(33', 20-15-g) NW of Potomac, District 6 Township, Montgomery County, MD. MD190 (River Rd.) NW 6.8 miles from jct with MD189 (Falls Rd.) in Potomac, E. on Pettit Way 0.3 miles to the bridge on the N. side of the road. (N39 04.360 W77 18.282) Photos by Jim Smedley 1-18-18.