US Bridges

Nh 12 over Mill Brook

Fair

Cheshire County, New Hampshire · 3.5 MI to Walpole Tl · Structure no. 027201450013100

Built
1928
97 years old, rebuilt 2013
Condition
Fair
inspected June 2024
Type
Slab
Concrete
Length
37 ft
2 main spans
Daily traffic
6,478
2023 count
Owner
State
State Highway Agency

About this bridge

Nh 12 over Mill Brook is a concrete slab carrying Nh 12 over Mill Brook in Cheshire County, New Hampshire. It was built in 1928 and reconstructed in 2013, so it is 97 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 6,478 vehicles a day, roughly 7% of them trucks, projected to reach 9,587 by 2043. The structure is 37 ft (11.3 m) long and 34 ft wide. If it were closed, the detour would be 6.8 mi (11 km).

Location

Open in Google Maps
CarriesNh 12
CrossesMill Brook
Location3.5 MI to Walpole Tl
RouteState Highway 12
CountyCheshire County
StateNew Hampshire
Coordinates42.99587, -72.40981
Functional classRural Minor Arterial

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 protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJune 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 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 rating67.1 US tons
Inventory rating51.8 US tons

Structure

Structure typeSlab
MaterialConcrete
DeckConcrete, cast-in-place
Main spans2
Design loadHL 93
Structure length37 ft (11.3 m)
Longest span15 ft (4.6 m)
Deck width34 ft (10.5 m)
Roadway width32 ft (9.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic6,478 (2023)
Projected traffic9,587 by 2043
Trucks7%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.8 mi (11 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState 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 Nh 12 over Mill Brook built?

It was built in 1928, making it 97 years old in 2025. It was reconstructed in 2013.

What condition is Nh 12 over Mill 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 June 2024.

How much traffic does Nh 12 over Mill Brook carry?

About 6,478 vehicles per day (2023 count), of which roughly 7% are trucks.

How long is Nh 12 over Mill Brook?

The structure is 37 ft (11.3 m) long with a longest span of 15 ft (4.6 m) and a deck 34 ft wide.

Who owns Nh 12 over Mill Brook?

It is owned by the State Highway Agency.