At the summit of Mount LewisMount Lewis is a California Coastal Range peak located in the northwest section of the Diablo Range. More precisely, it straddles the north-central edge of Santa Clara County and is the eighth highest peak in that county. It can also be described as being just 4 miles distant from the Ohlone Regional Wilderness’s southern boundary. Mount Lewis is a rarely visited peak due to its position on private property and the miles involved in getting there. As an out-and-back day hike from Del Valle Regional Park, the trek involves 22 miles and over 4000 feet of elevation gain. To some of course, it is this isolation and obscurity that makes Mount Lewis such an alluring and worthy destination.
Dead Oak well above Arroyo Valle. Alameda Creek ValleyGeographic landmarks surrounding Mount Lewis include both Oak and Poverty Ridges to the west; Valpe and Beartrap Ridges to the east; Hamilton Flat and Wahab Ridge to the north. On a clear day, Mount Lewis has a sweeping view that extends 260 degrees northeast to northwest. Mount Eylar is seen seven miles to the east; Black Mountain and Mount Day, 3 and 4 miles to the south/southwest; while both Mount Copernicus and Mount Hamilton command the distant southern skyline. Most striking, however, is the broad, picturesque valley beneath the slopes of Mount Lewis, expansive yet seemingly walled in by the high slopes of Valpe and Oak Ridges. Here the headwaters of Alameda Creek begin where during Winter and Spring vibrant feeder streams drain the surrounding slopes and add to the frothy confluence of Valpe and Alameda Creeks. Alameda Creek continues to gather momentum as it winds its way to lower elevations, passing through Sunol Regional Wilderness and Niles Canyon before finally reaching San Francisco Bay.
Jeep trail near Mount LewisDrive to Del Valle Regional Park in Livermore. When entering the park, secure an Ohlone Regional Wilderness hiking permit from the attendant at the kiosk. The permit, good for one year, is also a map of Ohlone Regional Wilderness. There is also a parking fee. Park near the Lichen Bark picnic area. Begin hiking at the Lichen Bark trailhead. At mile .91 stop at the Ohlone Trail sign-in panel. The next 6 miles ascend dramatically with over 3000 feet of elevation gain. When you reach mile 7.03 and an elevation of 3640 you will be at the Rose Flat road junction (trail marker #32 on the map). Here you will leave Ohlone Regional Wilderness boundaries. Go south on a dirt road that takes you to a four-way junction (BM 3756 on the USGS Mendenhall Springs Quadrangle). Go southeast. At the next junction marked “3645” on the Mendenhall Springs Quadrangle turn right, heading due south. This takes you to Hamilton Flat. Continue south on Hamilton Flat, passing a large reservoir through which Valpe Creek drains. You will have now entered onto terrain represented on the USGS Mount Day Quadrangle. Continue a due south course until locating a jeep trail that rises and bears east to Mount Lewis. Prior research on Google Earth and Google Maps will assist in navigating the myriad jeep trails and dirt roads that criss-cross the terrain between Rose Flat and Mount Lewis. A pre-determined GPS route will also insure an efficient and timely course towards Mount Lewis. USGS Quadrangle maps can be purchased on the internet.
Horse near Ohlone Wilderness Hamilton Flat ReservoirAt the time of this writing, Mount Lewis stands on privately owned lands. To hike here legally, you will need permission from the landowners.
CampingCamping is available nearby at Del Valle Reservoir in Livermore.
External LinksList of Summits in Santa Clara County
The Diablo Range on Wikipedia
Central California Coast Ranges
Photo Gallery from Mount Lewis hike
Bob Burd's Trip Report.