January 2023 Emergency Storm Repairs, Debris Management & Laguna Repair

January 2023 Emergency Storm Repairs, Debris Management & Laguna Repair

On January 4, 2023 Governor Newsom proclaimed a state of emergency throughout California to support the ongoing response to recent winter storms. Due to the recent rains, excess woody debris had accumulated in Pescadero Creek and Cordilleras Creek. At Pescadero Creek this debris was obstructing and deflecting streamflow causing erosion at the bridge abutment. The purpose of this emergency work was to protect the bridge abutment from further scour and potential flooding. For the duration of the Project, materials and equipment (Gradall) were positioned on the paved roadway and shoulder. Equipment access to the creek channel was not required. The Gradall bucket and a chain was used to clean pluck accumulated debris from the channel. At Cordilleras Creek rains on 12/31/2022 caused debris blockage of existing trash racks which caused the creek to over top and flood the surrounding facilities. The purpose of the emergency debris removal work was to eliminate active flooding during the 12/31/2022 event and to prevent flooding at the facilities with the future storm forecasted for the upcoming week (1/4/2023). Initially debris was removed on 12/31/2022 by an on-site excavator. Equipment did not enter the creek channel. Debris removal continued by hand on 1/2/2023 at the trash grate area and at an accumulation area located approximately 100 feet upstream on 1/3/2023. Only the minimum amount of work necessary to restore flow and alleviate flooding was conducted. There was no channel modification or fill. Additionally, a slip-out occurred on Laguna Dr., 0.6 miles east of Hwy 84. The eroded area at the slip-out will be reconstructed with rock, back-filled and capped with soil, and revegetated. Heavy equipment would be operated from the roadway. Following construction of the bioengineered slope, the upper portion of the repair would be covered with several inches of soil and hand seeded with a native plant mix. Post-construction erosion control BMPs would be installed to conserve soil resources and protect water quality. Sterile rice straw would be placed over the soil and covered with natural fiber jute netting, and/or hydro mulch and seeded with native seed. Work will be conducted using best management practices detailed in the County of San Mateo Routine Maintenance Program Manual.

San Mateo

Northern California

San Mateo