Excellent trails.
From I-80 in San Francisco, take I-80 east toward Oakland. Exit #27 toward Port Costa/Crockett. Turn left on Pomona Street. Turn right onto Crockett Blvd. and right again into staging area. From I-80 in Sacramento, take I-80 west toward San Francisco. Take the Pomona Street exit at Crockett. Turn right onto Crockett Blvd. and right again into staging area. From Hwy. 4 west, take the Vallejo/Crockett exit onto Cummings Skyway. Turn right on Crockett Blvd and left into the staging area.
http://www.singletracks.com/item.php?c=1&i=7208