Sampling of outer continental shelf shell mounds associated with platforms located in the Santa Barbara Channel and Santa Maria Basin.

Abstract

From the Summary: “This Feasibility Study represents the first step in the planning process for the OCS shell mound characterization sampling. Results of this feasibility study indicate that sampling of shell mounds centered directly beneath active platforms is not feasible at this time because of safety, cost, and scheduling concerns, and because of the limited information that would be collected when sampling only a single location on a shell mound. Consequently, it is recommended that platforms with shell mounds centered outside of the platform footprint (e.g., Gilda and Gina) be sampled from a vessel. Sampling from a vessel eliminates most of the potential hazards associated with sampling from a platform, enables the sampling of multiple locations and has a proven record of success. Other important   accomplishments/findings of this feasibility study include:

Selection of candidate platforms and representative shell mounds within the depth limitations of commercially available sampling equipment (e.g., <300 feet);

Selection of appropriate sampling equipment (vibracore) based on sampling goals (i.e., continuous cores up to 20 feet in length), identification of the limitations of alternative commercially available sampling equipment and demonstration of the experience required for the use of the selected tools for collecting sediment cores from shell mounds at comparable sampling depths.

Identification of specific locations on the platforms that can accommodate the required sampling equipment ( based on overhead height, isolation from overhead and overwater hazards) without significant risk to personnel or structures above the water surface and which provide access to a sampling point at or near the mound apex.

Identification of sampling limitations relating to capability of commercially available equipment and restrictions posed by platform structure and operations.

Identification of data gap regarding potential obstructions below the water surface for sampling of mounds centered underneath the platform superstructure and recommendation to address via (1) subsurface remote or diver assisted video reconnaissance survey; (2) diver survey within diver depths; and/or (3) live video during actual sampling operations.

Identification of two candidate platforms (Gina and Gilda) with shell mounds centered outside of the platform footprint and within the appropriate depth limitations (<300 feet) enabling sampling from a vessel.”