As a teenager, Shirley Robinson and her friends used to walk barefoot down the center of Clements Ferry Road in the 1970s.

“You could lay in the middle of the road and look at the stars,” she said. “It was clear and dark and quiet. Those times are long gone now.”

Robinson was one of about 150 people who turned out Tuesday to hear plans for Cainhoy Plantation, 9,000 acres straddling Clements Ferry Road that could one day be home to 20,000 people.

A mixed-use development of residences, businesses, parks and more could be built on the site over the next half a century, according to the city of Charleston planning department and representatives of the owners, the family of the late Harry Frank Guggenheim.

The development will have a density limit of 2.1 units per acre, including about 3,200 acres of wetlands and marsh, meaning the site could have 4,300 residences.

Many at Tuesday's meeting expressed concerns, not about the potential development, but about the current traffic situation on Clements Ferry, the only access to the area.

“I figure the growth is coming whether we like it or not,” said Sarah Johnson who lives near the proposed development. “My big concern is whether we will be able to get out of the area if there is an emergency. The road needs to be taken care of first.”

Berkeley County Councilman Tim Callanan called Clements Ferry “a frustration that a lot of you have to deal with on a daily basis.”

A $20 million project to widen 3.6 miles of Clements Ferry — from Interstate 526 to Jack Primus Road — to two lanes in each direction with a center turn lane and a multipurpose trail on one side has been in the works for years. The project is part of a seven-year, 1-cent sales tax program that was approved by Berkeley County voters in 2008.

Plans now call for putting shovel to dirt in spring 2015, Callanan said.

“Even though we are giving (the state Department of Transportation) the funds to do it, they apparently lack the resources to get this done in any sort of reasonable period of time,” Callanan said.

Matt Sloan, who represents the Cainhoy Plantation landowners and is also president of the Daniel Island Co., said the road widening goes hand-in-hand with the Berkeley County School District's plans to build a new high school on the Cainhoy tract near Nelliefield Plantation, set to open in 2017.

Development of the Cainhoy tract will start in that section, which is on the south side of Clements Ferry. A 1.7-mile road will be built to reach the high school site.

“This area is ripe for a retail center,” Sloan said. “I'm still amazed there's not a supermarket here, so those discussions are getting ready to happen, but the thing that will launch first is the high school.

“I believe Daniel Island demonstrates that if you build schools, people will want to live by them, so I expect to see that happen first.”

A goal is to create an area where people will live, work, shop and learn, said Scott Parker of DesignWorks, who is working for the landowners.

“Everything that we are talking about here are things that make for a great place to live, things that make for a great community,” he said. Plans call for considering the current habitat, past uses of the land and a diverse economic strategy, he said.

The parcel is in the city of Charleston and Berkeley County. Sloan said it is not part of a current movement by Daniel Island residents to annex into Charleston County.

Plans for the neighborhood are set to go before the Charleston planning commission on Nov. 20.

Reach Brenda Rindge at 937-5713 or @brindge on Twitter.