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September 19, 2016

Repaving Tacoma bridges was delicate job for Tucci

By BENJAMIN MINNICK
Journal Construction Editor

Photo from Tucci & Sons [enlarge]
Smaller machinery and lighter trucks were used to keep weight down on the older bridge.

Traffic lanes on the Tacoma Narrows bridges have a tough life.

First, they take punishment from about 40,000 vehicles a day. Then there's a fierce marine environment beneath the bridges and, finally, freeze-thaw cycles take a toll every winter. On top of all that, asphalt lanes on the older bridge are only about a half-inch thick to keep the weight down.

WSDOT says the bridges had not been repaved since 2007, and needed a new surface. The total cost was $1.5 million.

Tucci & Sons of Tacoma finished the job last week for WSDOT.

Tucci project manager Jeremy Hopson said crews had to comply with strict tolerances while removing the old asphalt. He said a micro milling machine was used to grind off old asphalt and 4,000 feet of old conveyor belt material was laid over the bridge grates to keep material from falling into the water below.

Reece Construction Co. of Marysville did the grinding.

The grinding machine could only get within about 1.5 feet of each of the bridges' 45 transverse joints, requiring crews to carefully jackhammer the remaining asphalt around the joints.

“It's about as technical of a paving job as you can have,” Hopson said.

Work on the newer bridge was done on weeknights, and crews immediately laid asphalt on the freshly ground surface.

The older bridge was closed over two weekends so crews could do the work. Hopson said that span has a narrower work zone and can't handle as much weight, so traffic was kept off, and smaller machinery and lighter dump trucks were used.

Hopson said the existing asphalt on the older bridge was in good shape although it was worn, but the surface of the newer bridge was in worse condition.

Jon Keeth, assistant project engineer in WSDOT's Tacoma Project Engineer Office, said the older bridge has a 5/8-inch-thick asphalt deck over a concrete base. He said it was delaminating in places and potholes were forming, but that's typical for that type of system.

Keeth said the newer bridge has a 2-inch-thick asphalt deck over a metal base. He said the asphalt was breaking down and aggregate was coming loose, requiring WSDOT crews to periodically repair some sections. About 1.25 inches were stripped off and replaced to create the new deck.

Keeth said the new decks should last about 10 years.

WSDOT expects to have maintenance crews out tonight and tomorrow night to repair joints on the older bridge. That will require closing two lanes each night.

Tucci's team will come back in the first week of October to stripe the lanes.


 


Benjamin Minnick can be reached by email or by phone at (206) 622-8272.




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