Environmental assessment of proposed seawater desalination plant

The California Coastal Commission, an independent, quasi-judicial state agency with responsibility for regulating the use of land and water in the coastal zone, has recently published what amounts to an environmental assessment of a proposed new 50 million gallon per day seawater desalination plant on the site of a soon-to-be-closed power station that is already drawing and discharging ocean water for cooling purposes. The report is an extremely detailed assessment of the proposed project, likely one of the more detailed assessments of a seawater desalination plant ever published.

The plan was to use the existing infrastructure for withdrawal of water from the ocean as an input to the desalination plant. The report by the Commission staff finds that use of the open water intake will result in significant adverse effects to marine life, capturing more than 80 million fish larvae, eggs, and invertebrates each year that originate in areas along about 100 miles of shoreline, including areas within Marine Life Protected Areas. The desalination plant, using a reverse osmosis type of technology, would also discharge effluent with salinity concentrations that are harmful to marine life, and cause adverse direct and indirect effects on wetlands on and near the project site.The report is proposing that a new water intake be constructed below the ocean floor so that marine life is not sucked into the plant. Media reports indicate that the proponent is not happy with this recommendation.

While this assessment report is specific to a plant proposed for southern California, it provides an interesting framework for those assessing projects which involve extraction of large amounts of water from oceans or lakes. In addition to the impact of withdrawals and discharges on aquatic organisms, sections of the report deal with:

  • Wetlands and environmentally sensitive habitat areas
  • Flood, tsunami, and sea level rise hazards
  • Geologic hazards
  • Climate change
  • Public access and recreation
  • Land use – site designation and allowable uses

The report is available at http://documents.coastal.ca.gov/reports/2013/11/W19a-s-11-2013.pdf  The proponent’s website, describing and promoting the desalination facility, is at http://hbfreshwater.com/

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