US Bridges

Nh 31 over Stony Brook

Fair

Hillsborough County, New Hampshire · 0.4 MI from JCT RTE 101 · Structure no. 027701320012700

Built
1905
120 years old
Condition
Fair
inspected April 2024
Type
Arch - Deck
Masonry
Length
57 ft
1 main span
Daily traffic
2,883
2023 count
Owner
State
State Highway Agency

About this bridge

Nh 31 over Stony Brook is a masonry arch - deck carrying Nh 31 over Stony Brook in Hillsborough County, New Hampshire. It was built in 1905, so it is 120 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 2,883 vehicles a day, roughly 4% of them trucks, projected to reach 4,266 by 2043. The structure is 57 ft (17.4 m) long and 30 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
CarriesNh 31
CrossesStony Brook
Location0.4 MI from JCT RTE 101
RouteState Highway 31
CountyHillsborough County
StateNew Hampshire
Coordinates42.84454, -71.73886
Functional classUrban Minor Arterial

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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
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 evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment4: Meets minimum tolerable limits to be left in place as is
Operating rating36.2 US tons
Inventory rating21.8 US tons

Structure

Structure typeArch - Deck
MaterialMasonry
DeckNot applicable
Main spans1
Design loadUnknown
Structure length57 ft (17.4 m)
Longest span50 ft (15.2 m)
Deck width30 ft (9.1 m)
Roadway width23 ft (7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,883 (2023)
Projected traffic4,266 by 2043
Trucks4%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed3.1 mi (5 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusEligible for the National Register of Historic Places
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 1905, making it 120 years old in 2025.

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 2,883 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is Nh 31 over Stony Brook?

The structure is 57 ft (17.4 m) long with a longest span of 50 ft (15.2 m) and a deck 30 ft wide.

Who owns Nh 31 over Stony Brook?

It is owned by the State Highway Agency.