US Bridges

M-21 over Swartz Creek

Fair

Genesee County, Michigan · In Flint · Structure no. 000000000002573

Built
1918
107 years old
Condition
Fair
inspected October 2024
Type
Arch - Deck
Concrete
Length
62 ft
1 main span
Daily traffic
12,900
2009 count
Owner
State
State Highway Agency

About this bridge

M-21 over Swartz Creek is a concrete arch - deck carrying M-21 over Swartz Creek in Genesee County, Michigan. It was built in 1918, so it is 107 years old, older than the Michigan average of 48.3 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 12,900 vehicles a day, roughly 2% of them trucks, projected to reach 19,050 by 2018. The structure is 62 ft (18.9 m) long and 62 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesM-21
CrossesSwartz Creek
LocationIn Flint
RouteState Highway 21
CountyGenesee County
StateMichigan
Coordinates43.00814, -83.69761
Functional classUrban Other Principal 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 inspectionOctober 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 adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating59.6 US tons
Inventory rating35.7 US tons

Structure

Structure typeArch - Deck
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length62 ft (18.9 m)
Longest span60 ft (18.2 m)
Deck width62 ft (19 m)
Roadway width50 ft (15.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic12,900 (2009)
Projected traffic19,050 by 2018
Trucks2%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusListed on the National Register of Historic Places
Work proposedDeck replacement with only incidental widening
Estimated improvement cost$21,000
NavigationNo navigation control on waterway

Frequently asked questions

When was M-21 over Swartz Creek built?

It was built in 1918, making it 107 years old in 2025.

What condition is M-21 over Swartz Creek 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 October 2024.

How much traffic does M-21 over Swartz Creek carry?

About 12,900 vehicles per day (2009 count), of which roughly 2% are trucks.

How long is M-21 over Swartz Creek?

The structure is 62 ft (18.9 m) long with a longest span of 60 ft (18.2 m) and a deck 62 ft wide.

Who owns M-21 over Swartz Creek?

It is owned by the State Highway Agency.