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Mitigation Projects > Artificial Reef > Experimental Phase

[Artificial Reef] Experimental Phase

  • Planning & Construction
  • Results & Recommendations from the Experimental Reef
map of locations of the experimental artificial reef off San Clemente

Planning and Construction

SCE submitted a preliminary conceptual plan for the experimental reef in June 1997, which was approved by the Executive Director of the Coastal Commission and forwarded to other state and federal agencies for review. As lead agency, the State Lands Commission (SLC) determined that under the requirements of CEQA a Program Environmental Impact Report (PEIR) should be prepared to evaluate both the experimental reef and the subsequent full mitigation reef. SLC began the environmental review process in March 1998, and certified the final PEIR and issued the offshore lease for the experimental reef on June 14, 1999.

The final plan approved by the California Coastal Commission was for an experimental artificial reef located off San Clemente, California that tested eight different reef designs that varied in substrate composition (quarry rock or recycled concrete), substrate coverage (17%, 34%, and 67%), and presence of transplanted kelp. All eight reef designs were represented as individual 40 m x 40 m modules that were replicated in seven areas (i.e., blocks) for a total of 56 artificial reef modules totaling 22.4 acres. SCE completed construction of the experimental reef on September 30, 1999.

Map showing the locations of the experimental artificial reef off San Clemente, CA and nearby natural reefs at Dana Point, San Mateo and Barn. Numbers in the inset represent the locations of the seven clusters of eight modules.
Experimental reef concrete module experimental reef quarry rock module
experimental reef concrete modulePhoto by Richard Herrmann Experimental reef quarry rock module. Photo by Richard Herrmann
satellite image of surface canopy of giant kelp

Results and Recommendations from the Experimental Reef

Five years of post-construction monitoring of the experimental reef were completed in December 2004. Results from the five-year experimental phase of the artificial reef mitigation project were quite promising in that all artificial reef designs and all seven locations (i.e., blocks) tested showed a near equally high tendency to meet the performance standards established for the mitigation reef. It was concluded from these findings that a low relief concrete rubble or quarry rock reef constructed off the coast of San Clemente, California has a good chance of providing adequate in-kind compensation for the loss of kelp forest biota caused by the operation of SONGS Units 2 and 3.

Satellite image showing the surface canopy of giant kelp on the 56 experimental reef modules of the San Clemente Artificial Reef (SCAR), and on the nearby natural reefs at San Mateo (SM) and San Onofre (SO). SM was one of two reference reefs used to evaluate the performance of SCAR. SO is the reef that is adversely impacted by the SONGS discharge plume. Image courtesy of Google
bat stars   spiny lobster
Bat stars foraging among young sea fans on the experimental reef. Photo by Richard Herrmann The spiny lobster Panulirus interruptus emerging from a giant kelp holdfast.
Photo by Richard Herrmann
oar kelp   sheephead wrass and kelp bass
The oar kelp Laminaria farlowii on quarry rock boulders.
Photo by Richard Herrmann
Sheephead wrass and kelp bass aggregating on a rock module.
Photo by Richard Herrmann

A final report on all the findings and recommendations gleaned from the experimental phase of the artificial reef project was prepared by UCSB scientists and submitted to the Executive Director of the CCC on August 1, 2005. These findings and recommendations formed the basis of the Executive Director’s determination that: (1) the mitigation reef shall be built of quarry rock or rubble concrete having dimensions and specific gravities that are within the range of the rock and concrete boulders used to construct the SONGS experimental artificial reef, and (2) the percent of the bottom covered by quarry rock or rubble concrete on the mitigation reef should average at least 42%, but no more than 86%. The Commission concurred with the Executive Director’s determination for the type and percent cover of hard substrate on October 12, 2005.