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Friday, May 24, 2013
Covering Dallas, Monmouth, Independence, Falls City and surrounding areas since 1868
Public Works Director Fred Braun explains how Dallas' Aquifer Storage and Recovery project works at the city's water treatment plant on Monday.
March 19, 2013
DALLAS -- Facing increasing water demand, in 2006 the city of Dallas launched a project to find a way to collect and store more fresh water for use during dry months. Ironically, the city found it in an aquifer brimming with salt water.
Now that project and more like it will save the city millions -- at least temporarily -- in costs to increase water supply or capacity.
The "Aquifer Storage and Recovery" (ASR) project allows for treated drinking water to be pumped into the well in the rainy months -- between 45 and 50 million gallons each winter -- pushing the salt water deeper into the aquifer and creating a bubble of fresh water.
In the summer, when supply is down and demand the greatest, the city draws that water back out, retreats it and sends it to customers.
One of only a fewsuch wells in the state -- Dallas Engineering and Environmental Services Director Fred Braun is only aware of others in Salem, Beaverton and Tualatin -- the city's ASR is closely monitored for water quality and impact on surrounding wells.
Aquifer Storage and Recovery systerm that is used by the city of Dallas which pumps fresh water underground until it is needed and then can be pumped back to the surface when needed.
So far, the results have been encouraging.
"We are successfully testing it," said Braun. "It's showing that the aquifer performance is getting better and better over time. The water quality is getting better. It is very successful and it bodes well for the future water supply for the city of Dallas and keeping the rates low for our ratepayers."
ASRs keep water rates down because they are relatively inexpensive -- costing between $500,000 and $750,000 to install and about $10,000 annually to maintain, including costs for equipment replacement.
Braun also noted functioning ASRs are an insurance policy, giving the city a secondary source of water if Mercer Reservoir, Dallas' main water source, were to be contaminated.
Currently, the city can draw about 15 million gallons out of the ASR when needed, mostly in August and September. Water can be pumped out of the well at a rate of 333,000 gallons per day to supplement regular water supplies that can reach peak demand of about 3 million gallons per day in August, but average between 1.5 million and 1.8 million gallons per day.
Possibly the most important benefit to the city -- and its ratepayers in this budget-conscious time -- is the ASR concept could push a major water supply project two decades into the future.
As noted in the ASR annual report released Feb. 15, water quality and well performance is improving each year. Braun said the project has been going so well, a follow-up feasibility study conducted in 2010 recommended installing two more ASRs.
Braun said those are slated for 2017 and 2022.
Without those plans, the city could be looking at having to build another dam on Rickreall Creek or pipe and treat water from the Willamette River as soon as 2020.
Building a new dam comes with a price tag of about $25 million and would raise water rates to customers about 50 percent to pay for the new infrastructure.
"We can store a great amount of water underground without having to build something more," Braun said. "The burden of additional supply would have to be borne on the backs of existing ratepayers. The nice thing about an ASR is that we can build these with just the systems development charges we charge for new development."
Braun said, beyond the cost, a new dam would have to comply with tightening environmental standards, which make such projects difficult to approve.
Drawing water from the Willamette? That comes with its own set of challenges.
"That is another very costly alternative, as well as getting by the perception in the public that they don't want to drink Willamette water," Braun said.
However, Braun said ASRs are only a medium-term water solution. The city also is looking to conservation and using treated wastewater for irrigation as methods to further delay the need for a major expansion project.
"We are looking at those a lot harder than a brand new dam or the Willamette option," he said.
At least for the next 20 or more years.
"It would be a question that would be asked during the whole feasibility study for a new dam. They would ask `Have you looked at the other options before you consider a dam?'" Braun said. "So this is the option we are looking at for now."
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