US Bridges

I-93 SB over Ammonoosuc River

Fair

Grafton County, New Hampshire · 2.1 MI Bethlehem Tl · Structure no. 015301870006000

Built
1960
65 years old, rebuilt 1982
Condition
Fair
inspected July 2023
Type
Girder and Floorbeam System
Steel
Length
282 ft
1 main span
Daily traffic
4,499
2023 count
Owner
State
State Highway Agency

About this bridge

I-93 SB over Ammonoosuc River is a steel girder and floorbeam system carrying I-93 SB over Ammonoosuc River in Grafton County, New Hampshire. It was built in 1960 and reconstructed in 1982, so it is 65 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 4,499 vehicles a day, roughly 9% of them trucks, projected to reach 6,658 by 2043. The structure is 282 ft (86 m) long and 51 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

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CarriesI-93 SB
CrossesAmmonoosuc River
Location2.1 MI Bethlehem Tl
RouteInterstate 93
CountyGrafton County
StateNew Hampshire
Coordinates44.30459, -71.79675
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
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 adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating57.1 US tons
Inventory rating34.2 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+2 approach)
Design loadHS 20 + Mod
Structure length282 ft (86 m)
Longest span145 ft (44.2 m)
Deck width51 ft (15.5 m)
Roadway width47 ft (14.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,499 (2023)
Projected traffic6,658 by 2043
Trucks9%
Lanes on structure3
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.7 mi (6 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 SB over Ammonoosuc River built?

It was built in 1960, making it 65 years old in 2025. It was reconstructed in 1982.

What condition is I-93 SB over Ammonoosuc River 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 July 2023.

How much traffic does I-93 SB over Ammonoosuc River carry?

About 4,499 vehicles per day (2023 count), of which roughly 9% are trucks.

How long is I-93 SB over Ammonoosuc River?

The structure is 282 ft (86 m) long with a longest span of 145 ft (44.2 m) and a deck 51 ft wide.

Who owns I-93 SB over Ammonoosuc River?

It is owned by the State Highway Agency.