US Bridges

Mira-Myrtis RD over Black Bayou Lake

Fair

Caddo Parish, Louisiana · 1 Mi. E of La. HWY 1 · Structure no. 040932559935881

Built
1978
47 years old
Condition
Fair
inspected February 2025
Type
Slab
Concrete
Length
305 ft
16 main spans
Daily traffic
305
2019 count
Owner
County
County Highway Agency

About this bridge

Mira-Myrtis RD over Black Bayou Lake is a concrete slab carrying Mira-Myrtis RD over Black Bayou Lake in Caddo Parish, Louisiana. It was built in 1978, so it is 47 years old, older than the Louisiana average of 43 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 305 vehicles a day, projected to reach 335 by 2039. The structure is 305 ft (93 m) long and 31 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

Open in Google Maps
CarriesMira-Myrtis RD
CrossesBlack Bayou Lake
Location1 Mi. E of La. HWY 1
RouteCounty Highway 0
CountyCaddo Parish
StateLouisiana
Coordinates32.93229, -93.98046
Functional classRural 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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionFebruary 2025
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating33.2 US tons
Inventory rating25.7 US tons

Structure

Structure typeSlab
MaterialConcrete
DeckConcrete, precast panels
Main spans16
Design loadHS 20
Structure length305 ft (93 m)
Longest span19 ft (5.8 m)
Deck width31 ft (9.5 m)
Roadway width28 ft (8.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic305 (2019)
Projected traffic335 by 2039
Trucks—
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.7 mi (6 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty 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 Mira-Myrtis RD over Black Bayou Lake built?

It was built in 1978, making it 47 years old in 2025.

What condition is Mira-Myrtis RD over Black Bayou Lake 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 February 2025.

How much traffic does Mira-Myrtis RD over Black Bayou Lake carry?

About 305 vehicles per day (2019 count).

How long is Mira-Myrtis RD over Black Bayou Lake?

The structure is 305 ft (93 m) long with a longest span of 19 ft (5.8 m) and a deck 31 ft wide.

Who owns Mira-Myrtis RD over Black Bayou Lake?

It is owned by the County Highway Agency.