Wednesday, January 4, 2023

Las Trampas Rocky Ridge

Rocky Ridge and the Diablo Range
5 miles loop, 1100 feet elevation gain
Difficulty: Easy-moderate
Access: Paved road to trailhead, no entrance fee required

Sweeping views of the Oakland Hills, San Francisco Bay, and Mount Diablo make Rocky Ridge the premier hike of Las Trampas Regional Wilderness in California’s San Francisco Bay Area. In fact, short of the most well-known peaks in the Bay Area- such as Mount Diablo, Mission Peak, and Mount Tam- I found that Rocky Ridge had some of the best views in the Bay, its panoramas incorporating the grassy hills of East Bay, the calm waters of the Bay itself, and just about every major peak in the region. This hike is especially nice in winter and spring, when the surrounding ridges and hills are a vibrant green; an additional plus is that this hike, although still popular, sees fewer hikers than Mission Peak or Mount Diablo.

I hiked Rocky Ridge on a sunny but hazy winter day. The trailhead at Bollinger Canyon Staging Area can be reached from either I-580 in Hayward or I-680 in San Ramon; coming from the Bay, I hopped off I-580 at exit 37 for Grove Way and Crow Canyon Road. I followed Crow Canyon Road north for eight miles through Crow Canyon and over the mountains, turning left onto Bollinger Canyon Road at the first stop light after the steep descent towards San Ramon started. I then followed Bollinger Canyon Road north to the end of the road in Las Trampas Regional Wilderness: there was a main parking lot with room for about 40 cars, with parking alongside the road leading to the lot and a secondary lot with room for another 50 cars about a quarter mile back down the road. Las Trampas Regional Wilderness is a fairly popular hiking destination, so expect the main lot to fill on weekends. There was a pit toilet at the trailhead.

Three trails left from the Bollinger Canyon Staging Area: the Bollinger Creek Loop Trail and the Rocky Ridge Trail started from a gate on the north side of the lot, while the Elderberry Trail left from the south side of the lot. I started out the hike on the Rocky Ridge View Trail and would return later in the day on the Elderberry Trail.

The Rocky Ridge View Trail was a paved road (no vehicles allowed) that led steeply uphill from the staging area directly towards the crest of Rocky Ridge; it was ironic to be walking up a paved road in a “regional wilderness.” Climbing 700 feet in three-quarters of a mile, the trail, which was almost completely out in open, grassy slopes, was a good workout. 

Paved Rocky Ridge View Trail leading towards the ridge
Views initially encompassed just Las Trampas Ridge, Bollinger Canyon, and nearby cows grazing the grassy hillsides, but about halfway through this initial ascent Mount Diablo began poking out behind Las Trampas Ridge. Soon, views to the north began improving, too, and by the time the Rocky Ridge View Trail reached a gate about 200 vertical feet below the communications towers on the crest of Rocky Ridge, I could see as far as Mount St. Helena to the north.

Las Trampas Ridge and Mount Diablo
At 0.75 miles, the paved Rocky Ridge View Trail reached a gate that prohibited further entry. The land beyond the gate is administered by the East Bay Municipal Utility District (EBMUD) and is only accessible by permit; the Rocky Ridge View Trail split from the paved road here and over the next quarter mile, it was a pleasant dirt trail leading gently up along the hillside until it reached the crest of Rocky Ridge, just over one mile into the hike. The trail skipped visiting the transmission towers at the top of Rocky Ridge, as those are on EBMUD land; however, there would still be plenty of good views from along the ridge.

Mount St. Helena and Las Trampas Peak
Over the next 1.6 miles, the Rocky Ridge View Trail followed the undulating crest of Rocky Ridge, offering astonishing views over much of the San Francisco Bay Area. Looking west, I was able to see most of San Francisco Bay at many points along the trail, with the Santa Cruz Mountains rising across the Bay. Loma Prieta, Black Mountain, Montara Mountain, and the Sutro Tower were particularly notable landmarks across the Bay; unfortunately, a layer of haze closer to the Bay prevented me from seeing much detail in the San Francisco skyline. Mount Tam was often visible north of the city, the body of the ridge itself blocked many of the views to the north between Mount Tam and Mount St. Helena. Mount Diablo and Las Trampas Ridge made up the heart of the view to the east, while the hazy Tri-Valley to the south was bound by more peaks of the Diablo Range on its far end.

Hazy Diablo Range views
Mount Diablo rises over Bollinger Canyon
Despite its name, the crest of Rocky Ridge is largely grassy, with just minor rocky outcroppings. However, those existing outcrops were worthy of a closer look: the underlying geological formation of Rocky Ridge consists of Cenozoic marine sandstones of the Briones Formation. These sandstones are chock full of fossilized shellfish: take a closer look at any of the rocks along the ridge and you’re sure to spot these densely packed fossils.

Fossilized shells in the Briones sandstone
The trail wandered along the ridge and passed intersections with the Rocky Ridge Loop Trail and the Sycamore Trail around 1.6 miles and then passed a junction with the Cuesta Trail at 2 miles; at each fork in the trail, I stayed on the Rocky Ridge View Trail, which kept me along the top of the ridge, hiking past cows munching on the ridge’s plentiful grasses. 

Cattle grazing on Rocky Ridge
At 2.4 miles from the trailhead, I passed a junction with the Devil’s Hole Trail and then came to a glorious viewpoint on the ridge at the start of an extended descent along the trail. From this position on the ridge, I had a wonderful south-facing view. Rocky Ridge’s grassy crest faded away as it led to the south from here, with the many peaks of the Diablo Range rising beyond. Mission Peak and Mount Hamilton were among the well-known peaks visible from here; I also marveled over the many layers of rolling green hills below me that stretched down towards the Castro Valley area, separating Rocky Ridge from the suburbs of East Bay.
View south along the Diablo Range from Rocky Ridge
Oakland Hills and Santa Cruz Mountains
Leaving this lovely viewpoint, the Rocky Ridge Trail descended more steeply, dropping 200 feet over the next third of a mile until the trail made a sharp turn to the left, leaving the ridge and turning into the Elderberry Trail at 2.8 miles. A bench at this sharp turn provided a nice spot to stop and enjoy the ridgetop views a final time.

Looking back at Rocky Ridge
The Elderberry Trail descended steeply as it left Rocky Ridge, dropping quickly into oak woodlands as it headed north. Over the 1.7 miles of trail back to bottom of Bollinger Canyon, the Elderberry Trail generally stayed in the woods, although it broke out into some grassy stretches at times for limited views of Rocky Ridge above, Las Trampas Ridge across Bollinger Canyon, and the top of Mount Diablo on some occasions. At 3.4 miles into the hike, the descent along the Elderberry Trail leveled out a bit and the trail undulated over a series of small gulches; at 4.2 miles, the trail began to descend steeply again, with the downhill ending when the Elderberry Trail arrived at the bottom of Bollinger Canyon at 4.6 miles. Parts of the trail were quite muddy, even two weeks after the most recent rains; frequent use by grazing cows had turned stretches of the trail into muddy nightmares.

Bollinger Canyon and the Tri-Valley
At the corral at the bottom of Bollinger Canyon, the Elderberry Trail intersected another dirt road; the right fork led towards the corral camp staging area while the left fork traveled up the canyon towards the staging area where I had parked. I followed the left fork for a final 0.4 miles along the floor of the canyon, traveling through alternating grasslands and oak woodlands with the gentlest of uphill inclines until I closed the loop at the parking lot.

While the paved portion of the Rocky Ridge View Trail has little to recommend about it, the view-packed traverse along the top of Rocky Ridge makes this hike one of the better outings in the San Francisco Bay Area. Hiker traffic was moderate; I saw over 50 hikers in about three hours, although everyone was spread out and I was able to have many of the nice viewpoints along the ridge to myself. Pick a clear day when the hills are green to enjoy the views on Rocky Ridge in Las Trampas Regional Wilderness.

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