Artificial reef site selection: geophysical surveys for San Clemente Kelp reef

Abstract

A critical component of artificial reef development is a thorough geophysical and geological evaluation of the potential reef sites. Artificial reefs are typically designed to: 1) enhance specific biological communities, and 2) maintain their structural and functional integrity for many years without: deteriorating or being permanently covered by sediment. In this context, having reliable and detailed ocean bottom characterization data is necessary to properly site and design artificial reefs. Southern California Edison is constructing the 150-acre San Clemente Artificial Reef in response to a California Coastal Commission/Marine Review Committee (CCC) Study, which determined that San Onofre Nuclear Generating Station (SONGS) was impacting a nearby kelp bed community. The reef is being designed specifically to grow giant kelp (Macrocystis pyrifera). The 22.4-acre experimental phase of the mitigation project was built in September 1999. A five-year study is now underway to determine and refine the best construction techniques, the best material type (either concrete or quarry rock) and the most effective reef material spacing on the bottom. Detailed geophysical and geological surveys were carried out in the siting phase of this project at eleven different potential kelp artificial reef sites between 1991 and 1998. Once the San Clemente site was chosen, even more detailed bottom characterization studies were performed to assure the successful placement of the San Clemente Artificial Reef. These surveys utilized a precision fathometer, side-scan sonar, and a subbottom profiler, as well as ground-truthing surveys. This work was done not only to assure the successful placement of the reef, but also as critical input to the design of the reef itself.