US Bridges

SH 105 over Alligator Crk

Fair

Montgomery County, Texas · 0.2 MI E of IH 45 · Structure no. 121700033803075

Built
1947
78 years old, rebuilt 1990
Condition
Fair
inspected September 2024
Type
Slab
Concrete
Length
100 ft
5 main spans
Daily traffic
27,758
2023 count
Owner
State
State Highway Agency

About this bridge

SH 105 over Alligator Crk is a concrete slab carrying SH 105 over Alligator Crk in Montgomery County, Texas. It was built in 1947 and reconstructed in 1990, so it is 78 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 27,758 vehicles a day, roughly 4% of them trucks, projected to reach 44,413 by 2042. The structure is 100 ft (30.5 m) long and 114 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesSH 105
CrossesAlligator Crk
Location0.2 MI E of IH 45
RouteState Highway 105
CountyMontgomery County
StateTexas
Coordinates30.31388, -95.46916
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionSeptember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour evaluation has not been made
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating58 US tons
Inventory rating34.9 US tons

Structure

Structure typeSlab
MaterialConcrete
DeckConcrete, cast-in-place
Main spans5
Design loadH 20
Structure length100 ft (30.5 m)
Longest span20 ft (6.1 m)
Deck width114 ft (34.7 m)
Roadway width86 ft (26.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic27,758 (2023)
Projected traffic44,413 by 2042
Trucks4%
Lanes on structure7
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 statusPossibly eligible for the National Register; requires further investigation
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was SH 105 over Alligator Crk built?

It was built in 1947, making it 78 years old in 2025. It was reconstructed in 1990.

What condition is SH 105 over Alligator Crk 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 September 2024.

How much traffic does SH 105 over Alligator Crk carry?

About 27,758 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is SH 105 over Alligator Crk?

The structure is 100 ft (30.5 m) long with a longest span of 20 ft (6.1 m) and a deck 114 ft wide.

Who owns SH 105 over Alligator Crk?

It is owned by the State Highway Agency.