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Tucson Narrows CAP Options
- The City of Tucson has narrowed its options
for using its Central Arizona Project water allocation to four: direct
treatment and delivery through the existing treatment plant after
replacing deteriorating mains; augmenting treatment with a filtration
stage to remove salts; blending CAP water with equal amounts of groundwater;
and recharging CAP water using spreading basins, streambeds, and/or
injection wells.
- An ongoing study by Dames & Moore considered a number of options,
several of which have been set aside. Options no longer being considered
include: rejecting the CAP water and continuing to pump groundwater;
exchanging CAP water for Pinal County groundwater; exchanging CAP
water for groundwater currently pumped by local copper mines; and
trading Tucson's CAP water to entities in other states. The final
plan is expected to be some combination of the four options still
under study.
- In addition, efforts are being made to exchange CAP water with
area farmers. Tucson officials have negotiated with Farmers' Investment
Co. about exchanging up to 20,000 acre-feet of CAP water per year
with pecan growers in the Sahuarita and Continental areas for credits
to pump groundwater. No small obstacle to the plan would be the cost
of building a pipeline--estimated at $5 million to $10 million--from
the CAP aqueduct to the agricultural lands.
- The final Tucson CAP plan, scheduled for adoption later this year,
likely will take five years to fully implement. In the meantime, Tucson
is looking at various short-term strategies to make use of CAP water
and alleviate a potential summer peak demand problem. Options such
as pouring CAP water into washes to recharge on the nearby Tohono
O'odham reservation and running CAP water through the City's effluent
distribution system to facilitate streambed recharge have been raised.
Each faces substantial logistical and legal hurdles.
- The Dames and Moore report indicates a tradeoff between keeping
water rates as low as possible and minimizing impacts of lower quality
water on households. As the bar chart shows, the City's original strategy
of chemically treating and directly delivering CAP water would cost
a typical household in the year 2000 only $81 a year in increased
water bills.
- Unfortunately, experience and further research showed that the
saltier, more corrosive water was costing households considerably
more in the form of failing pipes, damaged landscaping, and shortened
useful life for water-using appliances. Such household costs were
estimated at $132 a year.
- By contrast, enhanced treatment including filtration to remove
dissolved solids imposes the greatest rate increase, $116 a year in
the year 2000. However, there are no additional household costs associated
with this option.
- Household water bills would go up about $115 a year if CAP water
and groundwater are blended in equal amounts before delivery to customers.
Using blended water would increase household costs by $70 a year.
- If all CAP water is recharged, household water bills in the year
2000 would increase between $106 to $114 a year. The final cost would
depend upon the recharge method and location. Recharge likely would
increase household costs about $19 a year.
- According to the report the recharge option could present problems
because under new state rules Tucson may be unable to demonstrate
an assured water supply for new development.
- Tucsonans are likely to resist any proposed water rate increases
for CAP water. A survey found that most residents "may be unwilling
to pay even small rate increases" for CAP water because it is harder
and saltier than groundwater. The status quo is, indeed, appealing,
with an anticipated increase in the year 2000 of only $48 a year if
the city remains on groundwater.
- Public meetings are to be conducted during June to gather input
on the various options. A final report is scheduled to go to the City
Council June 26.
- Meanwhile, an effort is underway to place an initiative on the
November ballot specifying how CAP water is to be used. It is a case
of déj++ vu all over again, with many of the same people spearheading
the initiative effort who backed an all-recharge initiative in 1987
to commit the city to recharge its entire CAP allocation. That initiative
failed.
- Since then, a lot of CAP water has gone under the bridge and into
people's homes, with destructive and costly results. Supporters of
the new initiative now feel they have a better chance to succeed with
a CAP initiative. Various strategies are proposed for using CAP water
including dumping the water into area washes and rivers, building
recharge ponds and installing injection wells in the city's central
well field. Part of the proposed plan also includes selling CAP water
for mining and agricultural use.
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