Billionaire Mitchell Rales’s plans for his Glenstone estate and art gallery got a boost Thursday when a Montgomery County Council committee voted 3-0 to allow a sewer hookup for Rales’s 200-acre property.

The proposal, which previously had been rejected by the county planning board, now goes to the full nine-member council, which could vote next week. Then it would go to the Maryland Department of the Environment for final approval.

Lawmakers on Thursday acknowledged that authorizing the sewer hookup would give Rales something that his neighbors generally cannot obtain because of county regulations. But they said it would be in the public interest to allow the estate to get rid of its septic system.

Rales, a co-founder of the highly successful Danaher Corp. and No. 117 on the Forbes 400 list of wealthiest Americans, has said he wants the sewer line for a proposed gallery on his property that would rival the East Building of the National Gallery of Art both in size and in its expansive collection of abstract expressionists.

He and his wife, Emily Wei Rales, open their gallery to the public on Thursdays and Fridays by appointment only. The collection, according to Rusty Powell, director of the National Gallery, is “one of the world’s most important” in the post-World War II era. It includes works by Calder, Matisse and Rothko, among others.

From left to right: Emily Wei Rales, Matt Rales, Mitchell Rales and Strathmore CEO Eliot Pfanstiehl. (Photo by Margot I. Schulman/Strathmore/PHOTO BY MARGOT I. SCHULMAN/STRATHMORE)

Glenstone, on Glen Road in Potomac, is in a sector of the county where sewer is generally banned, and septic is required to help tamp down growth. At Thursday’s hearing, council members said they thought a sewer hookup might be more environmentally friendly than septic.

“It has been argued that going through the sewage treatment system is better [for] water quality . . . than using large septic,” said Council President Roger Berliner (D-Potomac-Bethesda), who chaired the panel reviewing the request. “If you consider the energy input into running the septic system, clearly sewer would be better.”

But local environmental groups and some neighbors are opposed, noting that, at 3,000 feet, the Glenstone sewer line would be one of the longest ever approved by the county and would run across an environmentally vulnerable stream.

“In this case you are digging under a stream,” said Mary Dolan, an environmental expert at the county planning agency. “I agree that they are spending quite a bit of money to avoid the environmental impact with the installation of the line. But there is still the danger of breaking the line and having it go directly into the stream or for the line to be eroded, as many of the lines in the county have been. Then you have a direct discharge of untreated sewage.”

Rales did not attend Thursday’s session, but a spokesman said he was cautiously optimistic.

“This is a very big step in the process but we need to see what the full council decides. If it does vote favorably it will be an incredible opportunity for the residents of Montgomery County,” said Charles Maier, a public relations executive whom Rales has hired to help shepherd the project.

Rales has mounted a quiet but deliberate campaign in Montgomery to win over the public and politicians, saying he wants to share more of the collection. In his first media interview in 27 years, Rales told The Post that a sewer connection would enable Glenstone to use more of the outdoor space to display large sculptures. While Rales acknowledged that he could make do with a septic system, he said he is trying to create a “hundred-year plan” for his estate and worries that the need to replace septic every 25 to 50 years could threaten the exhibits.

Ginny Barnes, a community activist in Potomac and an artist, said she appreciated Rales’s art collection, but said he was being given preferential treatment.

“I felt that he was going to get whatever he wanted because he is a billionaire,” she said.

“They had stars in their eyes,” Barnes said of the council panel. Besides Berliner, it includes Council members Nancy Floreen (D-At large) and Hans Riemer (D-At large).

The panel also approved a sewer connection for Shri Mangal Mandir, a religious institution on New Hampshire Avenue in Silver Spring. At the same session, the council panel rejected sewer requests from two homeowners who live a few miles from the Glenstone estate, saying they did not meet the qualifications for a waiver of the rules.

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