The plan for 12 townhouses on the undeveloped east side of Saco Island was approved by the the Saco River Corridor Commission Wednesday night, clearing one of the final hurdles before the project can be built. Saco Island Ventures LLC plans to construct the 12 buildings, each with two apartments, on six acres of the island, the latest of several projects to be proposed for the long-vacant site. The Saco River Corridor Commission voted 10-3 to approve the project's application. The commission, which has members from the 10 towns and cities along the river, signs off on projects that are within 1,000 feet of the Saco and smaller rivers in its watershed.