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Muddy Run Pumped Storage Facility

Muddy Run Pumped Storage Facility

Muddy Run Pumped Storage Facility is a pumped-storage hydroelectric plant that is owned and operated by Exelon Power, a business unit of Exelon Generation. It is used to generate electricity for peak demand which usually occurs during the morning and early evening hours.

The 8-unit power station provides 1,070 megawatts (MW) of electricity by damming the Muddy Run ravine from its mouth.  The station’s output is critical to meeting the dynamic peak electricity demands on the area’s regional power grid on hot summer afternoons.  To generate electricity, the water in the upper reservoir at Muddy Run is used to fuel the turbines, flowing into the Conowingo Pond, a 14-mile stretch of the Susquehanna River in Maryland.  As electricity demand decreases, at night, the units are reversed and used as pumps to fill the upper reservoir for subsequent peak-demand periods.

Muddy Run has provided electric power to the regional transmission system since commercial operation began in 1966. At the time, it was the largest pumped-storage hydroelectric power plant in the world.  The general plant configuration remains the same as the original construction, however, the turbines and generators have been recently refurbished.


Muddy Run has a license issued by the Federal Energy Regulatory Commission (FERC) that expires August 31, 2014. Exelon wishes to preserve this virtually emissions-free generating capacity and its electrical output, while enhancing both the environmental integrity and local community relationships.  

Typically, a FERC license is issued for a period from 30 to 50 years.  Exelon filed an application to relicense Muddy Run with FERC in August 2012.  Learn more about Muddy Run relicensing efforts.

Supporting the Local Economy

Exelon Generation spends more than $40 million annually to operate and maintain both Conowingo and Muddy Run and pays nearly $5 million in property taxes annually.  The plants have a shared workforce of over 60 Exelon employees.

Emergency Planning

Muddy Run employs sophisticated emergency response plans to protect public health and safety.  These plans are reviewed and approved by state governments and regulatory agencies.  The emergency planning includes coordination with local counties, municipalities and school districts.

Community Involvement

Muddy Run aims to be a good neighbor and is very active in the local community.

  • Charitable Giving & Volunteering.   Muddy Run and its employees give generously to the community through a variety of charitable activities including the local United Way chapters, the Airville Fire Company and Operation Warm. 
  • Recreation.  The Muddy Run Recreational Park contains a 100-acre lake surrounded by 700 acres of wood and field areas. The habitat is home to Eastern blue bird and other songbirds, bald eagles, ducks, geese and white-tailed deer, among many other creatures. The park provides family recreational needs, including camping, biking, hiking, boating and fishing. The park includes a campground and a boat launch with electric and rowboats available.

Vice President, Mid-Atlantic Region, Exelon Power: Bill Swahl

General Manager: Archie Gleason

172 Bethesda Church Rd West
Holtwood, Pennsylvania

  • Number of units: 8 units; driven by water from reservoir
  • Capacity: 1,070 MW
Muddy Run Pumped Storage Facility