Columbia is reinventing downtown, that playground of the young, as a home for older folks, too.

Developers are planning an "active adult" apartment complex that would bring 156 units on 5 acres overlooking The Mall in Columbia off Governor Warfield Parkway. They would be the first Town Center rentals limited to people ages 55 and older.

Those units would add older residents to a downtown that has a significant senior population in luxury apartments and a retirement high-rise. Community leaders hope that is just the start.

"Why not Town Center?" said Donna L. Rice, downtown's representative on the Columbia Council. "Couldn't be a better place."

The senior apartments, on which construction is expected to begin in late summer or early fall, are part of a budding Town Center residential boom.

The Rouse Co. says work will start next year on 48 condominium units on Wincopin Circle - open to any age - and on a model home for the mixed-use high-rise planned next door.

John D. Rhoad Jr., whose McLean, Va.-based RMJ Development Group is handling the seniors project, is betting that more people in their final years of work or first years of retirement want to live within walking distance of restaurants, stores, trails and a library.

"It's providing our growing senior population a variety of options for housing," he said. "It's just not way out in the suburbs."

The four-story complex, called the Evergreens at Columbia Town Center, is planned to sit northeast of the Gramercy at Town Center apartments and the under-construction Governor's Grant townhouses.

Though development irks many Howard County residents, Town Center boosters are excited by the growth. They hope population increases will bring continued vibrancy to a downtown that in the past would slow after office workers went home for the night.

Rice said seniors apartments strike her as a particularly good idea.

"There are a lot of old-timers here in Columbia," said Rice, a resident for nearly 32 years who counts herself in that group. "If we don't pay attention to that, then the seniors will look for someplace else to go."

The draw of downtown among the middle-aged and older is evident. One of five people renting Gramercy apartments is older than age 50, said assistant property manager Ben Beerman. Sixty percent are at least 36 years old.

Beerman attributes the draw to the central location - and Town Center market forces. Gramercy's monthly rents range from $1,115 for a one-bedroom unit to at least $1,845 for three bedrooms.

"The closer you are to the mall, the more expensive everything is," Beerman said. "A lot of younger folks aren't making the money to live in the property."

Retirees are being priced out, too, and not just in Town Center. Some apartments in the county are reserved for low-income seniors, and many homes are being built for the affluent. But a real need exists for middle-income people, said Phyllis Madachy, administrator of the Howard County Office on Aging.

"Frederick County is attracting a lot of older people ... who don't need assisted living but want to live in smaller homes, and they want to live in homes that don't tie up all their assets," she said.

The Evergreens' developer said rising land costs are having a direct effect on rental rates.

"There's only so low they can go," said Rhoad, who expects that monthly rents at the Evergreens will be on par with the existing Town Center prices. "By having a diversity of floor plans and unit sizes, we really do try to provide a range so there is an affordable aspect to the pricing structure."

Madachy said any senior housing is good news. "It's needed so badly," she said.

Vantage House Lifecare Retirement Community is the only seniors complex in Columbia's downtown now, and the 13-story building is 97 percent filled, said marketing director Katie Travers.

Vantage House offers traditional retirement services - one meal a day, social activities, transportation and weekly housekeeping for people living in the 220 units - and both assisted living and nursing care for residents whose health deteriorates. The Evergreens will offer none of that. Instead, it will have an outdoor pool, spa, greenhouse, clubroom, fitness center, computer room, library and game room, Rhoad said.

He is scheduled to give a presentation about the project early next month to Town Center and Wilde Lake leaders; the property is near the boundary, between homes and the mall.

"It seems like a great transition to the downtown," said Alton J. Scavo, executive vice president of development for the Rouse Co.