I lived in Livermore for about two years to help build the Wente Vineyards golf course. Helping build the course is one of the highlights of my life. I worked damn hard to help grow-in and open the course– quite often there before sunrise and well after sunset. When I had a free minute I rode Del Valle and a few other places back then, around 98. Most of the trails I just rode (see links below) were not there back then…glad to see the additions.
routes: http://www.geoladders.com/show_route.php?route=61289 | http://www.geoladders.com/show_route.php?route=61288
some great xc stuff. pretty clean. flowy. mix of dirt road, and great 1 track.
^a Yeti I borrowed from my cousin