Only four gaps remain in all of West Virginia to complete the 238 mile Parkersburg to Pittsburgh Corridor. The terminus of the Marion County rail trail in Fairmont represents one of those gaps.(Chris Schulz / WVPB )Standing at the end of the 2.5-mile Marion County rail trail on the outskirts of Fairmont, the city’s Planning and Development Director Shae Strait sees nothing but possibility in the Parkersburg to Pittsburg Corridor, better known as…