SB County supervisor wants Marines to expand into wilderness areas A San Bernardino County supervisor is proposing that the Marine Corps leave a popular off-roading mecca intact and instead expand its Twentynine Palms training center into two wilderness areas. The military is considering enlarging the 932-square-mile base to the west, taking in the Johnson Valley Off-Highway Vehicle Area, and to the east, right up to the edges of the Sheephole Valley and Cadiz Dunes wilderness areas. But the federally protected wilderness could become new live-ammunition training grounds in an alternative plan suggested by San Bernardino County Supervisor Brad Mitzelfelt. The supervisor has asked Sen. Dianne Feinstein's office to consider removal of the wilderness designation from more than 150,000 acres in the two areas to accommodate the Marine Corps Air Ground Combat Center expansion. He contends the land has little value as wilderness. And keeping Johnson Valley open for the estimated 800,000 recreational visits a year is essential to the economies of the High Desert towns of Yucca Valley, Joshua Tree and Twentynine Palms, Mitzelfelt said....