Address
7th and 8th Avenues between Moraga and Ortega Streets, San Francisco, CA
Year Constructed
1991
Structural Engineering Firm(s)
Structural Engineer(s)
Architect(s)
N/A
Main Contractor
Malcolm Drilling
Media
7th/8th Avenue Slope Stabilization Retaining Wall
7th/8th Avenue Slope Stabilization Retaining Wall
Source: Google Earth
7th/8th Avenue Slope Stabilization Project Extents
7th/8th Avenue Slope Stabilization Project Extents
Source: Google Earth
7th/8th Avenue Slope Stabilization Project at Completion
7th/8th Avenue Slope Stabilization Project at Completion
Source: John H. Hom
Structure Description

The 7th/8th Avenue slope stabilization project consists of two retaining walls. A 1300-foot long retaining wall runs behind the houses along 8th Avenue. A 375-foot long retaining wall runs behind the houses along 7th Avenue.  The retaining walls consist of steel soldier piles, tiebacks, and sprayed on concrete (shotcrete or gunite).

Significance to Structural Engineering History in Northern California

Following the 1989 Loma Prieta earthquake, the soil slope between 7th and 8th Avenues became unstable.  Houses on 8th Avenue (the uphill slope) faced demolition if the slope could not be stabilized. Additional houses on the downhill slope on 7th Avenue also faced damage if the soil continued to move. Taking two years to complete and working on very steep terrain, SOHA Engineers and Malcolm Drilling stabilized the soil by driving steel soldier piles deep into the slope and retaining the soil with concrete retaining walls.  The project saved over forty houses on 7th and 8th Avenues.

Awards
  • NCCA Ted Van Midde Memorial Excellence in Concrete Award
  • City and County of San Francisco Board of Supervisors Certificate of Honor
Interesting Facts
  • The 1300-foot retaining wall is the longest in San Francisco.
  • The elevation change from 8th to 7th Avenues is 100 ft, for an average grade of 33%
Related Event(s)