Stonington — After several nights of lengthy hearings and deliberations, Planning and Zoning Commission members unanimously rejected a plan Tuesday night to build a dental clinic on land zoned for manufacturing in front of the Ocean Community YMCA at Masons Island Road and Harry Austin Drive.

The commission ruled that Summit Street Development LLC of New London must first obtain a variance from the Zoning Board of Appeals before it can return to the commission for approval.

The commission ruled a variance is needed to develop the undersized lot, which is nonconforming under the town’s zoning regulations.

Although the regulations require a minimum lot of 80,000 square feet, the lot for the building is about half of that. Project attorney Theodore Harris argued during the hearings that because the lot existed prior to zoning, it can be used as long as the project meets requirements such as setbacks and buffers, which it does.

The commission worked to interpret the regulations and reviewed similar case law before making its decision Tuesday night.

Opponents and neighbors of the project told the commission they were worried about the impact the project would have on traffic, the character of their residential neighborhood and that the 9,290-square-foot building appeared to be three floors, not two.

Project architect John Walsh told the commission during the public hearings last year that the building is two stories. The second floor would not be finished and would be left open for storage, he said.

Plans called for 11 exam rooms and 28 parking spots. Three part-time dentists and two hygienists would work in the building, which would be open 9 a.m. to 5 p.m. weekdays and 9 a.m. to noon on Saturdays. The traffic engineer for the project had said it would generate 90 vehicles entering and exiting the property daily.

j.wojtas@theday.com