I've heard these trails are fast and have little elevation change. I've been there twice but each time the trails were closed due to trail conditions (wet). These better be some pristine trails to be closed so often and seemingly without much cause. Call the parks department first to make sure the trails are open because these trails are far away, no matter where you live.
"From Raleigh, take US 1 South towards Sanford. Take the New Hill exit and turn left on New Hill Rd. Go about 3 miles. Entrance to Harris Lake Park is on the right. Go through the park and take a left at the stop sign. You will see the sign for Hog Run straight ahead. Park in the lot to the right.
http://www.singletracks.com/item.php?c=1&i=640