Montgomery County Executive Isiah Leggett wants to create a $3 billion life sciences research center at a former sludge composting facility site north of White Oak, and on Friday he announced the private partner the county selected to build it.

Percontee, a family real estate firm based in White Oak, won a county competition to develop a 115-acre, county-owned former Washington Suburban Sanitary Commission plant east of Route 29 off Industrial Parkway.

Percontee long operated a sand and gravel quarry on 185 acres it owns next door off Cherry Hill Road. The company plans to integrate the two properties and build a 300-acre mix of university research facilities, offices, housing, hotels and retail to leverage and serve the consolidated headquarters of the Food and Drug Administration next door.

The county property, often referred to as Site 2, processed sludge into compost from 1983 until it closed in 1999. The county purchased the property for $10 million in 2009 with an eye on redeveloping it.

Leggett (D) said in a news conference on Friday that the life sciences center, to be called LifeSci Village, would become a “true mixed-use legacy development project” that would drive the economy for eastern Montgomery County for generations to come.

“This will literally turn a brownfield into a world-class bio sciences employment and research center,” Leggett said.

Montgomery County Council member Nancy Navarro (D-Eastern County) said that residents in the county’s eastern area were eager for a core center of employment and commerce.

“This is the part of the county that has been waiting for a very long time,” she said.

Jonathan M. Genn, Percontee executive vice president and general counsel, said the company would develop the site through an affiliate, Global LifeSci Development, and create a hub of science and research that — with its location next door to the FDA — would serve as the “exclusive port of entry into the U.S. public health market.”

The area is also adjacent to where Adventist HealthCare plans to relocate Washington Adventist Hospital. The new hospital, which would have 249 inpatient beds, awaits state approval but could open as early as 2015.

Although there are life science hubs elsewhere in the country, Genn said, “there is only one FDA in the world, and it is right here in White Oak.”

Most of the development needs county approval and is waiting for a master plan for the area that likely will take one to two years, Genn said. Construction of some buildings could begin before then, and Genn said “very prominent” area universities have expressed interest in locating operations there.

Percontee is owned by the Gudelsky family, which has been developing land in the county since the 1950s. Members of the family and the companies it own have contributed thousands of dollars to local political campaigns in recent years.

Percontee won the deal by beating out two established development firms, Hines and Trammell Crow, according to Steve Silverman, director of the Montgomery County Department of Economic Development.

“We were impressed with their vision, their expertise and the land consolidation,” Silverman said of Percontee’s selection.

Genn said the company had met with citizens at dozens of community meetings and that Percontee’s interests aligned closely with those of residents.

“When we identified the attributes that we want to be here, everyone said they wanted to see the same things,” he said.

He said he thought Percontee won the deal because of its interaction with the community, the extra land it could contribute and its plan for the area, one that, in addition to medical and research uses, includes parks, walking trails and a central boulevard for shopping and recreation.

“I would like to think that it was because of the grand vision we had for a bold transformation,” he said.