POTSDAM — A multi-phase $25 million project aimed at stabilizing a century-old underground canal is underway in an attempt to handle 21st century rainstorms.
The approximately 100-year-old canal, which has its headwaters in some wetlands northeast of the village, into the town, serves roughly the most densely populated area of the village, said Fred J. Hanss, Potsdam’s planning and development director.
“It’s a 100-year-old infrastructure and it’s in poor condition, it’s largely underground, mostly in confined spaces, very difficult to work in,” Mr. Hanss said. “So you got this 100-year-old infrastructure that is being challenged by 21st century rainfall. We know that as the climate changes, we are going to see more frequent rainfall events that have the potential to cause flooding.
The canal has the ability to pick up less than a 10-year storm, a three-inch rainfall event.
“The last big one that we had was in September 2010,” he said. “We had 22 days where there was measurable rainfall followed by a three-inch 10-year storm event and it overwhelmed the crosstown canal. It caused a lot of residential flooding.”
Mr. Hanss is developing an application for $250,000 in grant funding through the state Department of Environmental Conservation’s Climate Smart Communities grant program and the village has partnered with Clarkson University in the project.
The university will assist in the mapping of the canal with a laser camera that will be mounted to a self-driven robot which will travel along the canal system to record dimensions, location and areas of heavy debris.
“When we say that this is a project that is going to take some time to get done, it’s nothing that we are going to be able to do in one fell swoop,” Mr. Hanss said. “It’s a $25 million project, all in. So when we say phase one and phase two, if both of those phases are successfully funded, that’s a million dollars out of a $25 million project and it’s important work.”
The first part of the phase was completed in 2017.
“What we did in the first phase is we secured a little over half a million dollars in funding through the Community Development Block Grant Program and the St. Lawrence River Valley Redevelopment Agency and we removed some utility obstructions at Leroy Street and Pleasant Street and that improved the flow, because we had water and sewer lines that were basically bisecting the canal and robbing it both of capacity and it also reduced the flow,” he said. “But it doesn’t solve the problem.”
The village hired engineering firm, Environmental Design & Research (EDR), to do a study and they are now beginning to follow the firm’s recommendations, Mr. Hanss said.
That includes cleaning out the outlet of the canal, by lower Elderkin Street and Canal Street, where it dumps into the Raquette River, an area overgrown with brush, trees and storm debris.
Additionally, it was recommended that the village construct two fairly sizable stormwater retention basins, as the canal is unable to store storm runoff.
One basin would parallel Lawrence Avenue, between the residential units on Lawrence and the high school. The canal disappears underground behind St. Mary’s Church.
That, too, will be broken up into phases due to price.
The first phase will be renovating the inlet of the canal at St. Mary’s and fit it out to put steel plates to hold stormwater back and reduce the flow.
The last two phases include excavating a portion of that stormwater basin and extending the basin again, so it will end up with the needed storage capacity.
“So if we can slow that stormwater down, hopefully it will relieve the flooding issue we have,” Mr. Hanss said. “It will also clean up the water that is going into the river because if it is sitting in a stormwater basin, it’s going to dump sediment there as opposed to dumping it in the canal or into the Raquette River.“
It is estimated that the outlet improvement will improve the outlet capacity to pass a 10-year storm of greater intensity. It will also begin to increase the canal system capacity to a 50- to 100-year storm, Mr. Hanss said.