by Thaddeus Flint
Could the Dam at Cherry Plain State Park pose a risk to the proposed high pressure gas pipeline that might one day run through Stephentown? Some residents believe yes. And whether or not the pipeline ever gets built, residents living along the Black River would still like to know what might happen should a hundred year storm – one like Hurricanes Irene or Sandy—fill the pond there to the breaking point.
[private]“The probability of a dam failure occurrence in Rensselaer County is relatively low due to routine inspection, repair and maintenance programs carried out by the NYSDEC,” states a 2011 draft Hazard Mitigation plan for Rensselaer County. “However, the possibility of a future failure event is likely increasing due to aging dam structures that may be in need of repair or reconstruction.”
The Black River Pond Dam was constructed between 1934 and 1937 by the Civil Conservation Corps. The Dam is comprised of a concrete core wall covered with an earthen embankment, with a maximum height of 42 feet and a crest width of between 20 to 24 feet. The concrete core appears to be around 12 feet high. The dam has a 210 foot spillway as well as a 24 inch low level output pipe.
The dam is owned by the NYS Office of Parks, Recreation and Historic Preservation (NYSOPRHP), but the NYS Department of Environmental Conservation (DEC), oversees dam safety for the State. The DEC had previously classified the dam as Class B, “Significant/Intermediate Hazard Potential”, with Class A being the safest and Class C being the most hazardous.
“A dam is typically assigned a hazard classification based on the potential impact that a dam failure may have on downstream areas,” reads the DEC’s Draft Guidance for Dam Hazard Classification. “Residences warrant particular consideration when assessing dam failure consequences, since people may be asleep and unable to react quickly to a failure.”
A Class B dam failure, according to the DEC, “may result in damage to isolated homes, main highways, and minor railroads; may result in the interruption of important utilities, including water supply, sewage treatment, fuel, power, cable or telephone infrastructure; and/or is otherwise likely to pose the threat of personal injury and/or substantial economic loss or substantial environmental damage. Loss of human life is not expected.”
However, in 2008, a Hazard Classification Study performed at the request of NYSOPRHP, concluded that the Black River Pond Dam should be reclassified as a Class C, or “High Hazard” dam. In this case, should the dam fail, the likely result would be “widespread or serious damage to home(s); damage to main highways, industrial or commercial buildings, railroads, and/or important utilities, including water supply, sewage treatment, fuel, power, cable or telephone infrastructure; or substantial environmental damage; such that the loss of human life or widespread substantial economic loss is likely.”
With that report, not much seems to have happened for the next couple of years in regard to the dam at Cherry Plain. It stayed a Class B dam. The State has a lot of dams to worry about, over 5700 in fact, of which 686 are Class B and 392 are Class C. Rensselaer County alone has 16 of the Class B dams and nine of the High Hazard Class C dams. Four of the nine are located in Grafton, three at Grafton Lakes State Park, and one on Dunham Reservoir.
Then came Hurricanes Irene in 2011 and Sandy in 2012, two storms far more destructive than the 100 year storms the dam was originally built to withstand.
People along the Black River who saw the damage done in Schoharie County or even parts of Vermont began to wonder what was going on with the Cherry Plain Dam. Was it safe?
“I got 6.5 inches of rain in 24 hours,” during Irene says Jack Spillman of Black River Road in Stephentown. The water carved out a piece of the road and the river was coming up towards his doorsteps. Had the area behind the Black River Dam received another 4 inches, it is very possible that the spillway would have run out of room to drain the pond, forcing the water to crest the dam. A dam largely made of dirt.
“It’s not going to be much protection in terms of total collapse,” said Spillman of the earthen embankment. He said the water from Irene, not moving fast at all, managed to eat away the road by his house in less than half an hour.
“If it collapses, our property will certainly be flooded and our home may be as well,” said Sandy Nathan who lives near where the Black River crosses under Route 43 in Stephentown. “Such a collapse would probably be unpredictable, perhaps caused by an unpreventable force like the weather. Our weather over the last few years has been erratic and, at times, fearsome.”
The State appears to agree with Nathan when it comes to the weather. “Given the history of occurrences, climate change, and sea level rise, it is probable that flood hazard events will become more frequent throughout New York State,” says a 2014 NYS Hazard Mitigation Plan.
In 2014 the NYSOPRHP commissioned another report. This one came back in May, saying pretty much the same thing, that “simulation models confirm the dam should be reclassified as a Hazard Class C – the spillway has inadequate capacity to pass Spillway Design Flood without overtopping the dam.” Aecom, the company that prepared that report, recommended some ways to mitigate the possible overflow hazard. The Parks Department could either increase the length of the spillway to 262 feet, raise the height of the dam by 7.7 feet, or construct a 139 foot spillway while at the same time lowering the pond’s water level by two feet. If the third option were chosen, and if the overtopping of the dam was armored, then water level could remain the same. Whatever the route taken, it wasn’t going to be a cheap one. “Preliminary cost estimates for these concepts ranged from $1 million to $4 million in 2008 dollars,” said Aecom. That’s about $1.1 million to $4.4 million in 2015.
In October 2014 the DEC followed up that report with a visual inspection that found the “right spillway side is displaced by approximately four inches. Soil has eroded through the exposed joint…” as well as a “low area in the crest of the dam.” The DEC engineer, David Harmon, also noted that NYSOPRHP is supposed to “develop and distribute to the local emergency responders” an Emergency Action Plan (EAP). “No EAP received,” reported Harmon. It was, however, also noted by Harmon that maybe the first two reports had been too “conservative and may overestimate breach flows and depth for rainy day flows.” A new report, as yet unfiled, will supposedly suggest that the Class B rating remain. NYSOPRHP is now consulting with DEC Dam Safety regarding that reclassification, but a final decision has not yet been made.
“State Parks recognizes that our neighbors downstream are concerned about the performance of the dam during a flood event, and have undertaken operational changes to improve the safety of downstream residents,” wrote NYSOPRHP Deputy Public Information Officer Dan Keefe in an email February 5. “These measures include performing regular maintenance to ensure the dam remains in good condition and lowering water levels when significant storms are predicted.”
NYSOPRHP also notes that the hazard classifications don’t really relate to the actual condition of the dam, or, even suggest imminent failure. Rather, the classifications are based upon potential downstream impacts should the dam ever fail.
That impact might have grown since October 2014. “Now add to our worries about the poor condition of the dam, the possibility of a high-pressure fracked-gas pipeline at an elevation lower than the dam, in ground and riverbed between the dam and our home,” points out Nathan. “The route proposed for the pipeline is less than a quarter of a mile from our home; the pipes are required to be buried only three feet beneath the surface; and I understand that the gauge of the metal used in the pipes in rural areas like ours is the thinnest allowed. Add all of this up and I can envision a wall of water rushing from a collapsed dam scooping up the pipes and tossing them who knows where? If that happens, the escaping toxic gas will explode and, frankly, I don’t want to think about the ensuing cataclysm.”
And neither does Spillman, who is just upriver from where the Kinder Morgan gas pipeline is proposed to cross under the Black River. The route Kinder Morgan anticipates is one following the National Grid power lines from the Alps area North of Route 43 down into Stephentown on its way to New England and possibly beyond.
“Once it gets in your head, you really wake up,” said Spillman of what all that water could do to a pipe only three feet below a stream bed. “I’m going to be the first wiped out.” He’s seen what normal flood water can do to a road bed in half an hour and that was before the Black River really gets moving. He estimates the river drops 16 to 18 feet in the 1000 feet right before the possible pipeline crossing.
“It is recommended that Rensselaer County and any municipality potentially exposed to flooding caused by dam failure investigate the development of inundation mapping and response plans for dams where none are available or where the existing mapping is outdated or lacking in detail as part of their future hazard mitigation strategies,” says the 2011 draft Hazard Mitigation plan for Rensselaer County.
“Who’s going to pay for that?” responded Stephentown Town Supervisor Larry Eckhardt. At the moment there is no Town emergency plan should the dam come tumbling down. “This should not cost taxpayers here a penny if we have no control over it.” Eckhardt said this is something that will be brought up should the Federal Energy Regulatory Commission finally decide that the pipeline will go through the town. In the meantime the Town can’t do everything itself. “Citizens need to get involved,” said Eckhardt who specifically noted the tenacious manner in which Spillman has been following up with DEC and NYSOPRHP for years now.
A plan in this case, however, might not be all that useful should the event being planned for actually occur. A 2010 NYS Office of Emergency Management workshop on Dam Safety called it a “myth” that a “flood plan will adequately prepare a jurisdiction for a dam failure.” In fact, says the NYSOEM, “a jurisdictional ‘flood’ plan will NOT adequately prepare a jurisdiction for a catastrophic dam failure.” And that’s just a dam failure plan. It’s not a dam failure causing a high pressure gas pipeline rupture, possible explosion, and possible leaking of fracking chemicals into a river plan.
Spillman for one is not about to let that happen unchallenged. He’s pursued this quietly for years and now the outcome could be even worse than he initially thought possible.
“I’m not going to be quiet anymore,” Spillman. said. “Now, I’m going to start making a lot of noise.”
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