US Bridges

North L ST over Big Island Slough

Fair

Harris County, Texas · 0.5 MI E of Underwood RD · Structure no. 121020AA0103001

Built
1969
56 years old
Condition
Fair
inspected September 2023
Type
Stringer/Multi-beam or Girder
Concrete
Length
99 ft
3 main spans
Daily traffic
4,930
2009 count
Owner
County
County Highway Agency

About this bridge

North L ST over Big Island Slough is a concrete stringer/multi-beam or girder carrying North L ST over Big Island Slough in Harris 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 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 4,930 vehicles a day, projected to reach 5,000 by 2026. The structure is 99 ft (30.2 m) long and 34 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesNorth L ST
CrossesBig Island Slough
Location0.5 MI E of Underwood RD
RouteCounty Highway 0
CountyHarris County
StateTexas
Coordinates29.67998, -95.07917
Functional classUrban Local

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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionSeptember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating36 US tons
Inventory rating27 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialConcrete
DeckConcrete, cast-in-place
Main spans3
Design loadUnknown
Structure length99 ft (30.2 m)
Longest span33 ft (10.1 m)
Deck width34 ft (10.3 m)
Roadway width28 ft (8.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,930 (2009)
Projected traffic5,000 by 2026
Trucks0%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty 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 North L ST over Big Island Slough built?

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

What condition is North L ST over Big Island Slough 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 2023.

How much traffic does North L ST over Big Island Slough carry?

About 4,930 vehicles per day (2009 count).

How long is North L ST over Big Island Slough?

The structure is 99 ft (30.2 m) long with a longest span of 33 ft (10.1 m) and a deck 34 ft wide.

Who owns North L ST over Big Island Slough?

It is owned by the County Highway Agency.