US Bridges

I-93 over Black Brook

Fair

Grafton County, New Hampshire · 2.8 MI Sugarhill Tl · Structure no. 008700890010700

Built
1959
66 years old, rebuilt 1972
Condition
Fair
inspected May 2023
Type
Culvert
Concrete
Length
30 ft
1 main span
Daily traffic
5,250
2023 count
Owner
State
State Highway Agency

About this bridge

I-93 over Black Brook is a concrete culvert carrying I-93 over Black Brook in Grafton County, New Hampshire. It was built in 1959 and reconstructed in 1972, so it is 66 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 5,250 vehicles a day, roughly 9% of them trucks, projected to reach 7,770 by 2043. The structure is 30 ft (9.1 m) long. If it were closed, the detour would be 6.2 mi (10 km).

Location

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CarriesI-93
CrossesBlack Brook
Location2.8 MI Sugarhill Tl
RouteInterstate 93
CountyGrafton County
StateNew Hampshire
Coordinates44.20766, -71.71871
Functional classRural Principal Arterial - Interstate

Condition and inspection

Fair

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

ComponentRatingMeaning
Channel and channel protection7 GoodSome minor problems.
Culvert6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMay 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating99 US tons
Inventory rating99 US tons

Structure

Structure typeCulvert
MaterialConcrete
DeckNot applicable
Main spans1
Design loadHS 20 + Mod
Structure length30 ft (9.1 m)
Longest span30 ft (9.1 m)
Deck width0 ft (0 m)
Roadway width0 ft (0 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic5,250 (2023)
Projected traffic7,770 by 2043
Trucks9%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.2 mi (10 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible 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 I-93 over Black Brook built?

It was built in 1959, making it 66 years old in 2025. It was reconstructed in 1972.

What condition is I-93 over Black 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 May 2023.

How much traffic does I-93 over Black Brook carry?

About 5,250 vehicles per day (2023 count), of which roughly 9% are trucks.

How long is I-93 over Black Brook?

The structure is 30 ft (9.1 m) long with a longest span of 30 ft (9.1 m).

Who owns I-93 over Black Brook?

It is owned by the State Highway Agency.