US Bridges

NH120 over Great Brook

Fair

Grafton County, New Hampshire · 2.3 MI from Plainfield Tl · Structure no. 014401490008600

Built
1935
90 years old
Condition
Fair
inspected June 2023
Type
Frame
Concrete
Length
40 ft
1 main span
Daily traffic
2,671
2023 count
Owner
State
State Highway Agency

About this bridge

NH120 over Great Brook is a concrete frame carrying NH120 over Great Brook in Grafton County, New Hampshire. It was built in 1935, so it is 90 years old, older than the New Hampshire average of 56.9 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 2,671 vehicles a day, roughly 4% of them trucks, projected to reach 3,953 by 2043. The structure is 40 ft (12.2 m) long and 36 ft wide. If it were closed, the detour would be 8.1 mi (13 km).

Location

Open in Google Maps
CarriesNH120
CrossesGreat Brook
Location2.3 MI from Plainfield Tl
RouteState Highway 120
CountyGrafton County
StateNew Hampshire
Coordinates43.61967, -72.22509
Functional classRural Major Collector

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJune 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating39.6 US tons
Inventory rating23.8 US tons

Structure

Structure typeFrame
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadH 15
Structure length40 ft (12.2 m)
Longest span35 ft (10.7 m)
Deck width36 ft (10.9 m)
Roadway width32 ft (9.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,671 (2023)
Projected traffic3,953 by 2043
Trucks4%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.1 mi (13 km)
TollOn a free road
National Highway SystemNo
Strategic Highway NetworkInterstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$314,000 (2025 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was NH120 over Great Brook built?

It was built in 1935, making it 90 years old in 2025.

What condition is NH120 over Great Brook in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in June 2023.

How much traffic does NH120 over Great Brook carry?

About 2,671 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is NH120 over Great Brook?

The structure is 40 ft (12.2 m) long with a longest span of 35 ft (10.7 m) and a deck 36 ft wide.

Who owns NH120 over Great Brook?

It is owned by the State Highway Agency.