*phew* I just traced over 200 miles of the Hetch Hetchy Aqueduct/pipeline, using USGS DRG, Urban Area, and Yahoo satellite; all the way from the head in Tuolmne to the terminus at Crystal Springs Reservoir, including pipelines 3 and 4 around the south of the Bay.

I'm not sure if this was easier than finding all the right NHD data, pulling it together, and converting to .shp and then to .osm.