LAKE CHARLES — Louisiana highway officials have agreed to their role in building a new Interstate 10 bridge over the Calcasieu River at Lake Charles.

The new Calcasieu Parish span is expected to cost about $2.1 billion. The Louisiana Department of Transportation and Development said Wednesday it had officially entered a pact with Calcasieu Bridge Partners. A legislative panel approved the deal Tuesday.

Construction could start this year and will take about seven years to complete. The project area runs from downtown Lake Charles westward to the I-10/I-210 interchange near Westlake.

The existing span is 70 years old and predates the interstate highway system. It is steep, has no shoulders and is often a bottleneck for travelers between Louisiana and Houston. The new bridge won't be as steep. Ships serving the port at Lake Charles would not need to pass beneath the new span.

State and federal governments will put up about $1.2 billion of the cost. Calcasieu Bridge Partners will cover the rest, and recover its money through tolls over a 50-year period. Profits could shorten the time the tolls are necessary, or could support other projects in five southwestern Louisiana parishes. 

Baton Rouge-area officials are still hoping to build a third crossing in its region to alleviate daily traffic jams on the I-10 crossing there.