Senate committee hears DEC call for preapproved dam drawdown plans in H.397

Ben Green, section chief of the Dam Safety Program at the Department of Environmental Conservation, told the Senate Committee on Government Operations on April 16 that dam owners who want to use temporary waivers to perform pre‑flood drawdowns should be required to prepare preapproved drawdown plans that specify communications, drawdown rates and monitoring.

Green said the Dam Safety Program regulates about 1,000 non‑hydropower, nonfederal dams in Vermont and acts as state owner representative for 13 state‑owned dams, including the Winooski River flood‑control dams at Waterbury, Wrightsville and East Barre. He said his program has seven staff and that the Vermont Agency of Natural Resources is the single largest dam owner in the state when other agency holdings are counted.

"Preplanning is really necessary for this to be a successful initiative," Green said, urging that plans include downstream notifications, modeling of reservoir and channel hydraulics, target drawdown elevations, maximum drawdown rates and monitoring requirements. He said several days' notice would be required to make drawdowns effective and avoid unintended consequences.

Green outlined potential benefits and risks. He said limited, controlled drawdowns can reduce overtopping risk and use existing infrastructure to attenuate floods, but cautioned that most Vermont dams were not designed primarily for flood control and so benefits vary by dam. He cited two examples from the department’s recent studies: Noyes Pond Dam in Groton, which hydraulic modeling shows provides little flood attenuation; and Silver Lake Dam in Barnard, which provides substantial storage and passes little flow during floods.

Green warned that overly rapid drawdown can damage earth‑embankment dams, that outlet failures could accidentally drain reservoirs, and that abrupt downstream flows can cause channel erosion and ecological harm. He also noted winter drawdowns can create freeze‑related damage in some regions, though he judged that risk low in much of Vermont.

On thresholds and scope, Green said dams regulated by the state are typically those impounding more than 500,000 cubic feet of water (about 11.5 acre‑feet), and that small backyard ponds would generally be excluded. He said drawdown operations should be limited to dams in satisfactory condition with reliable outlet works.

Green described the existing regulatory patchwork. He said roughly 20 dams in Vermont are regulated by the Public Utility Commission and about 80 by the Federal Energy Regulatory Commission; federal dams are self‑regulating (for example, Army Corps of Engineers structures). He said many FERC‑regulated hydropower facilities already manage reservoir levels under water‑quality certifications and have operational bands that allow limited pre‑event operations.

On H.397 specifically, Green recommended adding guardrails so that any temporary waivers of environmental permits or operational bands would be accompanied by preapproved plans, modeling, notification protocols and post‑event reporting so the state can assess whether operations provided benefit. He told the committee that plan elements should include maximum ramp rates for gate operations, target outflows and requirements to restore reservoir levels once the public‑safety risk has passed.

Committee members asked about whether drawdowns can already occur during declared emergencies. Green said some drawdowns happen informally and some hydropower dams have permit mechanisms, but that a broader, reliable program would require clearer procedures and likely additional statutory language or formalized consultation with the secretary of the Agency of Natural Resources. The chair asked Green to draft specific statutory language; committee staffer Tucker Anderson was asked to work with Green on proposed guardrails.

The committee did not move H.397 at the April 16 hearing; members said they expect to consider revised language when the bill returns to the agenda next week.