The L5A Levee project required the installation of a 200-foot-long by 3-foot-wide by 65-foot-deep cement-bentonite infill slurry wall to connect two existing slurry walls in the area of Pump Station 10 on the American River as part of the American River Common Features project. The purpose of the slurry wall installation was to improve the flood protection rating to a 200-year storm event.
Work included design of a pump bypass system around the slurry wall and design of a vertical shoring system for the excavation of the pump system. NV5 observed the excavation of an approximately 65-foot depth and determined the cutoff elevation. During excavation, we performed logging and sampling of the excavated native soils and performed field and laboratory testing of the soil and cement-bentonite slurry materials. Tests included permeability, specific gravity, viscosity, unconfined compressive strength, gradation, and unit weight.
During construction, NV5 performed welding inspection and compaction testing of subgrade soil and aggregate base rock by sand cone and nuclear gauge for the reconstruction of the levee top.