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Developer Uses Goats to Clear Prickly Scrub from Property for Bridge Project

Posted by Rodney W. Campbell, Guest Contributor

Nov 11, 2016 11:50:32 AM

The goats, which are available for rent, work for months at a time for a very low rate: free range food and modest shelter.

Sellwood-goats-greenbuildermedia.jpgA few dozen Slayden/Sundt subcontractors at the Sellwood Bridge project in Portland, Oregon, had horns, hooves and a healthy appetite for brush. They preferred night work, took daily power naps and never requested time off.

That’s because they were goats. No kidding.

The project, performed for Multnomah County, involved reconstructing the 2,000-foot-long, aging bridge over the Willamette River. When it bridge opened in 1925, Sellwood Bridge was a welcome upgrade from a ferry service that shuttled passengers across the river. The old Sellwood was the busiest two-lane bridge in Oregon, with an average daily traffic count of 30,000 vehicles.

The 60 goats chewed up brush on the site, a green initiative undertaken by the joint venture to eliminate waste generated by humans thinning the thicket by hand. The City of Portland asked the team to clear the trail on the east side of the Willamette River on the $228 million project. The lively livestock spent a couple of weeks onsite in October and are returning in the spring to chomp on blackberry vines.

The animals are owned by Goat Power, a husband and wife who travel the Willamette Valley with their four-legged friends in a refurbished bus. The goats go from one job to the next, working months at a time.

The project team was committed to sustainable measures from the beginning:

*The bridge was constructed in accordance with the Greenroads sustainability rating system for transportation projects, including LED bulbs in the luminaires, separate pedestrian and bike signals at intersections, addition of two water-treatment swales, improvement of existing nature trails frequented by cyclists and pedestrians and all local/native plants, trees and seeds for landscaping.

*Pilings were removed during an in-water work window of July 10 to Oct. 15 so salmon swimming through the Willamette River wouldn’t be disturbed.

*The truss was taken down in nine pieces and floated downriver to be processed and sold on the open market as scrap commodity for the production of new steel. The four main sections, measuring 200 feet apiece, were lowered onto a barge using four 250-ton strand jacks. Each took approximately a week to remove.

Remaining smaller sections above each temporary bent were hoisted onto a barge using a derrick crane. Once the shoofly truss and substructure were dismantled, a marine subcontractor removed the 80-pipe pile from the river.

*The arches are made of weathering steel. While the mechanical properties are similar to other structural steels, weathering steel has a unique alloy content that causes it to form a durable oxide coating (rust). The oxide film that forms on the surface of the steel is very dense, and after the rust fully matures, it becomes more impervious to further corrosion.

After the steel was installed on the bridge, it quickly developed a bright orange rust, which gradually became a deep brown. The rust serves as a protective coating for the structure.Left unprotected, conventional steel is slowly destroyed by the natural oxidation process and a common method of protecting the steel is to use paint. Using weathering steel eliminates the need for a protective paint system.

For more information, contact the author at rwcampbell@sundt.com.

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