HDR Aids Reconstruction of Ketchikan Water Street Trestle
A Safer Passage: The Reconstructed Water Street Trestle Benefits Both Local Residents and Tourists in Ketchikan
Adding weather and history components to a construction project complicates matters. These were just some of the complications that were part of the Water Street Trestle #2 reconstruction project in Ketchikan, Alaska. Despite the multitude of challenges, the team persevered and can be proud of their work.
The Water Street Trestle #2 was built in 1979. The trestle bridge was nearing the end of its useful lifespan and was no longer able to support heavy loads. For those residents who live by the trestle, this meant they could not receive deliveries for home heating oil, garbage truck service, nor emergency vehicles should the need arise.
Although the bridge was built just 40 years ago, its timeframe for deterioration is not uncommon. “Timbre supported structures typical life span is 40 to 50 years,” says John Scott of HDR, who served as the Project Manager for the project.
Scott and his team were tasked with inspections, materials testing, and ensuring the contractor built the project to specs. “In a marine environment such as the one where the trestle is located, the salt air takes its toll on a structure which tends to lessen the life span,” says Scott.
While the trestle itself is built along a cliff face, it’s adjacent to the Tongass Narrows, a portion of the Inside Passage,which is a network of waterways and is an offshoot of the Pacific Ocean. Cruise liners regularly travel the area, and Ketchikan is a popular tourist destination. Those tourists who stop in Ketchikan may pass over the trestle as part of a walking tour of the city.
There were a number of construction elements to the project. The work performed included the removal of the old timber and concrete trestle structures and replacing them with a new 700-foot-long, pile supported steel and concrete trestle structure and a new 75-foot-long concrete girder bridge structure.
“The original trestle was replaced by three separate structures: a bridge section, a retaining wall section, and a streel supported trestle,” says Scott. “However, those who cross the trestle would never know there were three different kinds of structures.”
The project also included the construction of reinforced concrete retaining walls and curb and gutter. The concrete sidewalks were built to meet Americans with Disabilities Act specifications, and the new sidewalks replaced ones studded with utility poles. All utilities, sewage, and storm drain systems were replaced. New electrical lines were run to homes, and were buried. The guardrail is designed to take heavy loads and is clad in wood to match the neighborhood.
Minimizing Resident Challenges
The 1,300-foot bridge slopes down dramatically. One side touches the ground while the other is 50 plus feet higher. There are properties at the right of way line at both the uphill side and the downhill side. The width of the area being worked on was approximately 25 feet.
Because of these conditions, the contractor progressed in a very deliberate way. “The contractor moved forward like an inchworm,” says Scott. “They would demolish a section of the roadway and then rebuild it before moving on to the next section.”
Work proceeded this way in order to minimize the access challenges for residents. “There was no through vehicular access, but you could walk through the area,” says Scott. There was a temporary construction easement on either side to allow for the minimal movement.
The uphill side of the trestle is attached to the hillside. Rock nails were used as part of the construction of the new trestle at both the uphill side and at the footings.
“Because of the terrain, a drill rig was suspended by a chain and hoisted to control direction and angle of the rock nails,” says Scott.
Construction of the project commenced in June 2016. It was originally scheduled to be complete by December 31, 2018. However, construction ended in June 2019. “We discovered lots of pockets of deep soil which meant we had to tweak the design,” says Scott.
Those changes included modifications to some of the bridge foundations and changes to the rock nails for the retaining wall. Implementing the changes added time to the project.
Due to the design change, extra time was needed causing the team to miss the paving window. No paving can be done in area between September 15 and May 15 due to weather conditions.
Ketchikan, which is in southern Alaska, is more moderate in temperature than the perceptions many have of Alaska. Although it receives an average of nearly 40 inches of snow per year, the rainfall is what stands out. The average annual rainfall in Ketchikan is between 140 and 160 inches.
There’s a historical component to the project. Water Street, where the work took place, was the main north south route for Ketchikan. As such, lots of fishing vessel captains built their homes there to oversee the marinas and their boats. The homes can trace their history as far back as 1886 when the canneries came to Ketchikan in 1886. As more canneries opened up over the next 50 years, more of the homes were built.
Because of this tie to history, historical elements were tied into the project. A timber rail, which spans the length of the project, was included since it is similar to the early construction of Water Street. In addition, a timber deck located just off the roadway and looks over a gorge area is built in the same style.
The $25 million project, which was funded by the Federal Highway Authority, the Alaska Department of Transportation and Public Facilities, and the City of Ketchikan, is one that Scott is proud of.
“It was a unique and exciting project. I’m proud of the job and believe that everybody involved worked together and faced the various challenges to make it a successful project.”
They have every right to be proud. Building a roadway along a cliff while dealing with challenging conditions is no simple feat. With the completion of the new Water Street Trestle, residents and tourists alike can enjoy safe passage in Ketchikan, beautiful views, and the area’s rich history.