For this work, we documented subsurface geotechnical conditions for several levee systems by reviewing existing subsurface data and documentation of past levee performance. We also performed geotechnical explorations, including cone penetrometer testing, vane shears, and rotary borings drilled to depths of up to 70 feet.

Our Rough & Ready Island Study Area includes non-Project, urban levees that protect Port of Stockton facilities along the Deep-Water Channel. Sitting at the edge of the Delta, the 5.6 miles of levees protecting Rough & Ready Island are frequently loaded from tidal fluctuations and are underlain by organic soils along the western end of the island. The levees along the Deep-Water Channel are subject to erosion from waves caused by wind and ship traffic. Shannon & Wilson utilized existing and new subsurface explorations and laboratory testing, compilations of past performance, construction records, and historical accounts to identify analysis reaches and develop soil properties for modeling. Shannon & Wilson analyzed levee stability, seepage, erosion, and seismic characteristics for the Rough & Ready Island Study Area and developed remedial alternatives and performed analyses of conceptual remediated conditions.