An Update on Santa Cruz Water

wikimedia commons

Last October the City of Santa Cruz Water Supply Advisory Committee (WSAC) held an open call for citizen ideas about how to address our water shortfall. This culminated in a day long ideas convention during which over 50 proposals were presented, from recycled water, to quarry storage, to even pulling water out of the ambient air. Following the event we allowed for online rating of these proposals via our platform at civ.io/santacruzwater, providing people with an unparalleled opportunity to help decide how to solve our water problems.

The ideas considered during that event haven’t disappeared into the ether, they have instead been put through a rigorous decision making model and underwent heavy means testing for technical feasibility. Now, 10 months after the initial convention, WSAC has developed a series of “portfolios” of potential water supply options that outline the preferred strategies for dealing with the now agreed upon 1.3 billion gallon shortfall. This number, for those of you are wondering, was arrived at through assuming a prolonged drought (up to 8 years for the purposes of planning), and by assuming net water use in the city will either stay close to what it is now or decline further.

At the heart of these portfolios are two strategies that are still largely unproven, but should they work, are considered by all members of the 12 person committee to be the preferred options. These options are “in lieu” aquifer recharge, which would mean that the Santa Cruz Water Department would provide water to either the Scotts Valley Water District or Soquel Creek during the winter months when we have excess water, allowing them to not draw water from their own aquifers; and Aquifer Storage and Recovery (ASR), which would mean direct injection of potable water into the aquifers. The reasons why these are still largely unproven strategies is because aquifers vary widely in their porous makeup and hydrology, and in the case of in lieu storage, the Newell Creek Dam would have to be raised and a second pipeline constructed. All of the portfolios also include full implementation of additional conservation measures, but even in the best case scenario these are estimated by the city to only reduce water use by 200 million gallons a year.

Should these preferred options prove unsuccessful or infeasible, each portfolio has a backup supplemental supply option. These include the use of recycled water that would require building a new plant, buying desalinated water from the Deep Water Desal plant expected to be built in Moss Landing, or building our own desalination plant. For recycled water use there are two options, indirect potable reuse, which would take treated sewage and cycle it into Loch Lomond, with us pulling it up from the other side after it blends in with reservoir water; or direct potable reuse, which is exactly that, treated sewage being directly introduced to the water system. Both instances of recycled water use have proven effective, and safe, however direct potable reuse is still not legal in California, though it is expected to be within 5 years.

Below are the 6 portfolios of water supply options being considered by the committee. They vary in their strategies and triggers for backup plans, and all include conservation. Their total estimated capital costs have also been included. Vote and comment on the portfolios and your input will be shared with the committee.

Water Supply Portfolio 1.1
In lieu recharge of aquifers in Scotts Valley and Soquel areas with a Newell Creek Dam raised to support an extended season for in lieu service. Plan B entails indirect potable reuse of purified recycled water by pumping it back to Loch Lomond as a fallback should in lieu recharge prove unsuccessful. 8 year trigger before using indirect potable reuse.



Water Supply Portfolio 1.2
In lieu recharge of aquifers in Scotts Valley and Soquel areas with reduction of annual carry over storage from 1 billion gallons to 500 million gallons to support an extended season for in lieu service, does not include the raising Newell Creek Dam, but dependent upon water rights. Indirect potable reuse of purified recycled water back into Loch Lomond on an 8 year trigger is still the fallback option in case in lieu service fails to materialize.



Water Supply Portfolio 2
Aquifer storage and recovery (ASR) with injection wells into the aquifers at Scotts Valley and in the Soquel areas. If ASR proves unsuccessful, build a recycled water facility for direct potable reuse, dependent upon the state making it legal.



Water Supply Portfolio 3
Aquifer storage and recovery (ASR) with injection wells into aquifers at Scotts Valley and Soquel Creek in parallel with creation of sea water barrier with purified recycled water, so a recycled water facility is assumed. Direct potable reuse of recycled water as the fallback plan should ASR not work.



Water Supply Portfolio 4.1
Aquifer Storage and Recovery (ASR) with injection wells into aquifers at Scotts Valley and Soquel Creek in parallel with desalinated water from Deep Water Desal to use as an accelerator of aquifer recovery. The back up plan should ASR not work is to completely use water from Deep Water Desal after an 11 year trigger.



Water Supply Portfolio 4.2
Aquifer storage and recovery (ASR) with injection wells into Scotts Valley and Soquel Creek in parallel with desalinated water from a locally constructed desalination facility to use as an accelerator for aquifer recovery. After an 11 year trigger, should ASR not work, the local desalination plant would be the backup plan.



 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: