According to FDOT’s Broward district office, bridges receive a “structurally deficient” rating when one or more major features score below 4 on a scale of 1 to 9. A bridge with a rating of 4 is considered “poor,” and becomes eligible for funds to replace it, John Danielsen of FDOT’s Broward district office wrote in an email.

The principal sources of repair financing are state and federal transportation grants as well as municipal road funds, much of that generated by gasoline taxes, though some local governments also issue bonds, take out bank loans or tap into road impact fees paid by developers.

Yet highway and public works officials say the economic downturn led to tightened maintenance budgets and reduced gas-tax receipts as people drove less. FDOT’s Pego and other officials warn that rising efficiency standards for automobiles, as well as decisions by more people to drive less because of high gas prices, could lead to a permanent drop in fuel-tax revenue in the near future.

The tax is set at 52.4 cents per gallon, so revenue doesn’t rise along with gas prices.

That leaves public works officials guessing about how much money will be available for major repairs or bridge replacements in coming years.

“It is a fairly tight situation now, especially with the economy having gone downhill,” said Miami-Dade’s acting chief engineer, Antonio Cotarelo. “We really don’t know where this is going. Some of the most important repairs, we try to anticipate and prioritize.”

Some of the major bridges rated as structurally deficient are already scheduled and funded for repair work, including Bear Cut. The Miami-Dade County Commission voted last month to increase Rickenbacker Causeway tolls by 25 cents to $1.75 to fund a $31 million reconstruction and widening of Bear Cut Bridge.

Broad Causeway

The town of Bay Harbor Islands, which owns and operates the Broad Causeway, took out a $10 million loan for extensive work on the long eastern bridge, which has a drawbridge in the middle. Bay Harbor has been planning the project, which also includes some minor work on three other causeway bridges, for three years, said Town Manager Ron Wasson. The drawbridge span will be replaced along with the bridge tender’s house, and structural supports will be shored up and covered with a protective coating, among other work, Wasson said.

The 62-year-old bridge is also considered functionally obsolete because some elements don’t meet current standards, including lanes that are too narrow and lack a median barrier, and sidewalks that are unprotected from motorized traffic by barriers. Those cannot be fully brought up to modern standards without rebuilding the bridge, but the repair project will add at least 20 years to its lifespan.

“The good thing is, the bridge is a very well-designed bridge,” Wasson said. “Keeping it updated is something we spend a decent amount of money on.”

FDOT plans to entirely replace several South Florida bridges under its jurisdiction, including two in Broward as well as the Southwest First Street drawbridge over the Miami River. The substructure of the 1929 Miami bridge is rated as poor.

FDOT plans to replace the drawbridge in 2018 — an $82 million project that could last two years. The result will be a higher bridge to give more clearance for boats, said Dennis Fernandez, FDOT’s local structures maintenance administrator.