Synopsis: Ocean-floor seismic studies designed to pinpoint the earthquake faults near the Diablo Canyon nuclear plant will run the risk of major environmental impacts along the Central Coast, a new Draft Environmental Impact Report reveals. But a state law requires the studies of some kind to help determine the location, scope, and nature of the faults as well as the dangers they may pose to the aging plant and the many residents and visitors who would be exposed to an earthquake-caused accident at the plant.
Seismic studies are being planned later this year along the ocean floor across 530 square nautical miles from Cambria to Guadalupe just west of Santa Maria. The goal is to try to better assess the dangers that earthquake faults pose to the Diablo Canyon nuclear plant and, by extension, to the thousands of people who live in and visit the area and who would be exposed to an accident at the plant and its consequences, such as the release of radioactivity as happened with the Fukushima nuclear plant meltdown in Japan a year ago.
PG&E, the owner of the plant, is requesting $47 million to conduct the studies and other work from the California Public Utilities Commission. The studies are required by a state law adopted in 2006, and the California State Lands Commission has developed an environmental impact report on the proposed plan, which will be the subject of public hearings on Thursday, April 19, in the San Luis Obispo County Board of Supervisors chambers,, 1055 Monterey Street, San Luis Obispo. The hearings are scheduled for 2 and 6 p.m. on that day.
The draft environmental impact report (DEIR) states that the project would "generate potentially significant environmental impacts on air quality, terrestrial and marine biological resources, greenhouse gases (GHGs), land use and recreation, and noise." The impacts would stem from activities of a geophysical survey vessel, its associated survey equipment, and support/monitoring vessels within the project area.
The survey essel would tow a series of sound-generating air guns and sound-recording hydrophones along pre-determined shore-parallel and shore perpendicular transects, the DEIR said.
As a result, the Commission will consider the "no project alternative," an option required by the California Environmental Quality Act. If the Commission does not approve the project, two things could follow: one, PG&E would rely on, the DEIR said, "existing information and desktop analysis to assess features, movement and hazards." Or, two, the project could be modified to significantly reduce the impacts, if that is possible and still meet the needs of the study. (DEIR EXECUTIVE_SUMMARY)
The Independent Peer Review Panel (IPRP), an advisory group composed of a number of other state agencies and, as of a few months ago, San Luis Obispo County, has already proposed a reduction in the size of the seismic survey area, which is reflected in the DEIR. Second district supervisor Bruce Gibson, who has a doctorate in geophysics with a specialty in exploration seismology, is the county's representative to the IPRP.
He said the IPRP considers the overall seismic studies plan proposed by PG&E to have covered the appropriate geological targets. In recent months, the IPRP suggested eliminating the far northern part of the area originally proposed to be studied because the possible connection between the Hosgri and San Simeon faults there near San Simeon Point is well-enough understood that further high energy 3D work there is not necessary. Gibson said the reduction in that footprint for the studies cuts the time needed to gather the data by about 10 days. That would save funds and reduce environmental impacts due to a smaller area being studied.
The IPRP, however, may ask for further analysis of the survey method details. "The question," he said, "is whether we are doing the highest-quality survey. I want the discussion to be on whether we are getting a state-of-the-art survey for the specific questions we need answered."
He used this example to illustrate his point: "If we want to look inside the body, we can do it with an x-ray, a CAT scan or an MRI. We might say that PG&E is planning something like a CAT scan. I would like it clarified as to whether we need an MRI instead."
An IPRP meeting is scheduled on April 5 in San Francisco to discuss this and other issues surrounding the seismic studies, including possibly the amount of funding needed, how much PG&E and taxpayers should pay and the hiring of a contractor to conduct an analysis of the data developed from the seismic studies.
PG&E proposes to conduct the studies between next September and December
The DEIR said "PG&E’s geosciences staff believes that data gathered from the additional studies that comprise the project would improve characterizations of these fault zones and allow PG&E to refine estimates of the frequency and intensity of ground motion that is likely to occur in the area surrounding and including the DCPP (Diablo Canyon Power Plant). This information may also improve assessments of the potential seismic hazard at the (plant)."
During the survey, the DEIR said, an array consisting of 18 active air guns, divided into two subarrays, would likely be used. two additional acoustical data acquisition systems would be operated continuously from the survey vessel: a multibeam echosounder and a sub-bottom profiler.
Geophones would be placed in the nearshore area, in water depths of up to approximately 66 feet (20 meters) using a vessel and, in some locations, divers. For the nearshore survey area, where it is too shallow for towed arrays, geophones would be placed on the sea floor by hand to record seismic responses from on- and offshore seismic sources. Lines of disc-shaped geophones strung together on cablesmwould be placed on the seafloor along the approximate routes depicted in Figure ES-4. PG&E estimates that it will deploy approximately 600 geophones for the project."
In the northern part of the study area, activities would include the temporary placement of 6-inch-high and 5-inch-wide, nodal (uncabled) receivers in agricultural areas and alongside roads, including Route 1 . . . trucks and vehicles would be used to service (them).
The DEIR found significant and unavoidable impacts to fin, humpback and blue whales resulting from noise. Substantial interference in the movement of any native resident, such as the Morro Bay stock of the harbor porpoise, is also considered to be significant; based on this threshold, the project’s impacts on the Morro Bay stock of the harbor porpoise are expected to be significant and unavoidable, and the same for sea otters.
For commercial fishing, the DEIR said, the project impacts could be cumulatively significant because the additional low-energy seismic survey planned by PG&E contribute to the significant disturbance in the project area. By adding to the seasonal disruption, more fishing activity is likely to be impacted. The disruption would occur at a time that the local commercial fishing industry is in transition towards establishing a sustainable fishery. Cumulative effects are potentially significant because the local commercial fishing industry has been weakened by other factors, and the proposed seismic surveys may contribute to multiple disruptions over consecutive seasons (2011 and 2012).
The Commission has identified the following known areas of controversy/issues to be resolved regarding the proposed project:
-Technical design of the survey to address potential seismic hazards in the project area, including:
o The geographic scope of the study, including how close to shore to run survey track lines;
o The specific types of studies to conduct (e.g., high-energy deep seismic, high mresolution swath bathymetry, core-sampling, etc.);
o Whether the current footprint of the study is sufficient to provide meaningful mdata on the intersection of specific fault zones (e.g., the Hosgri and Los Osos
Faults, and the southern terminus of the Shoreline Fault); and the most appropriate technology for analyzing the fault zones.
--Potential to harm marine mammals and other marine biological resources.
--Long-term impacts on fish and commercial fishing.
--Survey activity and air gun noise in marine protected areas.
