US Bridges

Colby Road over Piscataquog River

Good

Hillsborough County, New Hampshire · 0.17 MI River Road · Structure no. 026701640005200

Built
1962
63 years old
Condition
Good
inspected August 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
57 ft
1 main span
Daily traffic
682
2023 count
Owner
City
City or Municipal Highway Agency

About this bridge

Colby Road over Piscataquog River is a steel stringer/multi-beam or girder carrying Colby Road over Piscataquog River in Hillsborough County, New Hampshire. It was built in 1962, so it is 63 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 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 682 vehicles a day, roughly 4% of them trucks, projected to reach 1,009 by 2043. The structure is 57 ft (17.4 m) long and 21 ft wide. If it were closed, the detour would be 6.2 mi (10 km).

Location

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CarriesColby Road
CrossesPiscataquog River
Location0.17 MI River Road
CountyHillsborough County
StateNew Hampshire
Coordinates43.05151, -71.65413
Functional classRural Local

Condition and inspection

Good

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

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionAugust 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 rating42.8 US tons
Inventory rating25.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length57 ft (17.4 m)
Longest span52 ft (15.8 m)
Deck width21 ft (6.4 m)
Roadway width18 ft (5.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic682 (2023)
Projected traffic1,009 by 2043
Trucks4%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.2 mi (10 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 Colby Road over Piscataquog River built?

It was built in 1962, making it 63 years old in 2025.

What condition is Colby Road over Piscataquog River 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 2023.

How much traffic does Colby Road over Piscataquog River carry?

About 682 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is Colby Road over Piscataquog River?

The structure is 57 ft (17.4 m) long with a longest span of 52 ft (15.8 m) and a deck 21 ft wide.

Who owns Colby Road over Piscataquog River?

It is owned by the City or Municipal Highway Agency.