MARYSVILLE — What goes up must come down. For the nearly 60-year-old State Route 529 Snohomish River Bridge between Marysville and Everett, it’s the drawspan that must go up and come down reliably and safely.

To ensure that continues for many years to come, contractors for the Washington State Department of Transportation are gearing up to get down to work, replacing heavy pieces of machinery that operate the southbound drawspan.

“Replacing this machinery is vital infrastructure work,” WSDOT Project Engineer Mark Sawyer said. “We need to keep the bridge drawspan in good working condition for the thousands of travelers who cross it every day, and the vessels that carry millions of dollars worth of goods under it every year.”

Beginning Sunday, Sept. 8, drivers traveling between Marysville and Everett will need to use Interstate 5, while the southbound lanes of SR 529 are closed from 8 p.m. until 4 a.m. on Sunday through Thursday nights. The drawspan will not open for marine traffic during the highway closures. Drivers will also experience up to two weekend closures before this $3.2 million project is complete in October.

PCL Civil Constructors will replace four steel axles, wheels and dozens of counterweight cables that operate the lift span. These lift mechanisms are showing signs of wear and fatigue, including cracks, after years of hoisting and lowering a combined 250 tons of counterweight with each drawspan opening, with about 600 openings each year.

Crews will use a heavy-load crane to remove the old machinery and lift the new pieces into place. The drawspan machinery is housed in two towers 80 feet above the southbound lanes. The northbound drawspan underwent similar repairs in 2006.