The Nature Conservancy is finalizing plans for its new $4.4-million headquarters at 620 E. Ohio St. downtown. The not-for-profit group is planning a two-story, 20,000-square-foot building that will take up about half a block between Easley Winery and the new six-story Maxwell condo and retail project. The Conservancy already tore down a building previously occupied by Nemec Heating & Supply Co., which sold it the property early last year (earlier post is here). The architect, locally based Axis, is working to design an energy-efficient headquarters with a â€œgreenâ€ roof, extensive landscaping and possibly wind turbines. The Conservancy plans to finalize a timeline for the project after receiving construction bids Feb. 13.