City says Tempe Town Lake dam was working properly until break

TEMPE, AZ - An investigation into what caused a break at the Tempe Town Lake dam has revealed the rubberized dam was working properly up until the minute it failed.

The City of Tempe said in a news release Monday that pressure records show everything was normal in the minutes leading up to the break.

Then at 9:44 p.m. last Tuesday, 'bladder 2' failed, sending one billion gallons of water out of the urban lake and down the Salt River channel through Phoenix and beyond.

The city said there is no indication of a precursor of the event or a gradual decline.

Although released surveillance video shows water pouring over the dam and then a bright flash of light occurring minutes before the collapse, the city said there was no indication of a control system failure either, such as overfilling or excessive pressure build up.

Tempe officials said they ruled out foul play after they said a tear developed in the rubberized dam.

The ABC15 Investigators have also obtained the most recent inspection report of the dam done by the City of Tempe’s Water Utilities Division on May 28, 2010.

It includes comments about an “air leak under the midpoint of #2 bladder,” a “bulge present under No. 2 bladder,” and a “small piece of glass in No. 2 bladder at bottom.”

City officials tell ABC15 all of these items were on the bottom of the bladder near the foundation, not further up where the rupture reportedly occurred.

According to the city, rubber dam manufacturer Bridgestone visited the dams after the air leak and bulge first appeared in mid-2008 and asked that the city monitor the pressure records.

The city blames the dam's manufacturer, Bridgestone for the break, while the company says the dams were sold with a 10-year warranty that expired in 2009.

The City of Tempe said Bridgestone is paying for the replacement work.

The man-made lake, equipped with four dams on its west end, is nearly empty now.

Tempe Mayor Hugh Hallman said the lake would probably not be reopened until sometime this fall.