Chandler joins SRP’s Roosevelt Dam project - SanTan Sun News SanTan Sun News

Chandler joins SRP’s Roosevelt Dam project

October 12th, 2022 SanTan Sun News
Chandler joins SRP’s Roosevelt Dam project
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By Ken Sain
Managing Editor

Water is such a precious resource that some Valley cities, including Chandler, are paying tens of thousands of dollars just for the possibility of increasing their supply for a limited time.

Chandler City Council voted to pay more than $61,000 to be part of a Salt River Project study that wants to increase water supply after a flood from 20 to 120 days. By paying to be part of the study, the city would get about 5% of that water – if the plan is approved by the United States Bureau of Reclamation and the Army Corps of Engineers.

I think it’s great idea,” Councilman Matt Orlando said at the Sept. 22 meeting. “Of course, it gets water flowing as well, and obviously we’re all concerned about water.”

The project focuses on Roosevelt Dam, which is the oldest dam built as part of the federal reclamation program. The dam was renovated in the 1990s and is now 357 feet tall. However, the water level of Roosevelt Lake is only allowed to reach 290 feet, leaving space for major flood events.

In the case of a major flood event that rises the level of the lake past 290 feet, Salt River Project has 20 days to release enough water to lower the level back to its goal height. SRP is hoping to get permission to extend that time to 120 days, allowing it to release water more slowly so its partner communities can store it for their own use.

We’ve been looking at how we can maintain safety while improving our ability to manage water supplies, what we identified was just an incremental change in these operations in the first five feet of that 24 vertical feet of flood control space,” said Ron Klawitter, the senior principal for water systems projects at SRP.

Klawitter said there are two zones left free above the water level for safety, because water flowing over the dam is the worst-case scenario. The first immediately above the water level is a 24-foot level for flood control. That can handle most 100-to-200-year flood events.

Klawitter said that the 45 feet above that could safely handle a 2,000-year flood event, though he also said there’s not enough water flowing down the Salt River to fill Roosevelt Lake that high.

Under the proposed change SRP is asking approval for, the utility would still open the dam’s flood gates and allow most of the excess flood water to travel downriver in the first 20 days. However, once it was five feet above the goal, SRP would slow the flow and have the extra 100 days for cities like Chandler to get a share of that water to store or use however they see fit.

The study costs $1,211,549 and there are 14 entities joining SRP to be part of it. The cost to Chandler is $61,347. The partners met to work out how much water they would get and then paid the same percentage of the cost.

Klawitter said the percentage depended on how much water each entity could handle in those short time spans. Chandler agreed to 5.06%. Smaller cities, such as Avondale (7.83%), could take more and will pay more for the study.

What SRP is asking for seems quite small compared to the $1.2 million price tag for the study. Klawitter said a lot of expertise went into coming up with the plan.

The main cost drivers are the risk assessment,” Klawitter said. “So it was a whole team of engineers that spent about a year evaluating the proposal. This is just really understanding that the impact if a safety issue existed.

The Phoenix metropolitan area has over five million people living downstream of this dam. So we worked with the Bureau of Reclamation and the partners had to fund a team of reclamation engineers to do a very, very specific risk assessment of this proposal,” he continued, adding:

“They looked at what happens if an earthquake occurs. Well the dam has more water in it to conclude that there is no increase in risk. They did flood-routing analysis to make sure that we could properly pass the flood downstream. So there was a lot of care and careful technical eyes on this proposal to ensure that all citizens downstream and all resources downstream would maintain safety.”