US Bridges

Mn 48 over Grindstone River

Fair

Pine County, Minnesota · 2.2 MI E of JCT TH 35 · Structure no. 9819

Built
1964
61 years old
Condition
Fair
inspected July 2023
Type
Tee Beam
Concrete
Length
174 ft
3 main spans
Daily traffic
2,713
2022 count
Owner
State
State Highway Agency

About this bridge

Mn 48 over Grindstone River is a concrete tee beam carrying Mn 48 over Grindstone River in Pine County, Minnesota. It was built in 1964, so it is 61 years old, older than the Minnesota average of 38.5 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 2,713 vehicles a day, roughly 11% of them trucks, projected to reach 3,000 by 2042. The structure is 174 ft (53 m) long and 35 ft wide. If it were closed, the detour would be 19.9 mi (32 km).

Location

Open in Google Maps
CarriesMn 48
CrossesGrindstone River
Location2.2 MI E of JCT TH 35
RouteState Highway 48
CountyPine County
StateMinnesota
Coordinates46.01094, -92.88726
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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
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 alignment5: Somewhat better than minimum adequacy to tolerate being left in place as is
Operating rating70 US tons
Inventory rating41.9 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length174 ft (53 m)
Longest span58 ft (17.7 m)
Deck width35 ft (10.8 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,713 (2022)
Projected traffic3,000 by 2042
Trucks11%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed19.9 mi (32 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost$603 million
NavigationNo navigation control on waterway

Frequently asked questions

When was Mn 48 over Grindstone River built?

It was built in 1964, making it 61 years old in 2025.

What condition is Mn 48 over Grindstone 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 2023.

How much traffic does Mn 48 over Grindstone River carry?

About 2,713 vehicles per day (2022 count), of which roughly 11% are trucks.

How long is Mn 48 over Grindstone River?

The structure is 174 ft (53 m) long with a longest span of 58 ft (17.7 m) and a deck 35 ft wide.

Who owns Mn 48 over Grindstone River?

It is owned by the State Highway Agency.