US Bridges

Mill Road over Gridley River

Fair

Hillsborough County, New Hampshire · 0.5 MI from Jaffrey Tl · Structure no. 023500530006800

Built
1927
98 years old
Condition
Fair
inspected July 2024
Type
Slab
Concrete
Length
27 ft
2 main spans
Daily traffic
95
2023 count
Owner
City
City or Municipal Highway Agency

About this bridge

Mill Road over Gridley River is a concrete slab carrying Mill Road over Gridley River in Hillsborough County, New Hampshire. It was built in 1927, so it is 98 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 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 95 vehicles a day, roughly 4% of them trucks, projected to reach 140 by 2043. The structure is 27 ft (8.2 m) long and 19 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

Open in Google Maps
CarriesMill Road
CrossesGridley River
Location0.5 MI from Jaffrey Tl
CountyHillsborough County
StateNew Hampshire
Coordinates42.81424, -71.96986
Functional classRural Local

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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating32.6 US tons
Inventory rating23.1 US tons

Structure

Structure typeSlab
MaterialConcrete
DeckConcrete, cast-in-place
Main spans2
Design loadUnknown
Structure length27 ft (8.2 m)
Longest span9 ft (2.7 m)
Deck width19 ft (5.8 m)
Roadway width17 ft (5.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic95 (2023)
Projected traffic140 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 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 Mill Road over Gridley River built?

It was built in 1927, making it 98 years old in 2025.

What condition is Mill Road over Gridley 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 July 2024.

How much traffic does Mill Road over Gridley River carry?

About 95 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is Mill Road over Gridley River?

The structure is 27 ft (8.2 m) long with a longest span of 9 ft (2.7 m) and a deck 19 ft wide.

Who owns Mill Road over Gridley River?

It is owned by the City or Municipal Highway Agency.