About the River

The Massena Power Canal, which connects the St. Lawrence Seaway to the lower Grasse River, and associated powerhouse were constructed in the early 1900s to provide hydroelectric power to the local community and to the “new” aluminum smelting facility. Shortly after its construction, the lower Grasse River was widened and deepened to accommodate the additional flow being diverted from the St. Lawrence Seaway through the Power Canal. The use of the Power Canal for power generation continued over the next several decades to support the growing population in Massena. Operation of the Power Canal ceased in 1958, upon completion of the Eisenhower locks system and Moses-Saunders Power Dam (FDR project) on the St. Lawrence River, which is operated by the New York Power Authority.

The deepening of the lower Grasse River many years ago altered the physical characteristics of the river. The river's banks are steep, and they extend from shallow shoal areas along the shorelines to a relatively deep and flat river bottom that is underlain by bedrock, glacial till or pre-glacial marine sediments. On average, the lower Grasse River is about 400 to 600 feet wide and 10 to 25 feet deep, and has minimal floodplains.

Typical cross sections in the portion of the river near the
Village of Massena (left) and in the lower Grasse River (right).

Grasse River Cross Section

In addition, stopping the water flow through the Massena Power Canal in 1958 significantly reduced the volume of water that is transported through the oversized lower Grasse River channel, which has resulted in low flow velocities throughout the river. Under typical summer flow conditions, flow velocities in the lower Grasse River are generally so low that it can be difficult or impossible to measure with conventional equipment. Even under higher spring flows, flow velocities are still relatively low. These low flow velocities, coupled with the deeper waters that exist in the lower river, create an environment that is favorable for the depositing of solids entering from upstream into the lower Grasse River, making it act more like a reservoir than a river. Because of this, historically, an average of 2 to 3 centimeters of clean solids have been deposited on the river bottom each year. More recent estimates suggest an average rate of about 1 centimeter per year or less.