Ontario Power Generation

ARNPRIOR STATION

PLANT GROUP: Ottawa/St. Lawrence Plant Group
DRAINAGE BASIN: Ottawa River
RIVER: Madawaska

NEAREST POPULATION CENTRE: Ottawa (64 Km (40 Miles) East)

IN SERVICE DATE:

UNIT 1 - 1976
UNIT 2 - 1977

BUILT BY: Ontario Hydro
Asset Transferred to Ontario Power Generation: April 1, 1999

NUMBER OF UNITS: 2
CONTROL: Remote from Chenaux GS

HISTORICAL NOTE:

The Ottawa-Huron forest region, which includes the Madawaska watershed, was the scene of the earliest lumbering activities in Ontario. A series of dams, log slides and booms extending from the upper reservoirs to Arnprior had been built by 1867 to facilitate log driving operations. Although the most active lumbering period was from 1860 to 1890, it still constitutes one of the main industries of the Madawaska River Valley.

By 1920, the lumbering activity had declined somewhat and the use of the river was being reoriented more toward power generation. Several dams had been built by private enterprise on the Madawaska's tributaries for the generation of direct mechanical power.

As early as 1928, studies had begun on the river's power potential. In 1936, nine potential sites for base load power development were selected between Racket Rapids and Arnprior for a total developed head of 196 m (645 ft).

In 1940, it was decided to build a 47 m (154 ft) head, 40 MW base load generating station at Barrett Chute (see Barrett Chute) and to rebuild or rehabilitate several abandoned logging dams in the upper reservoir in order to meet the storage requirements for this power plant. The lakes so created or restored, together with the associated network of construction roads, contributed to the development of the upper Madawaska River Valley as a major recreational resource for Ontario.

After assessing various proposals for development downstream from Barrett Chute, approval was given for construction in 1945 of a 46 m (150 ft) head, 60 MW, base load generating station at Stewartville (see Stewartville).

With increasing demands for power in the early 1960's, it was considered advantageous to add some hydraulic peaking capacity to the Ontario system. The redevelopment of the Madawaska River for peaking operation from Black Donald Lake (Mountain Chute) to the Ottawa River with a total head of 172 m (565 ft) was considered practicable and economical. The engineering plan of redevelopment for peaking involved a series of dams, including one towards the mouth near Arnprior, so that all the stations on the river could be operated in step, with a minimum of water spillage and little water level fluctuation regardless of flow through the system.

Decisions were made to immediately proceed with the most economical installations - a new dam and generating station at Mountain Chute and extension of both Barrett Chute and Stewartville Generating Stations to add a total of 343 MW of peaking capacity to the system by 1969.

The Arnprior project was not committed at that time because the above installations provided sufficient peaking capacity to meet the current demand and because the proposed Arnprior generating station was not considered economical by itself.

It was in 1971 that it was decided to build the Arnprior station. The main purpose of building at Arnprior was to correct environmental problems associated with the water level fluctuations, bank erosion and turbidity along the lower Madawaska. These are believed to have been brought about by the operation of hydroelectric plants further upstream, in particular, the Stewartville station 13 km (8 miles) to the southwest.

It was finally decided to build the Arnprior station subject to three constraints. Firstly, geological conditions had to be satisfactory. Secondly, the project had to be acceptable to regulating authorities and the Arnprior community. Thirdly, with the predicted improvement in environmental conditions along the lower Madawaska, operation as peaking plants would continue. Peaking plants store water during the hours of low electrical consumption, releasing it through the turbines at times of high or peak demand.

Field investigations quickly showed the site was technically feasible. Agreement of the municipalities, which included the town of Arnprior and townships of Pakenham, Fitzroy and McNab was obtained and on June 6, 1972 approval was announced in the Ontario Legislature.