Given the forecast I figure we will need to stay away from the canal and any trails. So let’s try this new combination of old roads.

From the parking lot, turn left on 96, then take a right on Park Rd. Turn left on Railroad Mills. Take Railroad Mills until it tees with Probst. Turn right on Probst. Then turn right on Mile Square. Turn left on Van Voorhis. Turn right on Pittsford Mendon Rd, then right on Thornell. Take a left on to Mill Rd., then turn right on East. Take East back to Park Rd, turn left and follow Park back to 96. Turn left on 96 and return to the parking lot. Distance is 12.5 miles.

http://www.gmap-pedometer.com/?r=7702058

If you skip the left on Mill Rd to East loop, that will cut off about 2 miles.

Coming back on Thornell to 96 will knock off about ¾ mile.