I just wanted to make some corrections for the destination report from May 2002. Slippery Rock Creek is my home creek and I'm the American Whitewater volunteer streamkeeper for the lower section.
The first correction needed is for the difficulty of the rapids. The upper section from Kennedy Mills bridge down to Eckert Bridge is class III at normal water levels, maybe class II at low summer water and class IV at HIGH water. The lower section from Eckert to Harris bridge is normally class II, but can get some MONSTER holes at high water.
The sad truth is that two rescuers were drowned here on that body recovery. Pay your respects at the plaque on Harris bridge.
The length of the trip from Eckert Bridge to Harris bridge (the easier class II lower section) is closer to 3.5 miles than 6 miles. There is a trail along the river right side of the creek for foot shuttle hiking, but it is a strenuous hike - plan on about two hours minimum.
If you plan on canoeing the creek, note that state park regulations require that you have flotation in your boat. There's a reason for this folks - don't be a statistic.
For more info on access, gradient and rapids check out the Slippery Rock Creek page on American Whitewater.
American Whitewater website: http://www.americanwhitewater.org/