The clock is ticking on a deal to buy thousands of acres of land needed to revive Biscayne Bay and the Everglades, say environmentalists who packed a South Florida Water Management District board meeting Thursday. The deal, a fraction of a once-massive purchase brokered by former Gov. Charlie Crist to scoop up all of U.S. Sugar’s 180,000-acre empire, is set to expire Oct. 15. Environmentalist worry that unless the district acts quickly, time will run out. The deal covers 46,800 acres south of Lake Okeechobee that could be used to store and clean excess lake water before sending it south to the Everglades.