Environmental Improvements Proposed for Intake and Outfall Systems

Wedgewire screens protect 99.98% of all marine life.
Wedgewire screens and brine diffuser makes HB Desal Project environmentally benign.

Poseidon Water has proposed to use state-of-the-art wedgewire screens that have a width of one millimeter, which is narrower than the thickness of a dime or a credit card.  No fish can get through the screens and only two marine larvae would be impacted for every one thousand gallons of seawater withdrawn.  9,998 of every 10,000 marine larvae at risk of entrainment in the area of the screen will be unaffected.  There are no threatened or endangered species that would be at risk and no measurable impact to any Marine Protected Area (MPA) species.

The velocity of water drawn through the screens is less than a half-foot per second.  That velocity is so slow that “impingement,” or the chance of any marine life being pinned against the screen, would be completely eliminated.

Brine diffuser reduces concentrated seawater impact.

Natural seawater is 3% salt.  The concentrated seawater discharged by the desalination plant is 6% salt.  Thanks to the brine diffuser technology, within 46 feet of the outfall pipe, brine salinity will be within two parts-per-thousand (2 ppt) of ambient seawater.  The total area of the seafloor impacted by the slight increase in salinity will be 0.15 acres.

Independent scientists determine seafloor infiltration gallery "infeasible".

At the request of the California Coastal Commission, a team of independent scientists spent nearly two years studying the feasibility of building a seafloor infiltration gallery (SIG) to draw the seawater in from below the ocean floor.  After determining that the SIG would result in “severe” environmental and social impacts as well as add an additional $1.1 billion to $1.5 billion to the cost of construction, the Independent Scientific Technical Advisory Panel (ISTAP) reported to the Coastal Commission that a SIG at this location would be infeasible.
Download the ISTAP Report.
Download the ISTAP News Release.