
For the Golden Gate National Parks Conservancy
Mt. Tamalpais State Park, Marin County, CA
Completed: 2009
Campbell Grading Inc. was selected to design and construct the new multi-use (equestrian, hikers, runners, and mountain bikers) trail, which added a new section to the Bay Area Ridge Trail. The trail runs from Highway 1 (Pacific Way Intersection) for 1.5 miles northeast through California State land along the ridge to the Panoramic Highway. The ridge allows panoramic views of the Pacific Ocean, Farallon Islands, Frank Valley, Muir Beach, and the Redwood Creek Watershed (home to the Coho Salmon). The trail shares the area with bobcats, California black tail deer, coyotes, mountain lions, and a large variety of birds (e.g. nesting hawks, quail, etc.). Dias Ridge is named after Portuguese dairy ranchers and the trail head is located adjacent to a historic milk barn built by these Portuguese settlers.
The Dias Ridge trail historically followed an old fire road along the nose of the ridge. The road channelized water and sediment straight into Redwood Creek, creating gullies over 5' deep. This project is part of a larger effort to restore Redwood Creek to a healthier state for spawning Coho salmon. Campbell Grading, Inc. decommissioned the road and brought in over 7,000 c.y. of soil, in order to fill the deficit amount of soil lost to erosion and reestablish the ridge back to its natural watershed and drainage patterns.
The 1.5 miles of trail was designed and constructed to address the large elevation change (approx. 1000') while maintaining a maximum of 10% grade for the multiple types of users. Where the slope did not allow the 10% grade, sutter walls were constructed as a retaining method. The trail is designed to maintain the natural watershed drainage with techniques that eliminate sediment delivery to Redwood Creek. These methods include: out-sloped tread, drain lenses, wet water crossings, and reverse grades. The longest section of sutter wall is 110 linear feet ranging between 4' and 7' in height. In addition, a 22' length bridge and a 5' wide bridge was designed and constructed to span a tributary into Redwood Creek at the trail head. This bridge is designed for loads up to 5,000 lbs.
Throughout construction a large amount of native vegetation was carefully salvaged for re-vegetation. A large quantity of erosion control was installed as a part of this restoration process.