US Bridges

Nh 31 over Stony Brook

Fair

Hillsborough County, New Hampshire · 1.5 MI FM Lyndeborough Tl · Structure no. 027701070014100

Built
1928
97 years old, rebuilt 1985
Condition
Fair
inspected April 2024
Type
Frame
Concrete
Length
26 ft
1 main span
Daily traffic
3,863
2023 count
Owner
State
State Highway Agency

About this bridge

Nh 31 over Stony Brook is a concrete frame carrying Nh 31 over Stony Brook in Hillsborough County, New Hampshire. It was built in 1928 and reconstructed in 1985, so it is 97 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 6 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 3,863 vehicles a day, roughly 4% of them trucks, projected to reach 5,717 by 2043. The structure is 26 ft (7.9 m) long and 40 ft wide. If it were closed, the detour would be 8.1 mi (13 km).

Location

Open in Google Maps
CarriesNh 31
CrossesStony Brook
Location1.5 MI FM Lyndeborough Tl
RouteState Highway 31
CountyHillsborough County
StateNew Hampshire
Coordinates42.85353, -71.76232
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionApril 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment4: Meets minimum tolerable limits to be left in place as is
Operating rating63.9 US tons
Inventory rating38 US tons

Structure

Structure typeFrame
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadH 15
Structure length26 ft (7.9 m)
Longest span23 ft (7 m)
Deck width40 ft (12.2 m)
Roadway width32 ft (9.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,863 (2023)
Projected traffic5,717 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

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 Nh 31 over Stony Brook built?

It was built in 1928, making it 97 years old in 2025. It was reconstructed in 1985.

What condition is Nh 31 over Stony 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 April 2024.

How much traffic does Nh 31 over Stony Brook carry?

About 3,863 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is Nh 31 over Stony Brook?

The structure is 26 ft (7.9 m) long with a longest span of 23 ft (7 m) and a deck 40 ft wide.

Who owns Nh 31 over Stony Brook?

It is owned by the State Highway Agency.