Little Long Generating Station (207.5 MW) - Kapuskasing: Mattagami River

On January 1, 2015, the Ontario Power Authority merged with the Independent Electricity System Operator to create a new organization that combines the OPA and IESO mandates.

Please note that the information on this page is not current and will not be updated. A new format for contract data will be published soon.

The Lower Mattagami Project is a hydroelectric project that includes the addition of a new third generating unit to the existing two-unit Little Long Generating Station.

Existing Facility

The existing Little Long facility includes two vertical propeller turbine-generator sets, penstocks and draft tubes, and three existing single-phase transformers. Little Long has been in-service since the mid-1960’s.

Located 80 km north of Kapuskasing, Ontario, the facility is operated remotely from OPG’s Northeast Control Centre located at the Porcupine Transformer Station in Timmins, Ontario.


The expansion includes one vertical propeller turbine-generator set, penstocks and draft tubes, and one new three-phase transformer. The addition of the new generating unit adds 67 MW to the existing capacity for a total site capacity of 207.5 MW at a head of 26.5 metres.

As part of the expansion, a tailrace gate hoisting system is installed on the existing powerhouse tailrace deck, extending over the new tailrace deck of the powerhouse extension.

Water from the Mattagami River is conveyed from the existing Little Long GS intake structure for the third generator unit to the new spiral case via a concrete encased steel penstock.

Water from the new generating unit is returned to the Mattagami River via the existing 800 metres long tailrace canal.

The new generating unit is installed at the existing concrete structure. All three generating units share the same gravity dam and powerhouse.

The new generating unit is connected to Hydro One’s 230kV H22D circuit at the Little Long GS switchyard.

Location: Mowbray Township, Ontario
River System: Mattagami River
Nameplate Capacity: 207.5 MW
OPA Contracted Capacity: 207.5 MW
Operator: Ontario Power Generation
Technology: Hydroelectric
Turbines: Three vertical propeller turbines
Originally Built: Mid-1960’s
Coordinate: 50° 00’ 17” N, 82° 09’ 55” W


Project Progress (March 31, 2014)

  • Commissioning tests successfully completed and the upgraded facility in commerical operation at the end of the quater


Ontario Power Generation Inc.

Project Contacts:

Ontario Power Authority
Media and Public Relations
T. 416-969-6307 or 
Ontario Power Generation Inc.

Media Relations
T. 416-592-4008 or