Sasol, a South African energy giant, plans to spend between $16 billion and $21 billion to build a plant in Calcasieu Parish that will convert natural gas to liquid fuel and house an ethane cracker complex.

That’s roughly double the size of the investment the company first announced in September 2011. The plant, which will be located in Westlake, is set to create more than 1,250 direct jobs with an average annual salary of nearly $88,000, plus benefits. The Sasol plant will create about 7,000 construction jobs, according to estimates from Louisiana Economic Development.

Sasol’s board recently approved going ahead with front-end engineering and design work for the plant. Operations at the facility are set to begin in 2017, and full employment should be reached two years later.

A study commissioned by LED and performed by the LSU Division of Economic Development estimates the Sasol project will have a total economic impact over the next 20 years of $46.2 billion and the project will be one of the top 10 drivers of the Louisiana economy once it is completed. Gov. Bobby Jindal’s office said the project is the largest single manufacturing investment in the state’s history and one of the largest in U.S. history.

“This project is a giant step forward to help our country become more energy independent and less reliant on foreign sources of energy,” Jindal said in a news release.