US Bridges

FM 646 over Drainage Ditch

Fair

Galveston County, Texas · 0.50 MI W of FM 1266 · Structure no. 120850304901002

Built
1969
56 years old
Condition
Fair
inspected September 2024
Type
Culvert
Concrete
Length
38 ft
5 main spans
Daily traffic
18,730
2023 count
Owner
State
State Highway Agency

About this bridge

FM 646 over Drainage Ditch is a concrete culvert carrying FM 646 over Drainage Ditch in Galveston County, Texas. It was built in 1969, so it is 56 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 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 18,730 vehicles a day, roughly 5% of them trucks, projected to reach 13,730 by 2033. The structure is 38 ft (11.6 m) long and 86 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesFM 646
CrossesDrainage Ditch
Location0.50 MI W of FM 1266
RouteState Highway 646
CountyGalveston County
StateTexas
Coordinates29.49063, -95.05567
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
Channel and channel protection7 GoodSome minor problems.
Culvert5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionSeptember 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 geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating44 US tons
Inventory rating26 US tons

Structure

Structure typeCulvert
MaterialConcrete
DeckConcrete, cast-in-place
Main spans5
Design loadHS 20
Structure length38 ft (11.6 m)
Longest span7 ft (2.1 m)
Deck width86 ft (26.1 m)
Roadway width42 ft (12.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic18,730 (2023)
Projected traffic13,730 by 2033
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.9 mi (3 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 FM 646 over Drainage Ditch built?

It was built in 1969, making it 56 years old in 2025.

What condition is FM 646 over Drainage Ditch 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 FM 646 over Drainage Ditch carry?

About 18,730 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is FM 646 over Drainage Ditch?

The structure is 38 ft (11.6 m) long with a longest span of 7 ft (2.1 m) and a deck 86 ft wide.

Who owns FM 646 over Drainage Ditch?

It is owned by the State Highway Agency.