Get Full Government Meeting Transcripts, Videos, & Alerts Forever!
Get email alerts on the Dam Safety topic
No spam. Unsubscribe anytime.
NH DES outlines fall plan to lower Merrill Lake, remove silt and install sluice gate
Summary
New Hampshire Department of Environmental Services officials described a planned October drawdown at Merrill Lake to remove seven feet of silt behind deteriorating stop logs and to replace the stop-log system with a stainless-steel sluice gate to improve dam safety and flood response.
At a Selectmen meeting, New Hampshire Department of Environmental Services (NH DES) dam officials described a planned fall drawdown and repair project at the state-owned Merrill Lake dam to remove silt and replace failing stop logs with a stainless-steel sluice gate.
Dan Matani, chief of operations at the DES Dam Bureau, told the board the bureau oversees roughly 200 state-owned dams in New Hampshire and that Merrill Lake’s wooden stop logs have deteriorated over decades. "If it's in the middle of the summertime, you could lose your lake," Matani said, describing the risk if the stop logs fail unexpectedly. He said the DES intends to schedule work in the fall when lake levels are typically lower and autumn runoff and spring snowmelt allow refilling.
Matani said silt has accumulated “about 7 feet high” behind the stop logs, which both blocks access to a low-level outlet and would make emergency responses difficult. He described the current stop logs as stacked wood planks, with eyelets that operators can hook to remove them, but said the wood and eyelets have deteriorated and may not be removable in an emergency. "We're gonna put a gate in," Matani said, describing a plan to install a roughly 4-foot-wide, 7-foot-high stainless-steel sluice gate with a threaded stem to replace the stop logs. He added the gate will provide higher discharge capacity and be easier to operate than stop logs.
DES staff said the construction crew will excavate a channel in front of the outlet and remove silt so operators can access both sides of the outlet and operate the low-level outlet if needed. The bureau has discussed the timing and potential impacts with New Hampshire Fish and Game and researchers at Hubbard Brook so those stakeholders can plan work around the drawdown, Matani said. The bureau estimated the gate installation work will take about four weeks and will be weather dependent; Matani also said DES policy requires gates on dams to be exercised and maintained at least once a year.
No formal vote or town action was taken during the presentation. Board members and residents asked clarifying questions about the composition of the silt and the road and parking surface near the work site; Matani said past work found mostly leaf and weedy material and that DES construction staff will coordinate sand relocation and other details with local contacts.
The DES presentation noted the work is intended to reduce the risk of an unplanned failure, restore the low-level outlet’s functionality, and improve DES’ ability to release water ahead of major storm events. The bureau did not provide a firm start date beyond indicating fall work is planned and that refilling would occur with autumn and spring runoff.
