The plant is spread on about 1,000 acres along the Mississippi River in Norco.
The expansion project will include construction of a large methanol unit, designed to compress natural gas into liquid to manufacture chemicals and plastics, reported The Associated Press.
Valero Refinery community relations director Taryn Rogers said Valero selected St. Charles Parish for the expansion because of its closeness to the Mississippi River and its docks as well as "the pro-business environment in Louisiana."
In 2012, Valero paid about $12m in property taxes in St. Charles Parish, while the expansion is expected to add another $3m to $5into the tax base.
The total tax roll in St. Charles Parish is nearly $131m and $115.3m comes from industry, including Valero, Monsanto, Motiva and Entergy.
