Irvine Ranch Natural Landmarks

Please note: Preregistration is required due to limited parking capacity. Carpooling is highly encouraged.

Start your weekend off by exploring the Agua Chinon wash and the Sinks through this self-guided opportunity. Designated trails will be open for self-guided trail use in OC Parks’ Irvine Ranch Open Space. Trail routes vary in distance and level of difficulty with choices ranging from easy one-hour walks to a strenuous 9.5-mile trek. Whether traveling by feet or on two wheels, this exploration day is a treasure waiting to be discovered by hikers and mountain bikers alike. Visitors to the Open Space during this activity are able to hike or bike to the West and East Sinks viewing areas.

Please review our Trail Tips page and FAQ page to prepare for this challenging hiking and biking opportunity.

All participants are required to check-in and complete their registration at the Portola Staging Area prior to accessing the trail system. Gates will open no earlier than 8 a.m. The West Sinks route is 6 miles round trip with a challenging hill climb while a visit to the east viewing deck is a strenuous 8 miles round trip and may take the majority of the designated activity time. Registration for this event is limited to 70 participants. Be sure to cancel your registration if you cannot attend, so that other participants can register. No walk-up registrations will be allowed.

This is a natural area characterized by certain inherent dangers including: mountain lions, rattlesnakes, poisonous plants and insects, weather extremes, loose rocks and rugged terrain. The Irvine Ranch Open Space contains rare and sensitive habitat and is under strict protection. Participants are required to stay on designated trails at all times. OC Parks Rangers may issue citations for visitors found off-trail. For your safety, please stay on the designated paths during your visit to Agua Chinon. To learn more about the staging areas and activity locations, please visit our Staging Areas Playlist page.

Other Important Notes:

• OC Parks Rangers require all trails to be cleared for closure by 1:00pm.
• No new trail users will be permitted onto the trails beginning one hour prior to closing.
• Dogs are prohibited on the Irvine Ranch Open Space. By nature, dogs are predators; their presence and their lingering scent disturb the indigenous wildlife and disrupt vital routines long after a dog has left the area.
• Minors, ages 18 and under, should be accompanied by a parent or guardian.
• Adult mountain bikers are requested to wear helmets. Minors are required to wear helmets per state law.
• Motorized recreation vehicles of any class or type are not permitted for use in the Irvine Ranch Open Space.
• Inclement weather or fire danger will cause the program to be cancelled.

Multi-use trail etiquette: Please remember that bikers yield to hikers when sharing the trails. Click here for more trail tips.

To minimize the human impact on wildlife and their habitat, there may be unannounced trail closures or the rotation of areas being open and closed. This is an adaptive management approach to accommodate both the human users and the wildlife needs.