HILLSBORO, Ore. -- The Port of Portland is beginning an environmental study of a proposed new runway at Hillsboro Airport.

The 2005 master plan for the suburban airport calls for the construction of an additional runway dedicated exclusively to small general aviation aircraft.

Officials say take-offs and landings are near capacity with continued growth expected.

The proposed runway will allow small single- and multi-engine aircraft to take off and land while corporate jet aircraft use the existing runway, which is longer and wider.

The environmental study is expected to take 18 months.