Building for Reliability

Updating 69-Kilovolt Transmission Lines

SMECO is replacing four existing 69-kilovolt transmission lines from the cooperative’s switching station at the Chalk Point Generating Station in Aquasco to the Hughesville substation. The existing lines date back to the 1960s and represent some of the oldest in SMECO’s system. The cooperative has taken measures to extend the lifecycle of the existing lines, but they are in dire need of replacement because of aging conditions. Replacing them proactively reduces the need for emergency repairs and allows the cooperative to focus on other sustainability projects in our service territory.

Up to 67 percent of the cost of this project will be covered by funding from the Grid Resilience and Innovation Partnership (GRIP) grant money awarded to SMECO by the U.S. Department of Energy (DOE). Securing grants like GRIP helps offset the financial impact of necessary capital improvements on SMECO members while strengthening infrastructure for continued reliability.

This project is part of continued efforts to provide and maintain reliable electrical service for our members.

Substation Rebuilds

SMECO owns and maintains the electric systems at the Navy facilities in Southern Maryland. The cooperative recently rebuilt Substation 3 at Naval Air Station Patuxent River in St. Mary’s County and built a new dual-circuit transmission line on the base. Naval Support Facility Indian Head in Charles County is undergoing its own substation rebuild, including an updated control house, new disconnect switches, circuit breakers, current and voltage transformers, and new relaying protection.

Elsewhere, the cooperative has outfitted the Patuxent Park substation in Lexington Park with a replacement transformer. The project included changing out the bus work, disconnect switches, and circuit breakers, and installing a control house for the first time. In 2026, SMECO will perform a similar rebuild of the Forest Park substation in Waldorf.

Waldorf Expands System Capacity

Population growth in Charles County led SMECO to replace its aging Waldorf substation with a larger facility next door. The new substation has two transformers that have higher mega volt-amp ratings than the old ones, increasing the load capacity by a third. SMECO energized the facility in August 2025.

Substation transformers are huge, measuring more than a dozen feet tall and weighing more than 50 tons. SMECO decided against rebuilding the old Waldorf substation, because delivering and unloading the large equipment would have meant closing lanes on heavily traveled Berry Road for some time. So SMECO chose to acquire land behind the facility and build a new substation, one with safer and more efficient access from Western Parkway as well as more room for the upgraded equipment.

Waldorf’s new design uses a box structure that incorporates advanced modular construction techniques and compact, standardized components. The layout is SMECO’s standard where space is limited and it’s excellent for urban areas.

Crews Rebuild Marshall’s Corner

SMECO reconstructed its substation in Marshall’s Corner near La Plata, energizing the facility in February 2025. The cooperative used its own crews in the Apparatus department for the rebuild, giving them additional experience in substation construction. During the work, a mobile substation placed on the site handled the Marshall’s Corner electric load.

St. Mary’s County Substation Upgrades

Substations in Lexington Park and Milestown in St. Mary’s County went through rebuilds to expand SMECO’s load capacity and service reliability.

The cooperative finished the Lexington Park reconstruction in November 2022, replacing the facility’s two large transformers. Both sides of the facility have been upgraded with new 69-kV circuit breakers, new disconnect switches, new 15-kV main breakers, and new 15-kV reclosers. The upgrade also includes a new control house, powered by two new service transformers. The control house is equipped with a new DC power system and protection relays that serve the new transformers, breakers, and reclosers.

Milestown received one of Lexington Park’s old transformers for its own rebuild, which SMECO completed in October 2023. The construction included a box structure on the high-voltage side of the facility, a control house for the relaying and communications equipment, new circuit breakers, and new disconnect switches.

New Substation & Transmission Line in St. Mary’s County

SMECO has built a new substation in Chaptico. The facility adds capacity to our transmission system in the northern part of St. Mary’s County, absorbing some of the load from four other substations in the area. We energized the substation in 2023.

To supply electricity to the Chaptico substation, SMECO built seven miles of 69-kV transmission line from the Ryceville substation, finishing construction in November 2022. The new line uses SMECO’s existing right-of-way for the 230-kV line that connects the Ryceville and Hewitt Road switching stations.