Moses-Saunders Power Dam

Moses-Saunders Power Dam
R.H. Saunders Generating Station on the Canadian side of the dam
Interactive map of Moses-Saunders Power Dam
Official name	Robert Moses-Robert H. Saunders Power Dam
Country	Canada United States
Location	Cornwall, Ontario, Canada Massena, New York, United States
Coordinates	45°00′23″N 74°47′42″W
Status	Operational
Construction began	1954
Opening date	1958
Owners	Ontario Power Generation New York Power Authority
Operators	Ontario Power Generation New York Power Authority
Dam and spillways
Impounds	Saint Lawrence River
Height	195.5 ft (60 m)
Length	3,216 ft (980 m)
Reservoir
Creates	Lake St. Lawrence
Surface area	100 mi2 (259 km2)
Maximum length	30 mi (48 km)
Power Station
Commission date	1958–1959
Hydraulic head	81 ft (25 m)
Turbines	R.H. Saunders: 16 Kaplan units St. Lawrence-FDR: 16 Kaplan units
Installed capacity	R.H. Saunders: 1,045 MW St. Lawrence-FDR: 912 MW authorized capacity

The Robert Moses-Robert H. Saunders Power Dam, commonly known as the Moses-Saunders Power Dam, is an international hydroelectric dam spanning the Saint Lawrence River between Cornwall, Ontario, Canada, and Massena, New York, United States. The structure forms part of the St. Lawrence Power Project and was constructed jointly by Ontario Hydro, now Ontario Power Generation (OPG), and the New York Power Authority (NYPA).

The 1-kilometre (0.62 mi) powerhouse is divided by the Canada–United States border. Its Canadian half is the R.H. Saunders Generating Station, a 16-unit, 1,045-megawatt facility operated by OPG. The American half is NYPA's St. Lawrence-Franklin D. Roosevelt Power Project, also containing 16 generating units. The two utilities generate electricity independently while cooperating in the operation of the shared structure and management of river flows.

Construction began in 1954 and power production began in 1958. The project created Lake St. Lawrence, a reservoir extending upstream from the dam, and was developed concurrently with the St. Lawrence Seaway. Creation of the reservoir permanently altered the St. Lawrence Valley, displacing approximately 6,500 people and submerging communities that became known as the Lost Villages.

The dam is also a principal control point for outflows from Lake Ontario. Since 2017, flows through the Moses-Saunders facility have been regulated under the International Joint Commission's Plan 2014.

Background

Panorama of the dam from the United States side

Development of the international section of the St. Lawrence River for navigation and hydroelectric power was discussed for decades before construction of the Moses-Saunders project.

The Treaty of Washington of 1871 addressed navigation on waterways shared by Canada and the United States. By the late 19th century, governments and commercial interests were considering ways of creating a deeper navigation route connecting the Great Lakes with the Atlantic Ocean.

The Deep Waterways Commission was established in 1895 to study expanded navigation through the Great Lakes-St. Lawrence system.

The Boundary Waters Treaty of 1909 created the International Joint Commission (IJC), establishing a permanent binational mechanism for addressing issues concerning waterways forming or crossing the international boundary.

Large-scale development remained politically controversial, particularly in the United States, where railway and other commercial interests opposed construction of a competing deep-water transportation route.

In 1931, New York governor Franklin D. Roosevelt signed legislation establishing the New York Power Authority, creating a public agency capable of developing hydroelectric resources on the St. Lawrence River.

By 1951, after decades of stalled negotiations, Canada indicated that it was prepared to proceed with a navigation project largely within Canadian territory. Renewed negotiations subsequently produced a binational agreement for development of hydroelectric power.

The International Joint Commission approved the St. Lawrence power project in 1952.

Construction

Construction of the Long Sault Dam in 1957

The power project was constructed as part of a much larger transformation of the international section of the St. Lawrence River.

On the Canadian side, construction was undertaken by Ontario Hydro. The New York Power Authority was responsible for the American portion.

Robert Moses, chairman of NYPA, oversaw development of the American side. Robert Hood Saunders, chairman of Ontario Hydro and a former mayor of Toronto, led the Canadian power authority during the project's early construction.

Saunders died on January 16, 1955, from injuries sustained when an aircraft in which he was travelling crashed near London, Ontario. The Canadian generating station was subsequently named in his honor.

The wider project included:

• the Moses-Saunders powerhouse;
• the Long Sault Dam;
• the Eisenhower and Snell navigation locks;
• the Massena Intake;
• the Iroquois control dam;
• approximately 10.9 miles (17.5 km) of dikes; and
• extensive excavation, channel deepening and shoreline reconstruction.

Construction required portions of the St. Lawrence River to be temporarily diverted while the powerhouse and related structures were built.

The project ultimately involved tens of thousands of workers throughout the St. Lawrence Valley and was one of the largest construction projects undertaken in Canada and the United States during the 1950s.

Inundation and first power

The power project required water levels upstream of the dam to be substantially raised, creating the reservoir now known as Lake St. Lawrence.

Before flooding, residents were relocated, buildings were moved or demolished, cemeteries were transferred and transportation infrastructure was reconstructed on higher ground.

On July 1, 1958, engineers breached a cofferdam that had held back the St. Lawrence River from the newly constructed works. Approximately 27 tonnes of explosives were used.

Water flowed into the cleared valley over the following several days, forming Lake St. Lawrence.

The first generating unit at R.H. Saunders entered service in July 1958. The Canadian station's 16 units were progressively commissioned through 1959.

The American generating units entered service during the same period.

Dedication

The power project was formally dedicated on June 27, 1959.

The ceremony was attended by Queen Elizabeth II, in her capacity as Queen of Canada; United States vice president Richard Nixon; New York governor Nelson Rockefeller; and Robert Moses.

Canadian-American bandleader Guy Lombardo and His Royal Canadians were scheduled to perform, but their aircraft was diverted because of fog. Music was instead provided by the Massena Central High School band.

The St. Lawrence Seaway itself had opened to commercial navigation earlier in 1959.

Design and operation

The Moses-Saunders Power Dam spans the international boundary between Cornwall and New York's Barnhart Island.

The main structure is approximately 3,216 feet (980 m) long and 195.5 feet (59.6 m) high.

Unlike many international power projects in which electricity is generated by a single operator and divided contractually, the Moses-Saunders structure contains two independently operated generating stations physically joined into one powerhouse.

R.H. Saunders Generating Station

The Canadian portion is the R.H. Saunders Generating Station, owned and operated by Ontario Power Generation.

The station contains 16 generating units and has a maximum generating capacity of 1,045 MW.

The turbines are fixed-pitch Kaplan turbine designs suited to the relatively low hydraulic head and high water flow of the St. Lawrence River.

R.H. Saunders is Ontario's second-largest hydroelectric generating station by installed capacity.

St. Lawrence-Franklin D. Roosevelt Power Project

The American portion is operated by the New York Power Authority as the St. Lawrence-Franklin D. Roosevelt Power Project.

Like its Canadian counterpart, the powerhouse contains 16 turbine-generators.

The Federal Energy Regulatory Commission lists the project with an authorized generating capacity of 912 MW, while NYPA describes the 16-unit facility as capable of producing approximately 800 MW under current operating ratings.

The two halves of the powerhouse operate separately but must coordinate use of the shared water resource.

Associated structures

The Moses-Saunders powerhouse is one component of a larger international control system.

The Long Sault Dam, located approximately 3.5 miles (5.6 km) upstream, serves as a spillway and control structure.

The Iroquois Dam, farther upstream, is used to regulate water levels and assist with ice management and navigation.

The Eisenhower and Snell locks, located on the American navigation channel, allow commercial vessels to bypass the power project.

Dikes and other control structures help maintain Lake St. Lawrence at its operating elevation.

Water-level regulation

The Moses-Saunders Dam is the principal control structure for the outflow of Lake Ontario into the lower St. Lawrence River.

Water releases affect:

• Lake Ontario water levels;
• Lake St. Lawrence;
• downstream St. Lawrence River levels;
• hydroelectric generation;
• commercial navigation;
• shoreline properties;
• recreational boating; and
• aquatic and wetland ecosystems.

The International Lake Ontario-St. Lawrence River Board, operating under the International Joint Commission, determines regulated outflows from Lake Ontario.

Plan 2014

Since January 2017, outflows have been managed under Regulation Plan 2014. The plan replaced the earlier Plan 1958-DD framework and allows greater natural variation in Lake Ontario and upper St. Lawrence River levels while continuing to consider flood protection, navigation, hydroelectric generation and downstream conditions.

Record high-water events occurred across Lake Ontario and the St. Lawrence River system in 2017 and 2019.

In 2020, the IJC ordered an expedited review of Plan 2014. The review examined whether changes to the regulation system could improve outcomes during extreme high- and low-water conditions.

By June 2026, the six-year review was nearing completion. The IJC reported that thousands of potential modifications had been assessed, although none could eliminate flooding during extreme water-supply events because precipitation, runoff, wind and other natural factors can exceed the ability of regulation at Moses-Saunders to compensate.

Displacement and the Lost Villages

Construction of the power and navigation projects permanently transformed the St. Lawrence Valley.

Approximately 6,500 people in eastern Ontario were relocated from land that would be flooded by Lake St. Lawrence.

Ten populated communities within the flood zone became collectively known as the Lost Villages:

• Aultsville
• Dickinson's Landing
• Farran's Point
• Maple Grove
• Mille Roches
• Moulinette
• Santa Cruz
• Sheek's Island
• Wales
• Woodlands

Some buildings were physically moved to the newly planned communities of Long Sault and Ingleside, while others were relocated to Upper Canada Village.

Homes, farms, churches, cemeteries, roads and railway infrastructure that could not be relocated were demolished or abandoned before inundation.

Parts of the former landscape remain visible underwater, including roads and Lock 21 of the old Cornwall Canal.

The creation of Lake St. Lawrence also produced the chain of islands now connected by the Long Sault Parkway.

Impact on Akwesasne

Construction and operation of the power project also had substantial effects on the Mohawk Nation at Akwesasne, whose territory straddles the Canada-U.S. border along the St. Lawrence River.

Flooding associated with the project inundated reserve and traditional-use lands and affected fishing, navigation, shoreline access and other activities.

The Mohawk community was not adequately consulted or compensated during the original project.

In 2008, Ontario Power Generation and the Mohawk Council of Akwesasne entered into a Final Settlement Agreement addressing historical damages associated with construction and operation of the R.H. Saunders Generating Station.

OPG issued a formal apology, and the agreement included financial compensation and commitments related to environmental stewardship, employment, economic opportunities and the relationship between the utility and Akwesasne.

The partnership has subsequently included environmental and cultural initiatives.

In 2024, an expanded Indigenous garden opened at the Saunders Hydro Dam Visitor Centre in Cornwall. Developed in consultation with Akwesasne, it includes plants and interpretive features of cultural significance to the Haudenosaunee.

Environmental effects

Creation of Lake St. Lawrence altered river currents, wetlands, spawning areas and shoreline habitat.

Fish populations affected by changes to the river system have included American eel, lake sturgeon, northern pike, walleye and muskellunge.

The American eel was particularly affected because hydroelectric dams interrupted its migration between freshwater habitat in the Great Lakes-St. Lawrence watershed and its ocean spawning grounds.

American eel passage

An eel ladder was constructed at R.H. Saunders to assist juvenile American eels migrating upstream.

The original facility used a former ice sluice to provide a route around the generating station. It was later enlarged and improved.

OPG also developed trap-and-transport programs and other measures intended to reduce the effect of the generating station on downstream-migrating adult eels.

Environmental work associated with the project has also included fish-habitat restoration, shoreline projects and changes to generation operations during sensitive periods.

On the American side, environmental and recreational programs were incorporated into NYPA's federal relicensing agreements.

Rehabilitation and modernization

Because the generating station was constructed during the 1950s, both utilities have undertaken extensive modernization programs intended to extend the life of the facility.

Concrete expansion

Engineers identified alkali-aggregate reactivity in the concrete at R.H. Saunders during the 1970s.

The chemical reaction causes portions of the concrete to slowly expand. Around the generating units, this expansion can distort turbine throat-ring liners and other structures if left uncorrected.

Between 1993 and 1996, narrow slots were cut into expansion joints between the generating units to relieve accumulated pressure.

OPG repeated the slot-cutting program between 2017 and 2019 using diamond-wire cutting equipment.

The design of replacement turbine components has also been modified to accommodate continued concrete movement.

Canadian unit overhaul

In January 2023, OPG began a major refurbishment program covering all 16 generating units at R.H. Saunders.

The program began with Unit G9 and is expected to continue unit by unit until approximately 2039.

Work includes replacement of the 62-tonne (68-short-ton) turbine runners, installation of more efficient designs, replacement of throat-ring liners and refurbishment of electrical and mechanical equipment.

OPG expects the new runners to generate electricity more efficiently using less water, while extending the operating life of the station by several decades.

The refurbishment maintains the station's 1,045 MW of renewable generating capacity.

American modernization

NYPA began a Life Extension and Modernization Program for the St. Lawrence-FDR station approximately 40 years after the project first entered service.

The 15-year program represented an investment of approximately US$281 million and replaced or refurbished much of the original powerhouse equipment.

NYPA has continued capital improvements at the St. Lawrence facility, including work on generating-unit rotors and other major equipment.

The American project operates under a 50-year Federal Energy Regulatory Commission license issued in October 2003.

Economic role

Hydroelectric power from the St. Lawrence project has played an important role in the industrial development of northern New York and eastern Ontario.

On the New York side, allocations of low-cost St. Lawrence-FDR electricity have historically supported industrial facilities in the Massena area, particularly aluminum production.

NYPA continues to allocate project power for economic-development purposes in northern New York.

The Canadian station forms part of Ontario Power Generation's regulated hydroelectric fleet and can provide enough capacity to meet a significant portion of Ontario's electricity demand during operation. OPG has stated that the 1,045 MW station is capable of producing enough electricity for more than 800,000 homes and can supply up to approximately five percent of Ontario's electricity needs under suitable conditions.

The generating station also remains a major employer in Cornwall. OPG reported approximately 110 employees at R.H. Saunders in 2023.

Visitor centers and interpretation

Public interpretation facilities operate on both sides of the international project.

Saunders Hydro Dam Visitor Centre

The Saunders Hydro Dam Visitor Centre is located on Second Street West in Cornwall near the Canadian generating station.

The center contains exhibits concerning hydroelectric generation, the St. Lawrence Seaway and Power Project, the Lost Villages, local ecology and the Mohawk Nation at Akwesasne.

It also serves as a community and educational facility.

An expanded Indigenous garden developed with the Mohawks of Akwesasne opened at the site in 2024.

Hawkins Point Visitors Center

On the American side, NYPA operates the Frank S. McCullough Jr. Hawkins Point Visitors Center near Massena.

The center includes exhibits concerning electricity, energy conservation and the history of the St. Lawrence project, along with an observation area overlooking the Moses-Saunders dam.

See also

• St. Lawrence Seaway
• Lost Villages
• Long Sault Parkway
• Lake St. Lawrence
• Cornwall, Ontario
• Massena, New York
• International Joint Commission
• List of electrical generating stations in Ontario
• List of power stations in New York
• List of largest power stations in Canada

Further reading

• Macfarlane, Daniel (2014). Negotiating a River: Canada, the US, and the Creation of the St. Lawrence Seaway. Vancouver: UBC Press.
• Parham, Claire Puccia (2009). The St. Lawrence Seaway and Power Project: An Oral History of the Greatest Construction Show on Earth. Syracuse University Press.

External links

• R.H. Saunders Generating Station – Ontario Power Generation
• St. Lawrence-FDR Power Project – New York Power Authority
• International Lake Ontario-St. Lawrence River Board