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Energy Commission Releases Preliminary Assessment of Rio Mesa Solar

Artist's conception, Rio Mesa solar project | Image courtesy California Energy Commission

The California Energy Commission (CEC) has released a portion of its Preliminary Staff Assessment (PSA) of the proposed Rio Mesa Solar Electric Generating Facility, and the CEC's staff has some issues with the project's impacts on the surrounding environment.

Part A of the PSA, released September 28, says that the CEC's staff need more information on the project's likely impact to paleontological, water, and visual resources before they can make an adequately informed assessment of the 500-megawatt concentrating solar project, proposed by BrightSource Energy for about 3,800 acres of land owned by the Metropolitan Water District southwest of Blythe in Riverside County.

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The paleontological and visual resources impacts would seem to be the largest issues of concern. BrightSource and the CEC staff have been wrangling over the exploration of the site's significant fossil deposits which the company should undertake. The fossil deposit, dating to the end of the Pleistocene, has already given up more than 800 vertebrate fossils including a fossilized tortoise burrow with eggs, a first in the paleontological world. The project's hundreds of thousands of heliostats that focus sunlight on two boilers will be mounted on pylons driven into the ground by means of vibration. Such vibration would destroy any nearby fossils.

CEC staff have asked BrightSource to provide a more thorough report on the location and size of the fossil deposits by December 3.

The project's effects on visual resources in the eastern California desert may prove harder to mitigate. As the PSA says:

The project in combination with existing and foreseeable future projects within the immediate project viewshed could contribute to significant unavoidable cumulative visual impacts. Project impacts, in combination with existing and foreseeable future solar and other development projects within the I-10 corridor in Riverside County, could contribute to a perceived sense of cumulative industrialization of the open, undeveloped desert landscape of the eastern Chuckwalla Valley and Palo Verde Mesa, and impact views of scenic resources as experienced by I-10 motorists, local residents, and recreational visitors within the Rio Mesa SEGF viewshed. Within the southern California desert as a region, anticipated cumulative operational impacts of past and foreseeable future region-wide projects are considered cumulatively considerable, potentially significant and unmitigable considering the substantial decline in the overall number and extent of scenically intact, undisturbed desert landscapes, and a substantially more urbanized, industrial character in the overall southern California desert landscape.

Part B of the PSA is due out mid-month. The CEC will then hold a public comment process including public hearings, after which a Final Staff Assessment will be published. The Commission will use that final assessment as staff testimony as it deliberates on the fate of the project. Commissioners have routinely voted to override CEC staff concerns about project impacts in the last few years of considering desert solar projects.

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About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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