Seafloor Hazards Survey, Santa Barbara County, California State Waters
Authors: Saade E.J. , Gaal R. 
Published: October 2008

In the summer of 1989, the California State Lands Commission contracted Sachse Engineering Associates, Inc. to perform a multisensor survey of the seafloor in California State Waters to locate and identify hazards to the local fishing interests. The purpose of thesurvey was to complete a Seafloor Hazards Analysis of all objects that may impact drag fishing nets and equipment. Search, location and identification of the anomalous objects was completed using a Side Scan Sonar. Marine Magnetometer and a Remotely Operated Vehicle.

The State Lands Commission intends to use the positive identification and location of these targets to, wherever necessary and possible, oversee their removal from the seafloor

INTRODUCTION

Sachse Engineering Associates, Inc. (S.E.A.) performed a multi-sensor geophysical survey and Remotely Operated Vehicle (ROV) investigationof portions of the seafloor for the California State Lands Commission (SLC) during the summer of 1989. The purpose of the survey was to investigate certain areas ofCalifornia State Waters within the Santa Barbara Channel that may contain seafloor features that are hazardous to local fishing operations.

The initial survey areas were destined based upon reports from the local fishing community of areas where fishing equipment had been either lost or damaged. The overall area of interest has historically been one of intensive oil-field exploration and development. All of the concerned parties have an interestin whether the eventual identification would tie the anomalous targets to oil-field development, local fishing activity or natural geological characteristics of the sea floor.

The project was designed as a three-phase study by the SLC. Phase I consisted otcollecting information about the seafloor, locations using state-of-the-art dual frequency side scan sonar and a marine magnetometer. Phase II was the interpretation and analysis of this newly collected data, combined with existing information from previous studies, to generate maps and select targets thatrequired additional identification. Phase III was designed to visually identify and precisely locate each target of interest using a ROV outfitted with a 35 mm camera, video and scanning sonar.

Five primary areas were selected for high-resolution dual frequency side scan sonar, magnetometer and visual inspection. The survey design parameters required that parallel track lines, spaced 300 feet (91.5 m)apart be surveyed over pre-determined lengths, varying between 600-15,000 feet. These survey lines were defined by boundaries. In addition, each area contained at least one confirmation tie-line. Theresulting total line mileage of the five combined areas was 180 statute miles. Geophysical instrumentation sensors operated simultaneously over each line included a dual-frequency side scan sonar, marine magnetometer and echo-sounder.

A total of 50 targets were identified as anomalous during the analysis phase of the study. These targets were prioritized for investigation and identification. During the ROV operations a total of 28 target siteswere investigated, only two of which were found to reveal no significant feature on the seafloor. At the remaining 26 sites, a total of 36 objects were identified by visual inspection using the ROV.