Loon Pond Dam

Lincoln, NH

The high quality water of Loon Pond, impounded by Loon Pond Dam and remotely located in the White Mountain National Forest atop Loon Mountain, is vital to the Town of Lincoln for its auxiliary and emergency public water supply. Facing the deterioration of the Dam and orders from NHDES Dams Bureau, the Town engaged SA to evaluate the Dam, prepare design and permitting for its replacement (reconstruction), as no other source of similar water quantity and quality is available to the Town. The low-hazard Dam is 90-ft. long, 9-ft. high and impounds a volume of about 40 million gallons.

SA inspected the previous dam and surrounding rock joint structure on which it is founded, and evaluated hydrology, hydraulics and dam stability. As “Design Engineer” under NHDES Dam Safety Rules, SA designed a replacement concrete dam pinned to the rock foundation with rock dowels, designed to knit together jointed bedrock and act monolithically with dam.

The replacement dam design included new mechanical slide gates, designed for operation under snow and ice loads, capability of future remote operation, and redundancy for maintenance and emergency operations. SA designed improvements to the remote dam-access road in consideration of emergency and winter snow cat access, and crossing of existing snowmaking pipelines owned by adjoining ski resort. SA prepared design drawings, specifications, and engineer’s cost estimates in consideration of construction in this difficult access, remote location, as well as bid documents and construction contract.

SA prepared and submitted permit applications to NHDES Wetlands and Dam Bureaus and for extensive review by United States Forest Service (USFS). SA coordinated third-party NEPA review for USFS on behalf of the Town to speed the permitting. SA advertised and administered the construction bid, reviewed qualifications of low bidders, and consulted with the Town in selecting a contractor. SA managed the Project during construction on Town’s behalf, observing construction for conformance with contract documents, documenting construction and reporting to NHDES Dams Bureau to meet NHDES dam regulations as “Construction Engineer.” SA administered the construction contract, reviewed contractor invoices, negotiated change orders, and managed contract close-out. Post-construction, SA designed solar-powered, remote operation upgrades for the new gates to allow operation from the Town’s water treatment plant.