WOODLAWN, S.C. --- Just a few short years ago, Sumter National Forest offered little more than timber and public hunting.

This weekend, mountain bikers from across the region will gather in McCormick County to open the third phase of an expanding trail network that has gained national acclaim.

"The International Mountain Bike Association has identified this area as an 'epic' trail system, which means it is with the best in the country," said Paul Farrow, the president of the CSRA chapter of the Southern Off-Road Bicycle Association.

For several years, the association has worked with the U.S. Forest Service, the South Carolina Department of Parks, Recreation & Tourism and other groups to secure grants to carve challenging mountain bike trails from federal lands along the Savannah River near Augusta.

On Saturday, the group will dedicate the newest section of the Forks Area Trail System, or "FATS," as the cyclists call it.

The new phase will include two runs totaling nine miles, Mr. Farrow said.

"With the other trails, now we have a total of 34 miles, and the new runs are connected to the older ones by less than one mile of public roads."

Mountain biking, one of the region's fastest-growing outdoor activities, is luring more and more out-of-town visitors to the national forest, and many of them stay in Augusta or North Augusta, he said.

"If you come out here on a weekend and look at cars parked at the trailhead, you'll see people from Columbia, Asheville, Atlanta -- even Florida," he said.

The first bike trails at Woodlawn opened in 2005 and have been gradually expanded since then.

The two new runs opening on Saturday will increase the total number of rides to six, each with its own riding experience -- and a unique name, including The Great Wall, The Skinny, Brown Wave and Deep Step.

In the new section, Big Rock takes riders over huge individual stone outcrops, and The Tower passes a historic but abandoned fire tower.

The trails were financed with grants from the Forest Service and the tourism department and supplemented by matching donations from the off-road bicycle association, which also contributed hundreds of hours of volunteer labor, Mr. Farrow said. The trail projects were managed by Long Cane Trails LLC, a company owned by mountain biker Bill Victor.

The trails are open year-round, with the exception of the first two weeks of the South Carolina's firearms season for deer, which begins Oct. 11.

Maps of the trails and details about volunteer opportunities and off-road cycling are available on the bicycle association's Web site, www.sorbacsra.org.