One of the largest employers in Philadelphia and Neshoba County is moving ahead with a $57 million expansion.The Meridian Star reported that the expansion and modernization of Weyerhaeuser's Philadelphia lumber mill is expected to take 10 months.Monte Simpson, manager of Weyerhaeuser's Public Affairs, said the mill has about 180 workers.Simpson said construction is well underway. He said improvements include a new sorting and stacking system that will be in place next year and a new drying kiln that will go online this summer.