Gilman

Connecticut River· Coos, New Hampshire· Built 1898· Concrete· 38 ft tall
Low Hazard Hydroelectric Private

Key Takeaway

Gilman is classified as low hazard in New Hampshire. It was completed in 1898 and is 128 years old. Its primary use is hydroelectric.

Physical Details

Dam Height 38 ft (taller than 92.3% in NH)
Dam Length319 ft
Dam TypeConcrete
Max Storage705 acre-ft
Normal Storage705 acre-ft
Surface Area130 acres
Drainage Area1,514 sq mi
Max Discharge3,538 cfs
Year Completed1898 (128 years old)
NID IDNH00366

Safety Information

Low Hazard

No probable loss of human life and low economic/environmental losses expected.

Hazard potential describes downstream consequences of failure, not the dam's current condition. What does this mean?

Emergency Action Plan: No
Last Inspection: June 12, 2017
State Regulated: Yes
Regulatory Agency: NHDES DAM BUREAU

Ownership

Ampersand Gilman Hydro LP

Private

Nearby Dams

Faraway Pond Dam

Coos, NH

Significant Hazard 20 ft

Miles Pond

Essex, VT

Significant Hazard 19 ft

Burns Lake Dam

Coos, NH

Low Hazard 13 ft

Whitefield Lagoon Dam

Coos, NH

Significant Hazard 32 ft

Apthorp

Grafton, NH

Significant Hazard 24 ft

Bethlehem Sewage Lagoon Dam

Grafton, NH

Significant Hazard 13 ft

Dells Pond Outlet Dam

Grafton, NH

High Hazard 20 ft

Baker Brook Pond Dam

Grafton, NH

Significant Hazard 11 ft

Frequently Asked Questions

What is the hazard classification of Gilman?

Gilman is classified as Low Hazard. No probable loss of human life and low economic/environmental losses expected. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.

Who owns and operates Gilman?

Gilman is owned by Ampersand Gilman Hydro LP (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.

When was Gilman built?

Gilman was completed in 1898, making it 128 years old. Many U.S. dams were built between the 1930s and 1970s during a period of major infrastructure investment.

What is the primary purpose of Gilman?

Gilman serves the following purposes: Hydroelectric. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.

How tall is Gilman?

Gilman has a dam height of 38 ft. Dam height is measured from the natural streambed at the downstream toe to the top of the dam, and may differ from the visible height.

When was Gilman last inspected?

Gilman was last inspected on June 12, 2017. Inspection dates indicate when a formal review occurred, not the results of that inspection.

Data from the National Inventory of Dams (NID) maintained by the US Army Corps of Engineers. Dam conditions may have changed since the last update. This site is not affiliated with USACE. Do not use for emergency planning — contact your local dam safety program.