Oursan Trail is a 3.3 mile lightly trafficked out and back trail located near Orinda, CA that features a lake and is good for all skill levels. The trail offers a number of activity options and is accessible year-round. Horses are also able to use this trail.
A trail permit is required, and you must register at the trailhead. The permit is valid for a year and may be used at other EB Watershed reservoirs. Purchase permits online at: http://www.ebmud.com/recreation/east-bay-trails
Nice little trail I always did along with other trails. Very shady and can be done any time. It drops off Bear creek with a little drop in elevation and is almost entirely in the shade.. The 1st right is a trail that goes up to Briones res. A little farther up towards San Pablo on a day I was solo I got within 10' of a half dozen deer. Memorable day...
13.5? Make that 16.5miles with 1800' of elevation gain according to Strava. This is a serious hike. Took us 5hrs to complete.
Overall I would not recommend at this time. The trails on the north side are completely beat up by a combo of the rain and cow tracks. It's brutal on the feet and ankles, not to mention, not very much fun.
This would be a 4 star hike if it wasn't for the beat up trail.
A long hike -- 1/2 marathon! Don't forget to get your trail permit. Fun to walk around a lake. Saw hawks, Canada geese, turkeys, crows, swallows. Early spring day was sunny and warm. Most of the hike is pretty open, so it's probably pretty warm in the summer. There's a nice section in a beautiful, cool grove of grizzled oaks. Some benches in this section for quiet contemplation.