Thread might be old, but its still one of the first hits off of google. I looked back at some biking data and took averages over two rides on the 59th st QB bridge on a garmin + altimeter watch.

Manhattan turnaround to crest - 81' climb over 0.61mi (3221') - 2.5% grade
crest to Queens turnaround - 115' climb over 0.73mi(3854') - 3.0% grade