Sheet Pile Wall: Overtopping Study Unocal, Guadalupe Dunes Oil Field Santa Maria, California

Coastal Environments was retained by Group Delta Consultants to evaluate beach characteristics and to generate beach profile designs in relation to stability assessment of the Guadalupe Dunes sheet pile wall. The design profiles were utilized in the computer program, RBREAK, to estimate run-up and overtopping in relation to the wall.

The Guadalupe Dunes Oil Field lies easterly of and extends down onto the alluvial plain of the Santa Maria River. A contaminant plume has been contained by installation of an HDPE wall. Unocal constructed a 360-foot-long steel cantilever sheet pile wall to protect the existing HDPE wall from becoming breached by discharges from the Santa Maria River.

The primary purpose of this study was to satisfy the Coastal Development permit requirements pertaining to the stability of the sheet pile wall during proposed excavation activities. The goal was to prevent the release of hydrocarbons into the environment in the event of overtopping, flooding, or failure.

Beach profile data were used to evaluate berm height, beach-face slope, beach width, and the effects of major storm events on the beach in the project vicinity. Aerial photographs were also reviewed to evaluate the seasonal migration of the Santa Maria River.

The run-up model, RBREAK, was initialized with a 60 minute long, simulated random wave time series representing wave conditions in 46 feet water depth for two design storms and the 100-year synthetic design storm. Three representative water level elevations were used in the computations. Two beach profile configurations were also considered. The sheet pile wall was approximated by using a slope of 52:1. The maximum over-topping rate and the average over-topping rate over a 60-minute period were calculated.

Client:

Group Delta Consultants

Client Contact:

Walter Crampton, PE
4455 Murphy Canyon Rd.
Suite 100
San Diego, CA 92123