US Bridges

FM 646 over Highland Bayou

Good

Galveston County, Texas · 0.55 MI N of SH 6 · Structure no. 120850097801007

Built
2006
19 years old
Condition
Good
inspected October 2024
Type
Culvert
Concrete
Length
33 ft
3 main spans
Daily traffic
9,853
2020 count
Owner
State
State Highway Agency

About this bridge

FM 646 over Highland Bayou is a concrete culvert carrying FM 646 over Highland Bayou in Galveston County, Texas. It was built in 2006, so it is 19 years old, younger than the Texas average of 44.4 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 9,853 vehicles a day, roughly 6% of them trucks, projected to reach 11,190 by 2033. The structure is 33 ft (10.1 m) long and 130 ft wide. If it were closed, the detour would be 6.2 mi (10 km).

Location

Open in Google Maps
CarriesFM 646
CrossesHighland Bayou
Location0.55 MI N of SH 6
RouteState Highway 646
CountyGalveston County
StateTexas
Coordinates29.3807, -95.08947
Functional classUrban Other Principal Arterial

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Channel and channel protection8 Very GoodNo problems noted.
Culvert7 GoodSome minor problems.
Last inspectionOctober 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 geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating44.6 US tons
Inventory rating26.6 US tons

Structure

Structure typeCulvert
MaterialConcrete
DeckNot applicable
Main spans3
Design loadHS 20
Structure length33 ft (10.1 m)
Longest span9 ft (2.7 m)
Deck width130 ft (39.7 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic9,853 (2020)
Projected traffic11,190 by 2033
Trucks6%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.2 mi (10 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was FM 646 over Highland Bayou built?

It was built in 2006, making it 19 years old in 2025.

What condition is FM 646 over Highland Bayou in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in October 2024.

How much traffic does FM 646 over Highland Bayou carry?

About 9,853 vehicles per day (2020 count), of which roughly 6% are trucks.

How long is FM 646 over Highland Bayou?

The structure is 33 ft (10.1 m) long with a longest span of 9 ft (2.7 m) and a deck 130 ft wide.

Who owns FM 646 over Highland Bayou?

It is owned by the State Highway Agency.