US Bridges

21st Avenue over Little Mcpherson Bayou

Fair

Pinellas County, Florida · Pass-A-Grille Way · Structure no. 157501

Built
1954
71 years old, rebuilt 1980
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
290 ft
6 main spans
Daily traffic
3,046
2023 count
Owner
City
City or Municipal Highway Agency

About this bridge

21st Avenue over Little Mcpherson Bayou is a prestressed concrete stringer/multi-beam or girder carrying 21st Avenue over Little Mcpherson Bayou in Pinellas County, Florida. It was built in 1954 and reconstructed in 1980, so it is 71 years old, older than the Florida average of 41.3 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 3,046 vehicles a day, roughly 2% of them trucks, projected to reach 5,285 by 2042. The structure is 290 ft (88.5 m) long and 37 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

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Carries21st Avenue
CrossesLittle Mcpherson Bayou
LocationPass-A-Grille Way
RouteCity Street 0
CountyPinellas County
StateFlorida
Coordinates27.6972, -82.73489
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation6: Equal to present minimum criteria
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment5: Somewhat better than minimum adequacy to tolerate being left in place as is
Operating rating59.1 US tons
Inventory rating35.5 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans6
Design loadUnknown
Structure length290 ft (88.5 m)
Longest span48 ft (14.6 m)
Deck width37 ft (11.4 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,046 (2023)
Projected traffic5,285 by 2042
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed123.7 mi (199 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCity or Municipal Highway Agency
Maintained byCity or Municipal Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was 21st Avenue over Little Mcpherson Bayou built?

It was built in 1954, making it 71 years old in 2025. It was reconstructed in 1980.

What condition is 21st Avenue over Little Mcpherson Bayou 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 July 2023.

How much traffic does 21st Avenue over Little Mcpherson Bayou carry?

About 3,046 vehicles per day (2023 count), of which roughly 2% are trucks.

How long is 21st Avenue over Little Mcpherson Bayou?

The structure is 290 ft (88.5 m) long with a longest span of 48 ft (14.6 m) and a deck 37 ft wide.

Who owns 21st Avenue over Little Mcpherson Bayou?

It is owned by the City or Municipal Highway Agency.