US Bridges

FM 81 over San Antonio River

Fair

Karnes County, Texas · 0.6 MI E of US 181 · Structure no. 161290112301001

Built
1949
76 years old
Condition
Fair
inspected June 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
471 ft
3 main spans
Daily traffic
433
2024 count
Owner
State
State Highway Agency

About this bridge

FM 81 over San Antonio River is a steel continuous stringer/multi-beam or girder carrying FM 81 over San Antonio River in Karnes County, Texas. It was built in 1949, so it is 76 years old, older than the Texas average of 44.4 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 6 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 433 vehicles a day, roughly 61% of them trucks, projected to reach 556 by 2042. The structure is 471 ft (143.6 m) long and 26 ft wide. If it were closed, the detour would be 6.8 mi (11 km).

Location

Open in Google Maps
CarriesFM 81
CrossesSan Antonio River
Location0.6 MI E of US 181
RouteState Highway 81
CountyKarnes County
StateTexas
Coordinates28.95485, -97.97738
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionJune 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment5: Somewhat better than minimum adequacy to tolerate being left in place as is
Operating rating44 US tons
Inventory rating26 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3 (+6 approach)
Design loadOther
Structure length471 ft (143.6 m)
Longest span90 ft (27.4 m)
Deck width26 ft (7.8 m)
Roadway width24 ft (7.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic433 (2024)
Projected traffic556 by 2042
Trucks61%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.8 mi (11 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedOther structural work, including hydraulic replacements
Estimated improvement cost$29,000
NavigationNo navigation control on waterway

Frequently asked questions

When was FM 81 over San Antonio River built?

It was built in 1949, making it 76 years old in 2025.

What condition is FM 81 over San Antonio 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 June 2024.

How much traffic does FM 81 over San Antonio River carry?

About 433 vehicles per day (2024 count), of which roughly 61% are trucks.

How long is FM 81 over San Antonio River?

The structure is 471 ft (143.6 m) long with a longest span of 90 ft (27.4 m) and a deck 26 ft wide.

Who owns FM 81 over San Antonio River?

It is owned by the State Highway Agency.