Well, that one was not close to Phoenixville, the 15% I ran across was on County Park Rd. near rte 23 by Warick County Park. However, if you want some local roads with grades in the double digits, you can try Union Hill rd, Rees/Howell Rd. for example. Whitehorse gets close in parts. Rte 29 in Mont Clare seems a little hilly to me.

I haven't ridden all of the choice hills around here, but I know there are several that are in the double digit range at least for portions of the uphills.