Underground Improvement: Aldridge Electric renovates Chicago subway stations

An electrical worker in safety gear stands on a subway platform under renovation | Aldridge Electric
Aldridge Electric
Published On
Dec 15, 2020

The renovation of three active Chicago Transit Authority subway stations showcases Aldridge Electric’s innovation in transportation infrastructure construction and demonstrates the types of one-of-a-kind solutions Aldridge employs to complete challenging work.

The CTA-owned project focused on the Grand, Chicago and Division stations on the Blue Line along N. Milwaukee Ave. Each station consists of three levels—street entrance, mezzanine and platform, said Jon Lother, Aldridge project manager. Key to timely completion of the project was the re-engineering of a rail cart to drill at exact locations in the side of the subway tunnel wall. The holes accommodated brackets designed to adjust to the changing angles of the mounting surface. The brackets support light fixtures and conduit raceways.

“Aldridge’s scope of work included complete electrical system upgrades of the three stations while keeping all stations open and operational throughout construction,” he said.

Work common to each of the three stations included replacement of normal and reliable utility services at each station, along with new service distribution equipment, such as current transformer cabinets, alternating current-automatic transfer switches, switchboards, inverters and direct current–automatic transfer switches.

Equipment rooms consisted of two existing electrical rooms (one on the mezzanine level and one on the platform level), which were completely upgraded with new equipment while phasing the installation to keep stations operational. A new inverter room was constructed on the platform level.

Work on street-level entrances and mezzanine levels replaced power, lighting and communications infrastructure with phase sequencing of critical fare-collection equipment and electrical operations so that stations could remain active throughout construction.

Limited time to complete lighting replacement on platform levels posed a challenge.

“This work for all three stations was planned and coordinated to be completed during two, 54-hour, single-track outages—the first on outbound tracks, the second on inbound tracks,” Lother said.

“This required a combined effort among our internal divisions for mechanical ingenuity, preparing/loading/staging rail-borne equipment onto the tracks, extensive planning with the use of Aldridge’s agile project planning tools, which consists of work breakdown structure, job-productivity assurance and control, and short-interval scheduling tools and information.

“Additionally, there was the fabrication of components critical to success and actively involved throughout the project led by prefab/BIM program manager, Jeff Buckley. The field execution was completed with safety and quality at the forefront for complete installation of the lighting with minimal impact to operations of the transit system,” Lother said.

Aldridge manager and specialty tooling/custom fabrication expert, Jeff Miller, designed modifications of a rail cart to create a rolling rig to drill anchor arm locations on the side of the tunnel for installation of 15-foot prefabricated lighting brackets.

“The Aldridge fleet department did a great job with platform cart modifications and making all equipment capable and ready to meet the critical timeline,” Lother said.

Mounted on the diesel-powered cart’s flat floor were pneumatic adjustable arms, hoses and collar fittings, a vacuum with HEPA filtration and diesel exhaust scrubber to ensure clean air quality and prevent the displacement of airborne particles throughout the drilling process to meet OSHA silica standards.

“With one operator and the assistance of a three-person platform crew to line up the drills to the proper locations, 10 holes were drilled simultaneously in perfect alignment for the five brackets of each 15-foot section within a 10-minute time frame to stay ahead of the rack installation process,” Lother explained.

“Utilizing the modified cart, other equipment, multiple crews and interdivisional support,” he continued, Aldridge crews successfully performed this work within the very limited time period allocated for it.

“Aldridge’s ability to install the lighting in the two 54-hour periods played a significant role in being awarded the contract for the project,” he said.

The project was completed in nine months.

All personnel who worked on the tracks were required to complete third-rail training conducted by the CTA. Even when power is cut and locked out, workers must go about their jobs as if the rail is energized.

“Aldridge has been providing innovative solutions and successful projects to the CTA for more than 25 years,” Lother said. “We have worked on every CTA line in Chicago.”

Based in Libertyville, Ill., Aldridge Electric has nearly 70 years of experience completing complex and challenging projects in the transportation and power markets while upholding its commitment to being incident- and injury-free.

About the Author

Jeff Griffin

Freelance Writer

Jeff Griffin, a construction and tools writer from Oklahoma City, can be reached at up-front@cox.net.

Stay Informed Join our Newsletter

Having trouble finding time to sit down with the latest issue of
ELECTRICAL CONTRACTOR? Don't worry, we'll come to you.