US Bridges

Thornton Road over Pennichuck Brook

Good

Hillsborough County, New Hampshire · Nashua/Merr Tl · Structure no. 016800890003800

Built
2001
24 years old
Condition
Good
inspected August 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
47 ft
1 main span
Daily traffic
1,231
2023 count
Owner
City
City or Municipal Highway Agency

About this bridge

Thornton Road over Pennichuck Brook is a steel stringer/multi-beam or girder carrying Thornton Road over Pennichuck Brook in Hillsborough County, New Hampshire. It was built in 2001, so it is 24 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 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 1,231 vehicles a day, roughly 4% of them trucks, projected to reach 1,821 by 2043. The structure is 47 ft (14.2 m) long and 34 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

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CarriesThornton Road
CrossesPennichuck Brook
LocationNashua/Merr Tl
RouteCity Street 0
CountyHillsborough County
StateNew Hampshire
Coordinates42.80044, -71.51587
Functional classUrban Collector

Condition and inspection

Good

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

ComponentRatingMeaning
Deck8 Very GoodNo problems noted.
Superstructure8 Very GoodNo problems noted.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than 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 alignment4: Meets minimum tolerable limits to be left in place as is
Operating rating86.4 US tons
Inventory rating51.8 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, precast panels
Main spans1
Design loadHS 25 or greater
Structure length47 ft (14.2 m)
Longest span42 ft (12.7 m)
Deck width34 ft (10.5 m)
Roadway width26 ft (7.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,231 (2023)
Projected traffic1,821 by 2043
Trucks4%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
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 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 Thornton Road over Pennichuck Brook built?

It was built in 2001, making it 24 years old in 2025.

What condition is Thornton Road over Pennichuck 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 August 2024.

How much traffic does Thornton Road over Pennichuck Brook carry?

About 1,231 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is Thornton Road over Pennichuck Brook?

The structure is 47 ft (14.2 m) long with a longest span of 42 ft (12.7 m) and a deck 34 ft wide.

Who owns Thornton Road over Pennichuck Brook?

It is owned by the City or Municipal Highway Agency.