Here's a link to
http://www.bikely.com/maps/bike-path...t-Constitution which is someone's tracing of the route. Up in the Bikely toolbar, you can pick "show" to see an elevation profile.
Looks like the 15% sections are a small proportion of the total. Since you'll be coming back down the way you went up, you may recognize the "steep descent ahead" clues, and be able to stop ahead of the descent to let the rims cool.