Smart Energy Plan

October 10, 2025

Storm-hardening the Grid in South St. Louis County

Smart Energy Plan improvements will support reliability for thousands of customers.

Sub-transmission circuits are the backbone of your local energy grid. They bridge the gap between high-powered transmission lines and the lower voltage circuits powering your home. Through the Smart Energy Plan, Ameren Missouri is upgrading and storm-hardening some of its oldest sub-transmission lines to support greater reliability.

One such project involves rebuilding more than five miles of 34kV (kilovolt) circuit along Telegraph Road in south St. Louis County. When complete, the project will offer several upgrades that benefit reliability for thousands of customers in the area.

More than 50% of the poles along this stretch were past their intended useful life of 45 years, making them more susceptible to damage and therefore less reliable. In addition to newer, thicker wood poles, the line is also being rebuilt to storm-hardening standards. That includes the installation of more than two dozen composite poles. These poles are stronger than wood poles and help speed restoration by preventing cascading damage.

“We’re making a number of improvements that make a big impact on reliability, while keeping costs low for customers” says Matt Bryant, director of Ameren Missouri’s Mackenzie district, which covers the southern part of the St. Louis metro area. “Upgrading to armless insulators is a great example of that. This design is stronger and more compact than traditional cross-arms, and that helps reduce the risk of damage and lowers long-term maintenance costs.”

The wire itself is also getting an upgrade, from an all-aluminum conductor to a steel-reinforced aluminum. Not only is it a stronger material, the new wire also has more capacity to meet modern demands. The added capacity is particularly important for supporting reliability during times of peak energy demand in summer.

The project also calls for the undergrounding of the circuit where it crosses Interstate 255 west of Telegraph. This supports greater reliability by eliminating long spans of overhead wire and improves safety by eliminating the risk of wires falling across the highway.

More than 3,000 customers are directly supported by the upgrades to the line along Telegraph. But the benefits extend throughout south St. Louis County. For instance, the newly rebuilt line will enable future upgrades to a substation serving more than 4,000 customers in Oakville. The line upgrades are expected to be completed in 2026.