US Bridges

US 4 over Mill Brook

Fair

Grafton County, New Hampshire · 1.25 MI from Danbury Tl · Structure no. 009901760008600

Built
1948
77 years old
Condition
Fair
inspected May 2024
Type
Frame
Concrete
Length
27 ft
1 main span
Daily traffic
1,707
2023 count
Owner
State
State Highway Agency

About this bridge

US 4 over Mill Brook is a concrete frame carrying US 4 over Mill Brook in Grafton County, New Hampshire. It was built in 1948, so it is 77 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 1,707 vehicles a day, roughly 7% of them trucks, projected to reach 2,526 by 2043. The structure is 27 ft (8.2 m) long and 38 ft wide. If it were closed, the detour would be 8.1 mi (13 km).

Location

Open in Google Maps
CarriesUS 4
CrossesMill Brook
Location1.25 MI from Danbury Tl
RouteU.S. Route 4
CountyGrafton County
StateNew Hampshire
Coordinates43.56515, -71.92729
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionMay 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating89.5 US tons
Inventory rating43.7 US tons

Structure

Structure typeFrame
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadH 20
Structure length27 ft (8.2 m)
Longest span24 ft (7.3 m)
Deck width38 ft (11.5 m)
Roadway width32 ft (9.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,707 (2023)
Projected traffic2,526 by 2043
Trucks7%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.1 mi (13 km)
TollOn a free road
National Highway SystemNo
Strategic Highway NetworkInterstate STRAHNET route

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 US 4 over Mill Brook built?

It was built in 1948, making it 77 years old in 2025.

What condition is US 4 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 May 2024.

How much traffic does US 4 over Mill Brook carry?

About 1,707 vehicles per day (2023 count), of which roughly 7% are trucks.

How long is US 4 over Mill Brook?

The structure is 27 ft (8.2 m) long with a longest span of 24 ft (7.3 m) and a deck 38 ft wide.

Who owns US 4 over Mill Brook?

It is owned by the State Highway Agency.