Scottsdale growth means more thirsty people

North Scottsdale prides itself on preservation of the Sonoran Desert, but even so, the residential and commercial growth officials expect to happen there over the next 10 years will require plenty of water.

GRAPHIC: See the water plant's location

So much so that the city intends to spend about $90 million to expand its northern water plant’s capacity by 60 percent to treat drinking water as part of a plan to help meet the city’s growing thirst through 2017.

Construction is already under way on a new reservoir at the Central Arizona Project Water Treatment Plant, 8660 E. Union Hills Drive, and work could begin on a third treatment facility on the site by the end of the year, said Art Nuñez, treatment plant director. The additions will raise the plant’s capacity to turn Colorado River water into drinking water from 50 million gallons per day to 80 million. The project could take up to two years to complete.

“That 30 million gallons is not necessary tomorrow. But within a few years we will need that full capacity,” Nuñez said.

The CAP treatment plant serves the city north of Indian Bend Road. The latest growth figures for that area show an increase of more than 81,800 residents and more than 25 million square feet of nonresidential development between 2003 and 2020, said Harry Higgins, a long-range planner for Scottsdale.

In the coming weeks, Scottsdale’s Development Review Board is expected to review design plans for the new treatment plant, submitted last month.

“We’re basically far enough along that we know what we need and we need to start working with the manufacturer,” Nuñez said.

Dave Mansfield, the city’s water resources general manager, said the new facility will be the third one on the site, but the first to use a high pressure membrane filtration system that only needs about a quarter of the space each of the older plants on the site occupies.

“That’s the best available technology to ensure high water-quality treatment,” he said. “The footprint is dramatically less.”

While the existing facilities require about 15 acres each for such things as ponds, the new plant only needs three or four acres, Mansfield said.

“You need large concrete tanks. It’s the way people have done it for years,” he said of the existing plants.

Nuñez said residents’ demand for water already reaches the capacity of the existing plants on a regular basis during peak times in the summer. The city stores finished water in two existing five-million-gallon reservoirs for such instances. Workers are already in the midst of building a third, six-million-gallon reservoir.

“In the morning when everybody’s getting up and getting ready for work, we see a higher demand. Then it’ll start picking up again in the evening,” he said.

The additional 30 million gallons per day the new plant will treat will come exclusively from the Colorado River, Nuñez said.

“It’s better and less expensive to treat surface water than accessing the large wells and depleting the aquifer,” he said, referring to the city’s underground water table.

Last year, Scottsdale achieved what’s called “safe yield,” when the amount it removes from underground wells equals the amount the city puts back in, he said.

“Basically, for the first time in our history, we put as much water into the aquifer as we pulled out in 2006. That’s a major accomplishment,” Nuñez said. “That allows us to assure our residents and regulatory agencies that we’re not depleting our resources. We’re using them wisely.”

Only a small portion of the expansion will be built on land the city is trying to acquire through eminent domain, Nuñez said. The city is trying to condemn the land from Hualapai LLC, a private investment group which in 2005 outbid the city and purchased 7 acres at a state auction.

Scottsdale was using the land because it had signed a 10-year lease with the State Land Department, but is now saying the lease is not valid. Hualapai is opposing the condemnation and claims the city owes them close to $10 million, or the value of the lease. A trial has been scheduled for next year.

Nevertheless, construction on a large $59.4 million building to house a granulated carbon filtration system on the disputed land is moving along. That project, which is separate from the $90 million treatment plant expansion, is meant to meet federal mandates to remove byproducts from the treatment process. The filter also has the side benefit of making drinking water taste better, officials have said.

By the numbers

Growth north of Indian Bend Road between 2003 and 2020:

• More than 81,000 new residents

• More than 25 million square feet of nonresidential development

Source: Scottsdale