US Bridges

I-93 NB over Bog Brook

Good

Grafton County, New Hampshire · 1.1 MI from Plymouth Tl · Structure no. 003501050005800

Built
1963
62 years old, rebuilt 1992
Condition
Good
inspected July 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
152 ft
3 main spans
Daily traffic
10,585
2023 count
Owner
State
State Highway Agency

About this bridge

I-93 NB over Bog Brook is a steel continuous stringer/multi-beam or girder carrying I-93 NB over Bog Brook in Grafton County, New Hampshire. It was built in 1963 and reconstructed in 1992, so it is 62 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 good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 10,585 vehicles a day, roughly 9% of them trucks, projected to reach 15,665 by 2043. The structure is 152 ft (46.3 m) long and 50 ft wide. If it were closed, the detour would be 6.2 mi (10 km).

Location

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CarriesI-93 NB
CrossesBog Brook
Location1.1 MI from Plymouth Tl
RouteInterstate 93
CountyGrafton County
StateNew Hampshire
Coordinates43.79821, -71.67655
Functional classRural Principal Arterial - Interstate

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
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 evaluation7: Better than present minimum criteria
Deck geometry9: Superior to present desirable criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating93.8 US tons
Inventory rating56.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20 + Mod
Structure length152 ft (46.3 m)
Longest span57 ft (17.4 m)
Deck width50 ft (15.1 m)
Roadway width46 ft (14 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic10,585 (2023)
Projected traffic15,665 by 2043
Trucks9%
Lanes on structure2
Traffic directionOne-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 NB over Bog Brook built?

It was built in 1963, making it 62 years old in 2025. It was reconstructed in 1992.

What condition is I-93 NB over Bog Brook in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in July 2023.

How much traffic does I-93 NB over Bog Brook carry?

About 10,585 vehicles per day (2023 count), of which roughly 9% are trucks.

How long is I-93 NB over Bog Brook?

The structure is 152 ft (46.3 m) long with a longest span of 57 ft (17.4 m) and a deck 50 ft wide.

Who owns I-93 NB over Bog Brook?

It is owned by the State Highway Agency.