Alpine Road Regional Trail Improvement Project

Alpine Road Trail will be be open through the winter and spring of 2022-2023. Expect closures in the summer-fall of 2023 as work on Phase 2 of the project will begin.

Alpine Road Trail is a San Mateo County dirt road that runs approximately 2.3 miles between the end of paved Alpine Road above Portola Valley to the north and Page Mill Road near Skyline Boulevard to the south. It provides a valuable regional trail connection between Midpen’s South Skyline region preserves and trails down to Portola Valley and Woodside. Alpine Road Trail also travels partly through Midpen’s Coal Creek Open Space Preserve. It is a popular hiking, cycling, and equestrian trail, connecting the valley floor to a vast trail network. 

San Mateo County owns the right-of-way across the entire Alpine Road Trail. Midpen owns only a portion within Coal Creek Preserve, with the remainder located on private lands. Midpen has an easement to travel over this portion of the road (that is closed to public vehicle use) and used the trail for patrol, maintenance, and emergency access.   

In the mid-1990s, a large landslide eliminated a portion of the road, and was no longer accessible to vehicles. Erosion events and culvert failures in 2013-14 and 2016-17 further degraded the roadbed and continues to contribute sediment into Corte Madera Creek.   

Corte Madera Creek is a tributary to San Francisquito Creek. San Francisquito Creek and its main tributaries are designated as critical steelhead trout habitat by the NOAA and listed as sediment-impaired under the Clean Water Act. Sediment deposited in the streambed can smother their spawning sites and impair their ability to migrate upstream. Additionally, Choris’ popcorn flower and Western leatherwood, endemic to the San Francisco Bay Area, are both listed rare species by the California Native Plant Society. They depend on healthy riparian habitats and are threatened by erosion events. They are known to occur downstream at Searsville Lake and Russian Ridge Open Space Preserve. 

The Alpine Road Regional Trail Improvement Project was identified as a top 10 priority in Midpen’s community-supported Vision Plan. The project addresses two large failures and improves surface drainage to prevent further road degradation and to protect Corte Madera Creek. The repaired trail will re-establish Alpine Road as a regional trail connection in some areas while retaining a drivable section for critical fire and emergency access. 

Phase 1 of project was completed from summer to fall of 2022. It involved repairing the southern portion of the dirt road to a 12-foot road width from Page Mill Road to Meadow Trail. From Meadow Trail to Portola Valley, it converted Alpine Road to a 6-foot-width trail. Alpine Road will remain open between November 2022 and June 2023.   

Phase 2 of the project will take place in the summer and fall of 2023. Alpine Road Trailhead at Ciervos Road will be temporarily closed starting June 2023 to allow for construction of a Lower Alpine Road retaining wall project and create a new bypass trail to replace the existing informal bypass trail. 

The Alpine Road trail improvement project is funded through the 2014 Measure AA open space bond.  In addition, this project is made possible in part by a generous $272,211 grant award from Santa Clara County in June 2022. We appreciate our partnership with the County to complete this important project.  

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