US Bridges

I-89 SB over Bog Road

Fair

Merrimack County, New Hampshire · 1.4 MI Fromsutton Tl · Structure no. 018801030006400

Built
1967
58 years old, rebuilt 1989
Condition
Fair
inspected April 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
185 ft
3 main spans
Daily traffic
9,810
2023 count
Owner
State
State Highway Agency

About this bridge

I-89 SB over Bog Road is a steel continuous stringer/multi-beam or girder carrying I-89 SB over Bog Road in Merrimack County, New Hampshire. It was built in 1967 and reconstructed in 1989, so it is 58 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 9,810 vehicles a day, roughly 9% of them trucks, projected to reach 14,518 by 2043. The structure is 185 ft (56.4 m) long and 44 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-89 SB
CrossesBog Road
Location1.4 MI Fromsutton Tl
RouteInterstate 89
CountyMerrimack County
StateNew Hampshire
Coordinates43.39553, -72.00423
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.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionApril 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating87.1 US tons
Inventory rating52.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20 + Mod
Structure length185 ft (56.4 m)
Longest span69 ft (21 m)
Deck width44 ft (13.4 m)
Roadway width39 ft (11.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic9,810 (2023)
Projected traffic14,518 by 2043
Trucks9%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed1.2 mi (2 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)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-89 SB over Bog Road built?

It was built in 1967, making it 58 years old in 2025. It was reconstructed in 1989.

What condition is I-89 SB over Bog Road 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 2023.

How much traffic does I-89 SB over Bog Road carry?

About 9,810 vehicles per day (2023 count), of which roughly 9% are trucks.

How long is I-89 SB over Bog Road?

The structure is 185 ft (56.4 m) long with a longest span of 69 ft (21 m) and a deck 44 ft wide.

Who owns I-89 SB over Bog Road?

It is owned by the State Highway Agency.