HARLINGEN — The long-awaited closure of the Rio Hondo mechanical lift bridge for a major overhaul will begin Monday.

A sign adjacent to the bridge confirms the date TxDOT plans to shut down the east-west link over the Arroyo Colorado on FM 106.

How long that bridge’s closure will cut Rio Hondo in half remains to be seen.

Local officials have said they hope it will only last six months, but TxDOT’s engineer on the project, Sergio Sustaita, has said it could be up to 11 months.

Rio Hondo officials originally had sought work to begin earlier this summer, but delayed it because FM 106 is a hurricane evacuation route from South Padre Island and Port Isabel.

The $12 million retrofit of the unique yellow bridge, which opened in 1953, poses challenges to engineers and contractors because it is the only such mechanical lift bridge in Texas.

Rio Hondo officials say there are only two others like it in the country, in California and in Louisiana. The Louisiana bridge no longer raises and lowers, merely serving as a fixed crossing.

Some of the parts for the bridge retrofit will have to be machined and manufactured from blueprints, officials have said.

The “official” traffic detour routes vehicles south from Rio Hondo on Williams Road to the I-69E/77/83 expressway in San Benito, which is 8.6 miles to the south. Then traffic will travel to FM 509 and head north until hitting FM 106 on the western side of the Arroyo Colorado.

A quicker east-west route across the Arroyo Colorado is available on Cemetery Road just 3.6 miles south of Rio Hondo. It’s not the “official” route because TxDOT rules say a detour like this has to route traffic over a state highway.

It’s about a five-mile transit to get from one side of Rio Hondo to the other, officials say.