National Park Service
St. Louis, MO

630 FT in Height


Tourist Attraction

Additional Information:
An average of 4 million people visit the Arch each year, up to 6,400 people can use the trams each day.

St. Louis Arch

Gateway Arch, Repair and Upgrade of Controls System, St. Louis, Missouri

This design/build project replaced the aged and obsolete electrical control systems of the Gateway Arch trams with a modern, state-of-the-art, computerized and modular Programmable Logic Controller (PLC) system. The Arch monument and associated trams are one of the primary assets of the Park and the destination point of a majority of Park visitors.  The Tram system and its controls must be maintained at the highest level possible for the safety of park visitors. The existing electrical control system was largely the original hardware in service for more than 40 years, and was difficult to obtain replacement parts.

The new Programmable Logic Controller system improved the Tram system dependability and reduced maintenance, repair, and inspection troubleshooting time with real time on-board diagnostics and remote monitoring available at several locations in the building. The new PLC system is scalable for future electrical infrastructure upgrades and can also be programmed to meet future National Park Service and visitor needs.

The new control system for the Arch Trams utilizes redundant Programmable Logic Controllers (PLC’s), Remote Input/Output (I/O) to monitor operational and safety parameters through the Tram system, touch-screen Human Machine Interface (HMI) operator stations, wireless communications between the Trams and the control systems, a fiber optic communications trunk and a PC-based programming terminal.

In conjunction with the installation of the new PLC system, the team conducted a power systems reliability and arc flash analysis on the existing Tram electrical system(s). Previously the electrical power system for both legs of the Arch Tram was combined into one power feed. The team separated the electrical power at the main switchboard so that each leg of the Arch could be kept operational if there were a power loss in the other leg.

The project also included the design and build of new Tram capsule doors to improve reliability, safety, and visitor experience.

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