980/1000 Ignacio Boulevard Creek Bank Stabilization Project

980/1000 Ignacio Boulevard Creek Bank Stabilization Project

The Project will remove about 731 square feet (sq ft) of unpermitted concrete fill from five Project site locations (Sites 1, 2, 3, 5, and 10) and restore the banks along Igancio Creek (Creek) utilizing a combination of biotechnical stabilization and riparian plantings. Project resetoration and stabilization activities include the following: Site 1 - A concrete wall will be removed and the south bank will be regraded to a two horizontal to one vertical (2:1) slope using native or clean soil material. New rock slope protection (RSP) will be buried below grade at the toe of the bank for stabilization and two temporary access paths will be installed at Site 1 to access Sites 2, 3 and 5. Site 2 - A concrete debris wall will be removed and the five surrounding California bay trees (Umbellularia californica) will be protected. Sites 3, 5, and 10 – Concrete debris will be removed at sites 3 and 5 and a three-tiered concrete wall at site 10 will be removed by excavation. The existing bank will be restabilized by installing a Crib Wall and interplanting the wall with willows for natural biotechnical stabilization. New RSP will be installed below grade at the toe of the bank and will serve as the foundation of the Crib Wall to help prevent undercutting. The Crib Wall will consist of stacked 0.75-foot-diameter riparian, untreated logs with the first log level utilizing rootwads as anchors when placed into the Creek bank. Logs will be secured together with bearing plates, rods, and reinforced with native clean soil placed within and behind the wall cavities. The area above the crib wall on the upper channel will be back filled and graded to a maximum 2:1 slope. Live willow stakes will be placed throughout the Crib Wall gaps to help anchor the wall to the Creek banks. A 36-inch diameter coast live oak tree (Quercus agrifolia) and root structure on the downstream edge of the Crib Wall at Site 5 is planned to be protected in place and has been accounted for in the Permittee’s tree mitigation. One 10-inch and one 24-inch California bay tree will be removed at Site 10 to allow for Crib Wall installation. As mitigation, 1,387 sq ft of temporarily disturbed areas will be hydroseeded with native plants and 107 sq ft of additional loose concrete debris will be removed. Tree planting mitigation will include nine coast live oaks, three bay trees, four buckeyes, and several willows interplanted within the Crib Wall. All Sites - All unpermitted concrete debris fill (731 sq ft) will be removed from the five Project site locations and properly disposed at an approved waste facility. If dewatering is needed, cofferdams made of gravel filled bags will be installed upstream and downstream of the work area and a bypass pipe will be used to reroute surface water to a stabilized area with proper erosion control protection. After final grading is completed, biodegradable erosion control fabric and entrenched fiber rolls will be installed on the bank slopes with wooden stake fasteners. All temporary disturbed areas will be returned to pre-project conditions and planted with native vegetation or reseeded.

Novato

Marin

San Francisco Bay Area