US Bridges

Mn 18 over Snake River

Poor

Aitkin County, Minnesota · 1.8 MI E of JCT TH 65 · Structure no. 9004

Built
1955
70 years old
Condition
Poor
inspected September 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
128 ft
3 main spans
Daily traffic
629
2022 count
Owner
State
State Highway Agency

About this bridge

Mn 18 over Snake River is a steel stringer/multi-beam or girder carrying Mn 18 over Snake River in Aitkin County, Minnesota. It was built in 1955, so it is 70 years old, older than the Minnesota average of 38.5 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 629 vehicles a day, roughly 9% of them trucks, projected to reach 630 by 2042. The structure is 128 ft (39 m) long and 34 ft wide. If it were closed, the detour would be 13 mi (21 km).

Location

Open in Google Maps
CarriesMn 18
CrossesSnake River
Location1.8 MI E of JCT TH 65
RouteState Highway 18
CountyAitkin County
StateMinnesota
Coordinates46.21702, -93.2408
Functional classRural Minor Arterial

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionSeptember 2024
Inspection intervalevery 12 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating83.9 US tons
Inventory rating50.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans3
Design loadH 20
Structure length128 ft (39 m)
Longest span43 ft (13 m)
Deck width34 ft (10.5 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic629 (2022)
Projected traffic630 by 2042
Trucks9%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed13 mi (21 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$412 million
NavigationNo navigation control on waterway

Frequently asked questions

When was Mn 18 over Snake River built?

It was built in 1955, making it 70 years old in 2025.

What condition is Mn 18 over Snake River in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in September 2024.

How much traffic does Mn 18 over Snake River carry?

About 629 vehicles per day (2022 count), of which roughly 9% are trucks.

How long is Mn 18 over Snake River?

The structure is 128 ft (39 m) long with a longest span of 43 ft (13 m) and a deck 34 ft wide.

Who owns Mn 18 over Snake River?

It is owned by the State Highway Agency.