FINAL REPORT Evaluation of Seawater Desalination Projects ...

EVALUATION OF SEAWATER DESALINATION PROJECTS
PROPOSED FOR THE MONTEREY PENINSULA
that intake and discharge permits are not required for the SDV, other material submitted by
the Water Standard Company suggest, and our belief is, that they will be required and are key
permits needed to operate.
Seawater Intake System
The SDV proponent calls its seawater intake system a “Multi-Depth Intake Anti-Entrapment
System.” The intake system consists of three elements. The first element is its ability to
move the intake and target non-sensitive areas. The proponents state that the SDV would be
stationed about five miles offshore where the intake pipe could be lowered into deep water
below the penetration of sunlight. The upper surface waters within the light penetration zone
are generally expected to support the most abundant and diverse aquatic communities. A
second key element of the intake system is that the lower portion would be equipped with
one or more EPA Regulation “Johnson-type” well screens with slot sizes small enough to
minimize entrainment of marine organisms. The implication is that sufficiently small screen
could be used to prevent significant entrainment of aquatic organisms. The third key element
was stated to be design of the system so that it would have a low hydraulic head and low
intake velocities (i.e., less than 0.5 fps). Intake velocities less than 0.5 fps are generally
expected to prevent significant amounts of impingement of aquatic organisms against the
intake screens. The above three elements are intuitively attractive, but insufficient
information is provided to evaluate whether the proposed Multi-Depth Intake Anti-
Entrapment System will achieve acceptable performance criteria or if these are merely the
goals for the system 20 .
Similar to on-shore plants, the intake system is expected to require a SWRCB permit to
withdraw water provided it operates within State and U.S. waters. Because the ship could be
readily moved, it is anticipated that one of two approaches would need to be met in order to
receive approval to withdraw extensive amounts of seawater: (1) demonstrate that the design
of the intake system is sufficiently forgiving that it could be deployed in almost any location
without concerns of environmental impacts, or (2) delineate ocean conditions and marine
communities in sufficient detail, including on-going monitoring programs, in order to define
a range of environmental conditions where the intake system would be allowed to operate.
The ability to move the SDV and change the depth of the Multi-Depth Intake Anti-
Entrapment System away from sensitive areas is stated as a benefit, but the proponent will
also likely be required to demonstrate how engineering and operational controls will prevent
the operators from accidentally moving the SDV and its intake system into sensitive areas
that may not follow assumed generalizations regarding ocean conditions. This may require
extensive marine studies and engineering design studies. While not necessarily
20 Proponent’s comments on the draft GEI/B-E report state: “The intake would be designed for a half foot per
second intake velocity using a 1 mm EPA 316B compliant well screen with blowback. … there are literally
hundreds of intakes operating the USA using these same criteria and therefore they are not goals at all. They
are legitimate design criteria."
Monterey Peninsula Water Management District 3-19