Wide-Area Debris Field and Seabed Characterization of a Deep Ocean Dump Site Surveyed by Autonomous Underwater Vehicles

This studypresents an analysis of a wide-area side-scansonar survey conducted with autonomous underwater vehicles (AUVs)at a deep water dump site in the San Pedro Basin, California. Disposal of industrial and hazardous waste in the oceanwas a pervasiveglobal practice in the 20th century. Uncertainty in the quantity,location, and contents of dumped materials underscores ongoing risksto marine ecosystems and human health. This study presents an analysisof a wide-area side-scan sonar survey conducted with autonomous underwatervehicles (AUVs) at a dump site in the San Pedro Basin, California.Previous camera surveys located 60 barrels and other debris. Sedimentanalysis in the region showed varying concentrations of the insecticidalchemical dichlorodiphenyltrichloroethane (DDT), of which an estimated350-700 t were discarded in the San Pedro Basin between 1947and 1961. A lack of primary historical documents specifying DDT acidwaste disposal methods has contributed to the ambiguity surroundingwhether dumping occurred via bulk discharge or containerized units.Barrels and debris observed during previous surveys were used forground truth classification algorithms based on size and acousticintensity characteristics. Image and signal processing techniquesidentified over 74,000 debris targets within the survey region. Statistical,spectral, and machine learning methods characterize seabed variabilityand classify bottom-type. These analytical techniques combined withAUV capabilities provide a framework for efficient mapping and characterizationof uncharted deep-water disposal sites.