PORTSMOUTH, N.H. (AP) – Two tidal power companies that planned to place turbines in the Piscataqua River between Maine and New Hampshire have withdrawn their preliminary permits.

The Portsmouth Herald reported Thursday that UEK Corp. of Annapolis, Md., and Oceana Energy Co. of Washington, D.C., pulled their federal permits, which were good for another year. UEK said its plan to place a turbine “park” in the river north of Portsmouth isn’t economically feasible, given the river’s depth and residents’ concern over its fragile ecology.

The New Hampshire Tidal Energy Co., a subsidiary of Oceana Energy, proposed a turbine project under the General Sullivan Bridge.

The turbines would have used the power of the tides to produce energy, similar to wind turbines.