Exelon's Limerick Generating Station began using a mine as a back-up water source in 2003.
Exelon’s Limerick Generating Station (LGS) is a 7000 MWt two-unit boiling water reactor facility located in Montgomery County, Pennsylvania. The station, which includes two natural-draft cooling towers as part of its closed-cycle cooling system, consumes on average 35 million gallons of cooling water per day.
Limerick’s cooling needs are met primarily by the Schuylkill River. When water use from the river is restricted it turns to the Wadesville Mine near Pottsville. Limerick began using the mine as a back-up water source in 2003, as part of a Mine Water Demonstration Project. Prior to that a second water intake, built as part of the original design, on the Perkiomen Creek in Montgomery County was used when Schuylkill River flows were insufficient to meet the water needs of the plant. Water was pumped into the Creek from the Delaware River via a water diversion system.
Water pumped from the underground mine flows through the East Norwegian Creek and Norwegian Creek into the Schuylkill River. Allowing for water time of travel and evaporative losses en route, Exelon can then withdraw the augmented water downriver at the Limerick intake on the Schuylkill River.
Exelon says that, unlike some sources of mine water, discharges from the Wadesville Mine Pool are neutral pH, low acidity and high alkalinity, which improves the buffering capacity of the receiving stream. Project monitoring has shown that withdrawal of the consumptive cooling water makeup needed by Limerick did not cause downstream dissolved oxygen to fall below water quality standards. It also supported the elimination of the temperature restrictions so that Limerick can now withdraw consumptive makeup water needed with no augmentation, as long as river flows remain above 560 cubic feet per second, as provided for in the plant’s Delaware River Basin Commission (DRBC) Docket.
Another significant feature of the project has been the creation of a Restoration and Monitoring Fund (RMF), which funds projects designed to improve water quality within the Schuylkill River Basin. Exelon has provided $1.3 million to the RMF, it says.