Tempe Town Lake will be in condition to be refilled starting today, though it will take a little more time for state regulators to sign off on the city's plans.
Crews have finished replacing the burst dam ahead of the original Oct. 8 estimate, and the city is confident the lake can be full by Nov. 1, Tempe Assistant City Manager Jeff Kulaga said while giving media tours of the project on Tuesday.
Three of the four rubber bladders are in place, have passed inspections and are ready to be inflated, Kulaga said.
Whereas the fourth dam will be placed in November, a temporary metal structure called a coffer dam will be completed today. The final section is ready to be shipped from Japan and should be in Tempe by late October.
Tempe is filling the lake before the final rubber section is here to accommodate the Ironman Triathlon in November. But much more is at stake for Tempe in restoring the lake.
"It competes with Sedona as the second-biggest tourist attraction to the state," Kulaga said.
Tempe will soon seek permission to fill the lake from the Arizona Department of Water Resources, which as been inspecting the dam replacement.
"That permission will be given fairly quickly once we get that request," said Mike Johnson, the department's assistant director and chief engineer.
Tempe isn't sure how fast the lake can be refilled because it hasn't determined how much water can flow at once down the Salt River. The water will come from Roosevelt Lake, where Tempe has rights to 13,500 acre-feet of water. The lake will require about 2,500 acre-feet, which translates to about 997 million gallons. The water will cost Tempe $50,000.
Some fish will flow into the lake, but Tempe will also stock the lake for anglers and import species that control the bug population by eating insect larvae.
The refilled lake will sit about one foot lower than before, as the 15-foot tall dams were made slightly smaller than the old ones so they can be filled with lower air pressure. They'll be kept at 4 pounds per inch, two pounds less than before.
The work went faster than expected because PCL Construction had crews on site 60 hours a week, PCL project manager Adam Gordon said. PCL will also install a pedestrian bridge over the dam, starting in November. The bridge will open in May and help protect the rubber structures by providing shade. A sprinkler system attached to the bridge will cool the bladders.
A study found heat and age caused one bladder to burst on July 20, an event that emptied the lake within hours. When Tempe installed the dams in 1999, it was told they'd last 30 years.
Bridgestone made the original dams and is supplying replacements at no charge. However, Bridgestone has stipulated that it will take the dams back in five years.
Tempe has explored other options for a structure that can be adjusted to allow the Salt River to flow over the structures. Once the lake is full, Tempe will ramp up its effort to identify a long-term solution, Kulaga said.
Also, Tempe is looking to recycle the old bladders, which are 240 feet long, 80,000 pounds and one inch thick.
"The stuff is so dense and so thick that you need some pretty powerful recycling machines," Kulaga said.