Mar 5 2014
In a prior blog I briefly mentioned the work done by Pat Mulroy and the
Southern Nevada Water District (SNWD).
In 1922, Nevada was allotted only 300,000 acre feet compared to California’s
4.4 million acre-feet. Who would have guessed that when the Colorado River
Compact was signed, Las Vegas population would explode from 5000 in 1922, to
two million residents currently.
So, what did the water managers do? Did they limit the growth of Las Vegas?
No. That tactic has been tried before in other communities and failed. What
Ms. Mulroy and the SNWD did was to do more with less. Currently Las Vegas
relies on Lake Mead for 90% of the water consumed, but they have done what
all other water-using communities need to do..they recycle their water,
returning 92,000,000 gallons per day via the Las Vegas Wash back into Lake
How is this possible? The Las Vegas sewage treatment plant is a tertiary
treatment plant, meaning the plant treats incoming sewage in two more
additional steps compared to the Point Loma Treatment Plant in San Diego.
The latter plant only takes the chunks out and little else and then dumps
the effluent about two miles out into the ocean. Primary treatment only.
Living on waivers from the Environmental Protection Agency for decades, San
Diego may not be granted a new waiver when it comes up for renewal.
The process name for the method used by SNWD is Indirect Potable Recycling
(IPR). Because they are actually adding water to Lake Mead they are allowed
to draw more than their 300,000 acre-foot share of the Colorado River flow.
Whoa! Do I mean that San Diegans may actually be drinking reclaimed Las
Vegas sewage? Absolutely. A molecule of water flowing into Lake Mead does
not know its destination, so yes, it can wind up flowing into the pipelines
that provide water via the San Diego County Water Authority (SDCWA). And by
the way, that water that flows to Lake Mead via the Las Vegas Wash is likely
cleaner than the Colorado River water that the SDCWA treats and then
disburses throughout San Diego County. For more information on this process,
see http://www.cleanwaterteam.com/interactive_prcs_map/water-reclaimation-project-files/presentation.html .
If that works for Las Vegas and the SNWD, why isn’t the SDCWA pursuing the
same proven way to do more with less. I am told its money. There is a saying
in the water business, “water flows uphill to money”, and it was never
truer. That’s why State Water Project water is pumped higher than the Eiffel Tower stacked on
top of the Empire State Building to move water over the Tehachapi Mountain
Range from the Delta to Southern California. Money did it.
How much will it cost to design and construct an IPR system and
infrastructure for San Diego County? Estimates are in the range of two to
three billion dollars. When completed 100,000,000 gallons per day can be
moved through the Pt. Loma Plant to the San Vicente Reservoir. Between the
latter system and the Carlsbad desalination plant, San Diego would be on its
way to water independence at the rate of 150,000,000 gallons per day.
Currently San Diego’s consumption is around 500,000 acre-feet annually.
Recycling plus desalination would supply about a third of San Diego’s water
needs at a per capita water use of 150 gallons per day per person.
Conservation could then bring the nexus of supply and needs even closer.
What are the barriers to getting it done? For starters the Metropolitan
Water District (MWD) will be less than thrilled and likely will put up as
many roadblocks as they can since the SDCWA is their largest customer. Okay,
once we get past that hurdle, what else? Is the technology available? Yes.
We have a full-scale plant the curious can visit in Las Vegas to prove that.
Money, of course. Where will the funding come from? Those that are smarter
than I am can figure that out, but for starters, raising the price paid by
water users will be important, especially the agri-business users who enjoy
cheap water rates.
We can do what Las Vegas did to do more with less, but it may take
collective spinal surgery at the water policy makers level, or do we simply
call that leadership. On the other hand, if the EPA denies a waiver for the
Pt. Loma Plant, the decision will already have been made for the water
policy makers and doers. Wouldn’t it be much better to be ahead of the power
curve and not behind it?