On this project, Yerba Buena’s team demolished a timber retaining wall and replaced it with approximately 1,900 feet of new wall of drilled-in-place steel soldier beams and timber lagging.
The existing 10-foot-tall wall held back a hillside of sandy soil that provides habitat for sensitive species, including the locally rare California croton, San Francisco wallflower, and green hairstreak butterfly. The remnant sand dune area is so susceptible to erosion and the habitat is so sensitive that the Recreation and Park Department, which owns the land, discourages public traffic on the property.
One construction challenge was to build a new wall behind the old one while minimizing the impact to the habitat and avoiding construction loads on the old wall that would cause it to fail. We used an equipment bridging system with crane mats and temporary piling to displace the direct equipment weight away from the wall while minimizing the construction footprint.
Working on a steep slope right next to a private home presented challenges, as did maintaining stormwater pollution prevention plan control during wet weather. We conducted a preconstruction survey of the neighboring house to document existing conditions, and we performed weekly vibration monitoring and settlement surveys.
Subcontractor Granite Excavation & Demolition, Inc., did the demolition and wall construction.
After completing the wall, out team removed the old wooden wall, installed new signs and cedar fencing, graded, and installed erosion control features. Then we planted 3,000 native plants on the affected hillside areas to stabilize the dune and we provided a year of plant maintenance.
- Project Name: Funston Retaining Wall and Landscape Maintenance
- Category: Civil Construction
- Client/Owner: San Francisco Public Works/San Francisco Recreation and Park Department
- Location: San Francisco, CA
- Dollar Amount: $699,939
- Soldier pile retaining wall with timber lagging
- Sensitive plant and insect species
- Erosion control on steep slope next to housing
- Vibration monitoring
- Split-rail fencing
- Planting and landscape maintenance