The canyon separates the Conejo Grade area and westernmost Simi Hills from the Mount Clef Ridge to the east. It was formed by Arroyo Conejo (creek) flowing down through the Simis from the higher Conejo Valley to the lower Santa Rosa Valley, where the creek merges with Arroyo Santa Rosa and becomes Conejo Creek.[1]
It is located in an area locally known as La Barranca (Spanish for canyon).[2][3]
It is a deeply eroded canyon at the foothills of dramatic ridgelines and volcanic outcroppings[4] on the Mount Clef Ridge. Hill Canyon is part of the Conejo Canyons Open Space, which is owned and operated by the Conejo Open Space Foundation (COSF).[5]
The canyon is situated east of the Conejo Grade in Camarillo, CA, and is immediately west of the Mount Clef Ridge of Wildwood Regional ParkinThousand Oaks. Once slated for a golf course, the canyon is now protected open space.[6] Hiking trails and bridges are accessible from trailheads found for instance in Wildwood Regional Park, Rancho Conejo Playfields and Santa Rosa County Park.[7] Hill Canyon Trail is the primary trail and connects to the Hawk Canyon Trail, Western Plateau Trail, Arroyo Conejo Trail, Lynnmere Trail, and the Canyon Overlook Trail, which climbs to the top of the Mount Clef Ridge from Santa Rosa Valley.[8][9][10]
The only developed area in Hill Canyon is the Hill Canyon Wastewater Treatment Plant (HCTP),[11] which takes up about sixty acres and includes the largest bodies of water in Newbury Park. It has a capacity of 14,000,000 gallons per day,[12] and approximately 3.7 billion gallons of water are conveyed here every year for processing.[13] Thousands of gallons in sewage spills have led to leaks into the adjacent Conejo Creek, which discharges at its estuaryinMugu Lagoon.[14][15]
