US Bridges

Dorchester Road over Grant Brook

Fair

Grafton County, New Hampshire · 1.0 MI JCT Route 10 · Structure no. 015700960010000

Built
1940
85 years old, rebuilt 1984
Condition
Fair
inspected March 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
45 ft
1 main span
Daily traffic
1,132
2023 count
Owner
State
State Highway Agency

About this bridge

Dorchester Road over Grant Brook is a steel stringer/multi-beam or girder carrying Dorchester Road over Grant Brook in Grafton County, New Hampshire. It was built in 1940 and reconstructed in 1984, so it is 85 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 1,132 vehicles a day, roughly 10% of them trucks, projected to reach 1,675 by 2043. The structure is 45 ft (13.7 m) long and 28 ft wide. If it were closed, the detour would be 6.8 mi (11 km).

Location

Open in Google Maps
CarriesDorchester Road
CrossesGrant Brook
Location1.0 MI JCT Route 10
RouteState Highway 0
CountyGrafton County
StateNew Hampshire
Coordinates43.8034, -72.14332
Functional classRural Minor Collector

Condition and inspection

Fair

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

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMarch 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating53 US tons
Inventory rating31 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadH 10
Structure length45 ft (13.7 m)
Longest span40 ft (12.2 m)
Deck width28 ft (8.6 m)
Roadway width25 ft (7.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,132 (2023)
Projected traffic1,675 by 2043
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.8 mi (11 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusPossibly eligible for the National Register; requires further investigation
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 Dorchester Road over Grant Brook built?

It was built in 1940, making it 85 years old in 2025. It was reconstructed in 1984.

What condition is Dorchester Road over Grant 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 March 2024.

How much traffic does Dorchester Road over Grant Brook carry?

About 1,132 vehicles per day (2023 count), of which roughly 10% are trucks.

How long is Dorchester Road over Grant Brook?

The structure is 45 ft (13.7 m) long with a longest span of 40 ft (12.2 m) and a deck 28 ft wide.

Who owns Dorchester Road over Grant Brook?

It is owned by the State Highway Agency.