The renovation of Enterprise Mill more than a decade ago kick-started the adaptive reuse movement in the city's historic urban core. The 236,000-square-foot textile mill that had sat vacant for more than 20 years was transformed into high-class offices and apartments.

Impressive as Enterprise is, though, the $20 million property won't go down in the city's history books as the mother of all adaptive reuse projects. That title will likely be reserved for another mill situated 4,400 feet to the northwest: Sibley Mill.

With twice the acreage and square footage of Enterprise, the recently shuttered Sibley plant will test the abilities of the city's best-known redeveloper, businessman Clay Boardman, the driving force behind the Enterprise project.

"It's a beast," Mr. Boardman said. "It's such a huge project."

So huge that Mr. Boardman's development company, Augusta Capital LLC, and its partners at Savannah, Ga.-based Melaver Inc., which bought Enterprise Mill from him in 2006, have aligned with an international company that specializes in major redevelopment projects. Mr. Boardman and his associates declined to name the company.

No work will begin until Mr. Boardman, who has been under contract to buy Sibley from Avondale Mills Inc. for more than a year, closes on the sale. Environmental testing at the site has delayed the sale, but Mr. Boardman said he is certain the deal will close before the year's end. Sibley, like Enterprise, was built in the late 1800s.

His plans are to turn the 516,000-square-foot Sibley into a larger version of Enterprise, a mixed-use facility with office, retail and residential space.

"Sibley Mill is quite a challenge, if for no other reason than because of its enormous size," said Erick Montgomery, the executive director of Historic Augusta Inc. "Its location presents a challenge as well, since it is not in the heart of an area that has seen a lot of investment in recent years.

"But it will serve as a catalyst if it is successful, and I predict Harrisburg will benefit from the association."

Though Enterprise's living spaces are strictly rental, Mr. Boardman envisions Sibley as a development where residents could eventually convert the units into condominiums.

With the $30 million Kroc Center proposed directly across the Augusta Canal, Mr. Boardman sees Sibley as the first step toward revitalizing the surrounding neighborhoods.

"The ball is rolling now," he said. "There is real opportunity."

After the closing of the sale, work would begin at Sibley immediately, Mr. Boardman said. It would start with the demolition of nonhistoric add-ons, such as the weave room built in 1981 on the property's southeast side and several support structures on the north end that block the property's view from River Watch Parkway

It took 15 months from the start of renovations before Enterprise had its first residential tenant and 24 months before the entire project was completed. Mr. Boardman says he can follow the same timeline on the Sibley project, whose final price tag could run as high as $50 million.

By then, his two other adaptive reuse projects -- Sutherland Mill and the William Robinson School -- should be completed this fall.

With Sutherland Mill, a $7 million project, Mr. Boardman is creating medical offices in the 50,000-square-foot structure built in 1887 and used as a warehouse by Avondale Mills until it began shuttering its operations in the wake of the 2005 Graniteville train derailment. Mr. Boardman acquired the property from Avondale last year.

Unlike most medical office space, the "medical condos" at the Sutherland building will allow tenants to own their spaces and customize them as they see fit. The building is bordered by Walton Rehabilitation Hospital, Enterprise Mill and the Salvation Army. The St. Sebastian Road project, which will extend the street across the canal and in front of Sutherland, will link the area to the medical district.

"We've already talked to three or four large physicians practices," Mr. Boardman said. "There's no longer any land for them to buy around the hospitals."

No leases have been signed at the property yet.

The William Robinson School in the historic Summerville district will be converted into 27 luxury townhomes through a partnership with Mr. Boardman's brother, Braye, the president of Beacon Blue LLC.

Part of the $7 million project involves leaving much of the 1920s-era elementary school's interior intact, so it is possible that some units will have chalkboards on their walls or have a stage as part of the floor. The townhomes would share a common green that would be irrigated with collected rainwater.

Both the Sutherland and Robinson projects are being done in accordance with guidelines set by the U.S. Green Building Council in its Leadership in Energy and Environmental Design program, which requires a greater reliance on energy efficiency and use of environmentally sensitive products.