I often ride from Irvine civic center to South Orange County. A frequent route is the SD Creek trail to Irvine Spectrum, then Irvine Center Dr over the 405. I was told that there is an alternate route under the 405 that requires a little bushwhacking, but is passable. I checked the satellite image of the area, and see where it should be. I suspect the image is out of date, since the route described is kind of iffy.
The alternate should start where the route here http://ridewithgps.com/routes/2256598 ends, according to the guys description. Has anyone done this?