BUTLER TWP — A proposed expansion of the Ellen O’Brien Gaiser Center cleared a procedural hurdle Tuesday, but township planning officials expressed reservations about the project’s plan to build a new office and residence hall on top of an underground stormwater management system.

The conditional approval for the project’s land development plan by the township’s planning commission is another step toward final approval for the expansion. The project would add a 7,800-square-foot, two-story building to the facility’s east side for administrative offices and overnight residents for female clients of the drug and alcohol addiction treatment center.

But township zoning officer Jessie Hines and township engineer Dan Deiseroth expressed concerns about the building’s placement over a 72-inch corrugated metal pipe that is about six feet underground that holds stormwater. The proposed building would be on top of part of that pipe.

It’s a design that isn’t prohibited by township code, Hines and Deiseroth said, so the commission could not deny the plan on those grounds. But both men urged the project planners to reconsider the proposal, and said that the life of the pipe — 30 or 40 years — is not anywhere near that of the building, which is more than 100 years.

“You’re basically building future problems into the plan” with this layout, Deiseroth said.

Gaiser Center representatives said they are open to considering other options, but that the proposed layout wasn’t prohibited by Pennsylvania’s construction code. Hines said the matter would have to be discussed further during a review before the project receives final approval from the township.

The expansion is part of a plan that Gaiser Center officials have said was prompted by an increase in illegal drug use in Butler County as well as a rise in the number of women requesting addiction treatment services at the facility.

The expansion would increase the number of clients the center serves from 29 to a maximum of 45.