US Bridges

Boston Post Road over Souhegan River

Fair

Hillsborough County, New Hampshire · 1.9 MI Merrimack Tl · Structure no. 000701930013000

Built
1977
48 years old
Condition
Fair
inspected June 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
88 ft
1 main span
Daily traffic
4,409
2023 count
Owner
City
City or Municipal Highway Agency

About this bridge

Boston Post Road over Souhegan River is a steel stringer/multi-beam or girder carrying Boston Post Road over Souhegan River in Hillsborough County, New Hampshire. It was built in 1977, so it is 48 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 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 4,409 vehicles a day, roughly 4% of them trucks, projected to reach 6,525 by 2043. The structure is 88 ft (26.8 m) long and 31 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

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CarriesBoston Post Road
CrossesSouhegan River
Location1.9 MI Merrimack Tl
CountyHillsborough County
StateNew Hampshire
Coordinates42.82725, -71.58524
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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJune 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating50.4 US tons
Inventory rating36 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadUnknown
Structure length88 ft (26.8 m)
Longest span83 ft (25.3 m)
Deck width31 ft (9.4 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,409 (2023)
Projected traffic6,525 by 2043
Trucks4%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed3.7 mi (6 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCity or Municipal Highway Agency
Maintained byCity or Municipal 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 Boston Post Road over Souhegan River built?

It was built in 1977, making it 48 years old in 2025.

What condition is Boston Post Road over Souhegan 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 June 2023.

How much traffic does Boston Post Road over Souhegan River carry?

About 4,409 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is Boston Post Road over Souhegan River?

The structure is 88 ft (26.8 m) long with a longest span of 83 ft (25.3 m) and a deck 31 ft wide.

Who owns Boston Post Road over Souhegan River?

It is owned by the City or Municipal Highway Agency.