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Tempe tackles $2.5 million puddle that never dried up

High-algae nuisance water disrupts pH levels in Tempe Town Lake

 by Jonathan J. Cooper
 published on Monday, January 29, 2007

pH PHOBIA: The west side of Tempe Town Lake may not be as dry after Tempe builds a pipe to route Mesa water from the east side of the lake to the west side. Mesa dumps nearly 15 million gallons of reclaimed water into the Salt River daily which changes the pH levels in Tempe’s lake./issues/news/699459
Lee Kauftheil / THE STATE PRESS
pH PHOBIA: The west side of Tempe Town Lake may not be as dry after Tempe builds a pipe to route Mesa water from the east side of the lake to the west side. Mesa dumps nearly 15 million gallons of reclaimed water into the Salt River daily which changes the pH levels in Tempe’s lake.
 

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Heavy rain two years ago created a large puddle of water in the normally-dry Salt River bed east of Tempe Town Lake.

It never dried up.

The puddle is creating water quality problems in the lake, and Tempe officials are now spending $2.5 million to pump the excess water around Tempe Town Lake.

The high-algae nuisance water flows into Town Lake at the east end, forcing the lake's algae-treated water out from the west end, said Basil Boyd, a Tempe water resources hydrologist.

High algae raises water's pH level and makes it unsafe for swimming, Boyd said.

Officials treat Tempe Town Lake water to keep the pH level at or below the regulatory limit of 9.0, Boyd said.

But the constant water flow replaces some of the lake's treated water with the nuisance water's 9.6 pH level, Boyd said.

A pH above 9.0 can cause health problems, including eye irritation and bacterial infections.

"We treat for algae in the lake, but then more of it just flows in," he said.

High pH levels have affected two swimming events so far, Boyd said.

One was moved to a pool at ASU. The other was canceled.

Officials anticipated the bypass need when they constructed the lake's infrastructure but underestimated the amount of water that would need to be pumped, said Nancy Ryan, the project manager for Town Lake.

The construction project will enlarge a half-mile portion of an existing pipe, almost tripling the size to allow a pumping capacity of 15 to 20 million gallons per day.

The city will rent pumps to push the water into the pipeline, which will then be sent into a storm drain that empties into the Salt River bed west of the lake.

The problematic water initially collected near the lake after a heavy rain storm two years ago, Ryan said.

A high-ground water table kept the water at the surface. It is continually replenished by storm drainage upstream and reclaimed water from a Mesa treatment plant, Ryan said.

On Sunday, water discharges from the lake's west end ranged from about 105 to 194 gallons per second, according to data from the U.S. Geological Society. That's an average of about 216,000 gallons per day.

The bypass project is not part of an ongoing 90-acre habitat restoration project by the city and the U.S. Army Corps of Engineers, Ryan said. The project will add wildlife and vegetation between the lake's west dam and Priest Road.

"The presence of water will be helpful [to the restoration], but that's not why we're doing it," Ryan said.


Reach the reporter at: jonathan.cooper@asu.edu.



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