Some $461 million in anticipated federal money is allotted for Interstate 526 widening in a new funding plan that faces a key vote next month.

Even if the plan survives intact, it still would leave the project $100.5 million short of what’s needed to make the entire length of the 19-mile highway six lanes.

The state Department of Transportation plan includes nearly $180 million in federal funds expected to be available for construction of a new interchange for I-526 and Interstate 26.

In addition, $160 million in federal funds would be used to widen I-526 from Savannah Highway to Clements Ferry Road. Funding for widening the rest of the interstate has not been identified.

The DOT plan to use federal funds for I-526 improvements is included in a $1.4 billion blueprint for interstate upgrades approved this month by the agency commission. The interstate budget includes $867 million in anticipated federal money that will be used for four projects around the state, including I-526.

The DOT interstate upgrade plan hinges on an upcoming vote by the State Infrastructure Bank board on Sept. 9. At issue for board members is whether to OK state financing for $555 million for DOT-recommended interstate improvements in the Upstate and Midlands.

If the board approves that financing package, federal funds currently allotted to the higher-ranking projects in other parts of the state could be re-directed to the Lowcountry for I-526, which currently is No. 4 on the DOT priority list for interstate upgrades.

“The SIB will have the final call. If they change anything, it could tip the dominoes over,” said Pete Poore, DOT spokesman.

The General Assembly Joint Bond Review Committee also must approve state financing for the interstate improvements.

I-526 is the big-ticket item of the $1.4 billion plan, which is a blueprint for interstate improvement spending through 2023.

The SIB will be asked to consider spending $240 million of the $555 million to improve the interchange of Interstate 85 and Interstate 385. The state funds are available because the General Assembly this year approved $50 million annually for 10 years to be used for prioritized interstate projects ranked by DOT staff. Bonds will be issued to finance the work.

Meanwhile, an ongoing study of the I-526 corridor has made some preliminary recommendations for improving traffic flow. The study says that the most costly improvements such as widening could be delayed for up to 10 years if other less expensive measures were implemented.

They include increased carpooling, employers providing bus passes, staggered work times and shifting truck traffic away from I-526. The analysis has concluded that a designated express lane for carpoolers or people who pay a toll would not be appropriate for I-526.

Widening of I-526 will include improvements to interchanges other than the main traffic choke point at I-26. They include U.S. Highway 17, Paul Cantrell Boulevard, Leeds Avenue, Paramount Drive and International Boulevard.

That could change, however, as design efforts get underway and the DOT proceeds with the review process required under the National Environmental Policy Act, said Mark Lester, DOT director of planning.