The Building Tradesman Newspaper

Friday, January 24, 2020

On the Mackinac Bridge... Scaffold system recognized for giving painters safe place to work

By Marty Mulcahy, Editor

ST. IGNACE - In the depths of a Michigan winter, let's think warm-weather thoughts about our state's most recognizable symbol - and it's greatest engineering masterpiece.

Last year the project to remove original 1957 paint from the Mackinac Bridge towers and apply a new coating was recognized by Structural Engineers Association of Illinois for the one-of-a-kind pieces of equipment and creative thinking that went into the scaffold and encapsulation process.

"Industrial painting requires some pretty advanced equipment, from removal and collection to providing working conditions safe from wind and rain," said the Mackinac Bridge Authority. "Add to that the challenge of performing that work on the 552-foot towers of the Mackinac Bridge, and some creative engineering is required. The movable scaffold system designed by Ruby+Associates of Bingham Farms, Mich., fabricated by Moran Iron Works of Onaway, Mich., and used by Seaway Painting of Livonia, Mich., not only allowed that job to be done efficiently on both towers of the bridge, but also earned a structural engineering award in competition with many other impressive projects."

Last year at the Structural Engineers Association of Illinois 2019 Excellence in Structural Engineering Annual Awards, Ruby+Associates took home the Best Neighboring State Project Award for the design of the bridge painting platforms. Safely using those platforms over the past two years have been Painters District Council 1M union members employed by Seaway. 

“As this is the first time in the bridge’s history when the towers have been stripped to bare metal and repainted, it makes sense that Ruby+Associates, Moran Iron Works, and Seaway Painting would need new, innovative equipment to get the job done,” said Mackinac Bridge Authority Executive Secretary Kim Nowack. “We congratulate them on the award and thank them for their work preserving this infrastructure icon.”

The platforms were custom designed and built for Seaway Painting crews to enclose and move up and down the bridge’s towers above the roadway deck, first during the 2017-2018 project to strip and repaint the bridge’s North Tower, then again during the current 2019-2020 project to do the same on the South Tower. The platforms encircled the tower legs and allowed workers to adjust it to accommodate the towers' tapering near the top. Another platform allowed access to the struts joining the tower legs.

The scaffolding system earned the project a write-up in the November 2019 issue of Civil Engineering. "For maximum schedule efficiency," the article said, "the system needed to be enclosed so that workers could sandblast and paint a complete section during the course of one shift. After an iterative design process, the result was a two-story, lightweight, movable steel and aluminum platform system that can encircle the individual legs of the tower. Canvas walls ensure that all debris can be gathered and work can be completed in winds of up 60 mph."

"After extensive research early in the project, it dawned on us that these were first-of-a-kind platforms we were designing and detailing without any examples or guidance,’' said Myles Badour, PE, a project engineer for Ruby-Associates, as quoted in the article.

The award nomination noted that the enclosure needed to capture 100 percent of the paint as it is removed, and it was then shipped to an appropriate landfill facility. The new paint, which is zinc-based, is expected to last at least 35 years, with periodic maintenance.

The South Tower contract is for just less than $6.5 million, with Seaway required to complete the project by Dec. 31, 2020. The contract to repaint the North Tower was just less than $6.3 million. Installation and removal of the platforms required brief closures of the Mighty Mac during the overnight and early morning hours on several occasions.

SEAWAY PAINTING and members of Painters District Council 1-Michigan raise a uniquely designed, and award-winning painting platform on the Mackinac Bridge’s North Tower. Davit-like “outriggers” at the top of the towers support the platforms.

A PAINTING PLATFORM and canvas enclosure , near the top of one of the 552-tall Mackinac Bridge main towers, allows for the contained sandblasting of the original paint, and application of new paint in a specific area during a single shift by Painters District Council 1M members employed by Seaway Painting. Photo credits: Mackinac Bridge Authority/Michigan Dept. of Transportation