US Bridges

East Dunbarton RD over Black Brook

Fair

Hillsborough County, New Hampshire · Town RD · Structure no. 009501730013300

Built
1994
31 years old
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
48 ft
1 main span
Daily traffic
1,591
2023 count
Owner
City
City or Municipal Highway Agency

About this bridge

East Dunbarton RD over Black Brook is a steel stringer/multi-beam or girder carrying East Dunbarton RD over Black Brook in Hillsborough County, New Hampshire. It was built in 1994, so it is 31 years old, younger 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 1,591 vehicles a day, roughly 4% of them trucks, projected to reach 2,354 by 2043. The structure is 48 ft (14.6 m) long and 24 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesEast Dunbarton RD
CrossesBlack Brook
LocationTown RD
CountyHillsborough County
StateNew Hampshire
Coordinates43.03645, -71.5116
Functional classUrban 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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
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 adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating70.7 US tons
Inventory rating42.5 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckCorrugated steel
Main spans1
Design loadHS 25 or greater
Structure length48 ft (14.6 m)
Longest span43 ft (13.1 m)
Deck width24 ft (7.3 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,591 (2023)
Projected traffic2,354 by 2043
Trucks4%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCity or Municipal Highway Agency
Maintained byCity or Municipal 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 East Dunbarton RD over Black Brook built?

It was built in 1994, making it 31 years old in 2025.

What condition is East Dunbarton RD 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 July 2023.

How much traffic does East Dunbarton RD over Black Brook carry?

About 1,591 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is East Dunbarton RD over Black Brook?

The structure is 48 ft (14.6 m) long with a longest span of 43 ft (13.1 m) and a deck 24 ft wide.

Who owns East Dunbarton RD over Black Brook?

It is owned by the City or Municipal Highway Agency.