SCHENECTADY — It’s been two winters since a historic 17-mile-long ice jam in the Mohawk River led to significant flooding in the low-lying parts of the Stockade neighborhood — and the reasons such hazardous ice jams occur remain a matter of debate.
While the federal government’s re-licensing of the Vischer Ferry hydro-electric dam could provide a new opportunity to examine the causes of such events, the New York Power Authority continues to resist the idea.
Many experts say winter ice jams and the water fluctuations when they break up are a more common cause of flooding in the Schenectady section of the Mohawk than storm runoff, which is what caused the severe flooding during tropical storms Irene and Lee in 2011.
“That’s certainly true of the flooding in the Stockade,” said John Garver, a geology professor at Union College who has studied Mohawk River flooding for more than two decades.
The Schenectady County Legislature last week added its voice to those of state Assemblyman Phil Steck and others who say the Federal Energy Regulation Commission’s relicensing review should require a study of what role the Vischer Ferry dam plays in the frequency of flooding upstream from the dam.
FERC could require a flooding study as part of the New York Power Authority’s license renewal application. While the dam’s current 40-year license doesn’t expire until 2024, decisions about studies will be needed are being made over the next few months. NYPA is opposed to doing any additional flood studies, saying the issue has already been studied.
The Power Authority is also applying simultaneously to re-license the Crescent dam, about 10 miles downstream. However, the Schenectady flooding concerns are entirely related to the Vischer Ferry dam, about eight miles below the Stockade.
While NYPA is planning studies that focus on the dam’s impact on fish, water quality and wildlife, the County Legislature urged that an ice jam-specific flooding study be added, noting advance in flood prediction modeling.
“Technology advances could give the ability to predict and respond to storm and high-water events, reduce flooding, and mitigate the risk to roadways, properties and structures within the community,” stated the resolution, sponsored by Legislator Peggy King, who lives in Schenectady’s historic Stockade neighborhood.
The resolution will join other correspondence being sent to the FERC, as it reviews public comments on the Power Authority’s initial study plan, which was released in September.
Steck has already written the agency, saying ice-jam flooding needs to be studied separately from other flooding issues.
“We believe the effect of (the dam) in exacerbating the problem of ice jam flooding has not been studied by government,” Steck wrote in October, in response to the initial Power Authority conclusion that flooding has been studied enough.
“It is likely that the current dam structures on the river contribute to or cause flooding in the historic Stockade,” Steck, D-Colonie, wrote in an earlier letter, in August. “It is critical that before any relicensing of these man made structures is allowed, there must be a comprehensive study or modeling on the formation of ice, flow of ice jams, and points were ice gets obstructed.”
The dam was built in 1913, to generate electricity and improve the functioning of the Erie Canal system. It stretches more than 1,900 feet across the river, between the Niskayuna shore in Schenectady County and Clifton Park in Saratoga County. It impounds water for about ten miles, back to Canal Lock 8
According to Garver, the dam could be contributing to flooding by trapping sediment, thereby narrowing the river channel; facilitating the formation of a thick ice sheet on the surface water behind the dam; and by reducing the surface speed of the river, making it easier for ice sheets to form.
“A major concern is that since dam construction, sediment has built up and accumulated, and these slugs of sediment may have reduced the channel width, and thus when ice floes move downstream to the sediment forces lateral shortening and jamming,” Garver wrote in a letter to FERC in August.
He said possible solutions to the problems could include removal of the dam, which some environmental groups say should be seriously examined; significant lowering of water levels behind the dam immediately prior to jam breakups to fracture and break up the ice; or the ice could be manually broken up behind the dam.
“If nothing else, consideration should be given to implementing a funding solution for an expanding jam monitoring system,” Garver wrote the regulating agency.
Some private citizens who have studied the matter have also written. “I am convinced that flooding is a valid concern and should be included in the proposed studies for relicensing the Vischer Ferry Dam hydroelectric plant,” wrote Russell Wege of Glenville, a retired engineer who studied the dam in the 1970s while working for the state Department of Environmental Conservation.
FERC will be taking public comment on the Power Authority’s proposed study plan through Dec. 22. The Power Authority is then to submit a revised study plan by Jan. 21, and FERC will decide whether to approve the plan by late February.
The Power Authority’s position is that the matter has already been studied, and the dam’s operation has little impact on upstream flooding. “Because the existing information is clearly sufficient to evaluate the flooding issue, the Power Authority is is not proposing a Vischer Ferry flooding study,” it said in the initial plan filed with FERC in September.
The urgings to FERC are just the latest effort to determine what causes the near-annual flooding in the Stockade. Concerns about flooding were brought to a head by the flooding from tropical storms Irene and Lee, and arose again with the extensive ice jam in the winter of 2017-2018.
The DEC is conducting a $500,000 study of ice jams and flooding that was commissioned in November 2018, and is looking at ice jam issues along the entire length of the Mohawk.
“The first phase of the project is completed and entailed engaging with communities along the Mohawk River to identify high-risk areas from a flood and ice jam perspective,” DEC said in a statement on Friday. “These high risk areas will be further evaluated through additional field work and hydraulic modeling. Once finished, a draft report will be issued containing specific mitigation projects that can be implemented to further reduce flooding in these communities.”
DEC is working with the state’s Re-Imagine the Canal Task Force, which was formed last summer and, in addition to looking at economic development opportunities, is doing a broader study of ice jams and flooding across the Erie Canal system.
The U.S. Geological Survey has also stepped up its monitoring of Schenectady area ice jams.
Environmental groups like Riverkeeper have expressed concerns about both the Vischer Ferry and Crescent dams, based on their impacts on migrating fish like herring and American eel, and on other environmental grounds — but they are also concerned about ice jams.
“One of the dams contributes significantly to the formation of ice jams, which have caused such damaging flooding in Schenectady that authorities are considering a range of strategies likely to cost several millions of dollars to protect the city’s historic district,” Riverkeeper water quality specialist Jennifer Epstein wrote in a blog post last week.
Reach Gazette reporter Stephen Williams at 518-395-3086, [email protected] or @gazettesteve on Twitter.
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