After Oroville, attention turns to New York dam safety
Residents understood that if the sirens sounded at Gilboa Dam in Schoharie County that meant the dam was about to give.
During Hurricane Irene, in August 2011, with rain coming in sideways and water flowing on roads like streams, an alert was issued for the dam, which was inundated with surging waters, located just west of Albany.
State Assemblyman Peter Lopez, a Republican who represents the area, said he was told that meant a breach was possible.
“Blow the dam sirens,” he said.
The dam was never compromised, but an evacuation was issued for more than 200,000 residents in the line of a downstream gush due to the storm surge. Lopez said that storm, as well as Tropical Storm Lee the same year, showed that agencies that operate dams and reservoirs had a “social responsibility” to take on flood-mitigation as part of their operations.
The Gilboa Dam, like the Kensico and New Croton dams in Westchester County, are maintained by the New York City Department of Environmental Protection.
“Part of the challenge is that when these dams and these reservoirs were created, flood mitigation, flood control was not intended, nor designed into their structures,” he said.
The ongoing Oroville Dam situation in California has brought renewed attention to the country’s aging dam infrastructure and sparked concerns if inspections are conducted regularly enough to ensure safety for people in the area.
When officials noticed a hole had formed in the spillway of the Oroville Dam in California last week, more than 180,000 people were evacuated amid heavy rainfall. An emergency spillway began to erode and panic arose that the erosion could cause a dam breach. Residents were allowed to return but are on alert for another possible evacuation. As the San Jose Mercury News recently pointed out in a story, the same phenomenon nearly caused the collapse of one of America’s other largest dams, Glen Canyon, a 710-foot tall behemoth on the Colorado River, in 1983. That saga was captured in a book called 'The Emerald Mile."
Study of dams proposed
State Sen. David Carlucci, a Rockland County Democrat, is proposing a state bill to study the safety and condition of New York’s water infrastructure in light of the situation. Carlucci held a press conference Friday to unveil the law and release the findings of an analysis looking at the potential impact of breaches at all dams of varying sizes in Westchester and Rockland counties.
There are 258 dams in Westchester and 81 in Rockland, according to the study. The study lists the last inspection by the state Department of Environmental Conservation and categorizes each dam’s hazard level based on anticipated effects from a possible breach. Thirty-three Westchester dams and 13 Rockland dams were found to be a "Class C" high-hazard level, Carlucci’s report said.
Examples of where class C dams exist include Grassy Sprain Reservoir in Yonkers, Mamaroneck Reservoir in Harrison, Kensico in North Castle and Lake Sebago Dam in Lake Sebago.
In a statement, Carlucci said proposals to invest in water infrastructure combined with a study would help prevent damage such as that experienced in California.
"These two actions put together will allow the money to be targeted to the infrastructure that is most in need of repair, some of which is right in our backyard," he said.
In New York, dam safety has been a priority for years, DEP spokesman Adam Bosch said. The Kensico Dam in Valhalla underwent much scrutiny after Sept. 11, 2001, with many fearing it could be a terrorist target just 30 miles from downtown Manhattan.
Kensico, which holds back 30.2 billion gallons of water, could cause floods up to 70 feet in parts of White Plains if breached and affect 200,000 residents, estimates say. As a protective measure, DEP closed the roadway over Kensico in the days following Sept. 11 and have placed barriers on either side of the road in addition to other security measures.
The DEP is modernizing and upgrading its dams on a rolling basis. The dams on the Croton system were updated in the 1990s and early 2000s, while Gilboa was rehabilitated in a recently-completed $138-million project.
“What’s more, almost all our dams are now equipped with monitoring instruments,” Bosch said. “Many of these instruments report their data back to our dam safety engineers and water supply operators in real time.”
Data in most cases correlates closely to reservoir water storage, he said, and deviations are analyzed by staff — and in some cases trigger an alarm.
Bosch called DEP’s safety programs “one of the most robust and meticulous” in the country. Dams are inspected visually almost daily by DEP police, he said, and by watershed maintenance staff. More detailed inspections are conducted monthly by supervisors and at least twice a year by licensed professional engineers.
The frequency of DEP inspections can increase if an event, such as a flood occurs and each DEP dam has an “emergency action plan” that outlines protocol if a concerning condition is found. The department includes maps for potential inundation updated regularly by experts, he said, and DEP conducts annual orientation sessions for local emergency responders at each department-run dam.
Dam safety workshop
In September 2016, Westchester County sponsored a dam safety workshop, according to a county spokesman, the state Department of Environmental Conservation and the DEP. Fifty-five local government officials from the county participated. Training was specific to dams and those emergency plans. The county Department of Emergency Services has copies of the action plan and routinely analyzes protocol and conducts drills in the event of a hazard, in which the county is expected to coordinate emergency services from local communities.
The state Department of Environmental Conservation also does bi-annual inspections.
Assemblyman Lopez said he and his neighbors know what’s at stake. Between Lee and Irene, his parents and sister were displaced, and his parents’ home was flooded with eight feet of water, he said.
“Those of us who live downstream live in the shadow of these dams and there’s a palpable, almost physical presence, with the threat of the failure of these dams,” he said. “For those of us who’ve lived through it, we have a different appreciation of this vs. people who may be on the outside looking in.”