Desalination In Santa Cruz

Posted by Jon Winston 
 
Someone once described a commercial desalination plant as one where you pour money in one end and you get clean water out the other. (Then again, we happily pay $8/gallon or more for bottled drinking water and have all that plastic waste to deal with after.) Our speaker today, Heidi Luckenbach of the Santa Cruz Water Department, helped put it all in perspective. Ms. Luckenbach explained our area's need for a supplemental drinking water supply and why "desal" is a viable choice.
 

The Santa Cruz and Soquel Creek Water Departments have joined forces to develop an integrated water plan to address the drinking water shortage affecting both districts.  

Together, the Santa Cruz and Soquel systems service about 135,000 customers.  Santa Cruz gets about 95% of it's water from surface sources (25% of which is from up north on HWY 1 and 75% from the Loch Lomond reservoir) and 5% from wells in in Live Oak.   All of the Soquel Creek water is from the creek.  

Santa Cruz uses 10-12 million gallons per day (MG/D).  The Soquel Creek system serves about 1/2 the population of Santa Cruz and uses less than half the water (4-5 MG/D).

Given our current reserves, the amount of existing above ground and subterranean water, and our production capacity we would have to cut back by at least 50% if we experienced another drought like we had in 1976-77.   Furthermore, if we continue to overdraft our underground sources saltwater intrusion will become a major problem.

A comprehensive 4 point plans has been developed to address our short to medium term water issues:

  1. Conservation.  A realistic target of reducing annual consumption by 300 MG/Year as been set.  Santa Cruz customers average 65-77 gals/day, almost half of the statewide average of 130 gals/day.  That's good, but we need to do more.
  2. Institute mandatory cutbacks of at least 15% during droughts
  3. Use recycled water where possible (mostly irrigation).
  4. With the above 3 measures, we still fall short.   Soquel Creek will still need upwards of an additional 1 MG/D.  Santa Cruz will need as much as 1.5 MG/D during summer and drought periods.   Hence, the final point in the plan is to create a supplemental supply source - a 2.5 MG/D capacity desalination plant.  

Desalination was arrived at after investigating other possible solutions including: increasing storage capacity of existing reservoirs, building new reservoirs and tapping additional above and below ground sources.  The most attractive solution turned out be desal.  

There are a number of concerns related to desalination that are being studied.  These include: Water quality, Intake source and its effect of the bay, The amount of energy required to operate a desal plant, and brine discharge and its effect on the bay. 

A pilot plant with a capacity of 50 gallons/hour has been constructed at the Long Marine lab on the West Side to investigate the viability of a full scale plant in our area.  The pilot plant is currently operating and will continue to gather data through March 2009.  If all goes well, the SC and Soquel Creek Water Districts will jointly build the 2.5 MG/D plant at an estimated cost of $30M - $100M with completion in 2014.  

Visit the project's website at http://www.SCWD2Desal.org for additional details.