to make evaluations, but multiple delays occurred due to funding and design changes.

Finally the replacement bridges were built in 1936. These bridges, designed by the Washington Emergency Relief Administration and the Public Works Administration, were built at a cost of $67,000 each. The bridges were actually designed twice. It was originally hoped to build the bridges out of concrete, but wood timber construction was much less expensive and became the chosen material. They were constructed with 800,000 board feet of prefabricated creosoted Douglas fir. At the time, it was expected that the timbers would resist decay and termites for about 40 years.

In 1938, citizens petitioned the city council to install sidewalks and fencing for child safety. Those sidewalks and fencing remained in place until the bridges were demolished last year.

A section of the fencing and two bollards have been donated to the Clallam County Historical Society.

Concrete Bridges

Parsons RCI started the project in August 2007 with demolition of the old bridge over Tumwater Creek.

The suggested sequence was to first remove the portion of the deck over the roadway and creek below. Then the six piers from that section came down, followed by the rest of the western half of the bridge. In Stage 2, the eastern half of the deck and the 13 piers supporting it were removed. A similar sequence brought down the second bridge.

Both of the new 8th Street Bridges are supported by eight drilled shafts, two for each of the four center piers. The shafts are 9 feet in diameter and 30 feet to 60 feet deep, consuming an average of approximately 100 cubic yards of concrete each.

The center piers consist of cast-in-place, Class 400 concrete spread footings topped by twin cylindrical columns, also cast in place. The tallest piers measure approximately 100 feet from the footing to the bridge deck, Cutler said.

The last five of the 25 I-girders for the Tumwater Creek Bridge were delivered and set into place on April 9. Each of the reinforced concrete girders weighs approximately 170,000 pounds. They range in length from 138 feet to 155 feet and are 7 feet tall. The girders were manufactured by Concrete Technology Corp. and transported from Tacoma with special heavy-capacity trucks by Van Dyke Inc., of Seattle. Transportation of the girders required coordination with several agencies along the route and special permitting by the Washington State Department of Transportation.

Two crawler cranes were used to set the girders, said Ingo Goller of Exeltech, who is serving as construction manager for the city.

"They did a haul-off for both end spans," Goller explained. "The middle ones were double-picked."

In late May when PB&E visited the project, workers were installing the brackets for the bottom forms of the Tumwater Creek Bridge deck and the overhangs for the sidewalks. A temporary debris deck had been installed on the bridge for that portion over SR 117.

At the Valley Creek Bridge, work continued with the construction of the columns, column caps and pouring of cement. It was anticipated that girders for the Valley Creek Bridge will arrive sometime in June.

Goller was very complimentary of the work that Parsons RCI and its subcontractors are doing. In addition to recording zero loss-time accidents so far on the job, the construction team has been quite sensitive to environmental issues

"Parsons has done a very good job monitoring to make sure we don't get either creek loaded with sediments," Goller said. "Overall, Parsons is a very conscientious contractor."

Cutler said the project is expected to be complete by late fall or early winter of this year. The sequence calls for finishing the Tumwater bridge first and opening it to traffic, then completing the Valley Creek Bridge about eight weeks later.

Lots of Construction

Port Angeles, an attractive waterfront community of about 18,000 people at the top of the Olympic Peninsula, is a beehive of construction activity this year.

Public projects in and around the city valued at upwards of $150 million are either under construction or in the works, Cutler said. Near the waterfront in downtown Port Angeles, Primo Construction is building the International Gateway Project for the city. This $7.4-million building, which consists of a two-level parking garage with a pavilion and clock tower on top, will improve the interface with the two ferries that fun between Port Angeles and Victoria, B.C., Cutler said.

In addition, two water plants are being built to protect the city's water quality when the Elwha River dams are removed in a few years. One is a 51.2-million-gallon surface water initial treatment plant, and the other is an 11-million-gallon drinking water plant.

Clallam County is building a $16-million bridge over the Elwha River as well. And among the private projects spurred by the public construction is a $4-million office building in the downtown area near the water.

"It's a time of great opportunity," Cutler said. "Never in my wildest dreams did I expect to see this much going on at once."