US Bridges

Comstock Road over Black River

Fair

St. Clair County, Michigan · Sec 17 Grant Twp · Structure no. 000000000010077

Built
1996
29 years old
Condition
Fair
inspected December 2024
Type
Box Beam or Girders - Multiple
Prestressed Concrete
Length
243 ft
3 main spans
Daily traffic
1,025
1994 count
Owner
County
County Highway Agency

About this bridge

Comstock Road over Black River is a prestressed concrete box beam or girders - multiple carrying Comstock Road over Black River in St. Clair County, Michigan. It was built in 1996, so it is 29 years old, younger 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 1,025 vehicles a day, roughly 3% of them trucks, projected to reach 1,525 by 2014. The structure is 243 ft (74 m) long and 37 ft wide. If it were closed, the detour would be 5 mi (8 km).

Location

Open in Google Maps
CarriesComstock Road
CrossesBlack River
LocationSec 17 Grant Twp
RouteCounty Highway 7794
CountySt. Clair County
StateMichigan
Coordinates43.12289, -82.61672
Functional classRural Major Collector

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.
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 protection7 GoodSome minor problems.
Last inspectionDecember 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 geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating107.1 US tons
Inventory rating67.9 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length243 ft (74 m)
Longest span81 ft (24.7 m)
Deck width37 ft (11.4 m)
Roadway width35 ft (10.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,025 (1994)
Projected traffic1,525 by 2014
Trucks3%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed5 mi (8 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusListed on the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Comstock Road over Black River built?

It was built in 1996, making it 29 years old in 2025.

What condition is Comstock Road over Black 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 December 2024.

How much traffic does Comstock Road over Black River carry?

About 1,025 vehicles per day (1994 count), of which roughly 3% are trucks.

How long is Comstock Road over Black River?

The structure is 243 ft (74 m) long with a longest span of 81 ft (24.7 m) and a deck 37 ft wide.

Who owns Comstock Road over Black River?

It is owned by the County Highway Agency.