First elevated train gets fresh coat of paint

Chicago’s Green Line, the elevated train platform running for 22 miles through Chicago’s South Side to downtown, was the nation’s first elevated train. Portions of the line were built more than 100 years ago, and the West Side portion of the line, on Lake Street, featured the world’s first electrically operated rapid transit, put into operation in 1895. Since that time, thousands of commuters have come to rely on the trains daily. But time has taken its toll aesthetically so, the Green Line is being painted for the first time in 40 years.

The refurbishment of the Green Line is part of the $300-million, publicly funded Urban Mass Transportation Rehabilitation Project for the Chicago Transit Authority (CTA), being implemented under the coordination of the city’s Department of Transportation, the Northern Illinois Regional Commuter Railroad Authority, Chicago & Northwestern Railway Company and Beltway of Chicago. Thirty-five million dollars of the money is earmarked for painting.

CTA-specified protective coatings and procedures for painting the structure are based largely on the results of a survey conducted by a team of corrosion and industrial maintenance painting experts. Conducted to determine the state of the existing metal and performance requirements, the survey found that, while some surface rust was present, the structural steel was in surprisingly good condition considering the age of the latticed columns and beams that comprise the platform.

However, the project was complicated by the fact that lead-based coatings had been used years earlier, requiring the use of lead-containment procedures during surface preparation and making the job one of the nation’s largest lead-abatement projects ever. Also, the elevated platform is located on a major roadway crowded with traffic, so the containment systems had to be designed that minimized interference with traffic flow.

Weather conditions, too, affected the specifications. Temperatures in Chicago during the spring and fall — when much of the painting had to be scheduled — often drop below 50[degrees] F, so coatings were required that could be applied in low temperatures.

The system used was comprised of Epoxy Mastic Aluminum II and Corothane II Polyurethane from Sherwin-Williams, chosen largely for the ability to provide a high-build, long-lasting, high-performance protective film for SP-6 commercially sandblasted surfaces. The primer is a high-solids aluminum-filled epoxy coating, offering good adhesion over sandblasted steel and provides a chemical and moisture barrier. The low VOC coating gives painters greater freedom to work around weather conditions. Specifications called for the coating to be applied in a single coat to achieve a total of seven mils DFT. The topcoat is a two-component aliphatic acrylic modified polyurethane that provides a high-build satin finish and offers touch-ups without additional surface preparation. It was specified for application at two mils DFT.

The major portion of the project began in early 1994, when tracks and railroad ties were removed from the line, clearing the way for the supporting steel structure to undergo maintenance painting and repair.

Contractors submitted plans showing the arrangement and type of material to be used for the containment, the size of the containment, the location of a negative air machine and procedures for the collection and storage of the blasting debris.

They were required to hire a U. S. Environmental Protection Agency certified independent air monitoring laboratory to perform personnel air monitoring and environmental monitoring.

Although the width of the structure remains constant at 38 feet in the section being painted, the height of the platform varies from 25 feet to 45 feet, making it difficult to provide containment. The solution to this problem called for six mobile, prefabricated aluminum canopy structures for containment of 100-feet to 120-feet long. Each structure is designed to be water tight and to keep humidity out. Once erected, the structures can remain up for 50 bents to 70 bents, depending on obstacles.

Faced with a variety of obstacles, the painting contractors came up with several solutions. For example, coal slag is used to remove the existing paint on the structure. To paint in very tight areas around the lattice columns that are sometimes considered inaccessible, the contractors use 45[degrees] nozzles with conventional spray equipment.

Additionally, a central site has been set up for staging the project. Equipment for the job is staged at the fixed site, and employees start and end the day there, returning to the decontamination trailer nearby to shower after leaving soiled and potentially contaminated clothing on the site for proper disposal. Each contractor expects to be completed with the Green Line project by July 1995, before the October deadline.