On a hot, dusty plain northeast of Denver, utility contractors on Monday drilled a super-deep borehole, looking for the geologic equivalent of a bank vault where the city could stash water for dry times.
“Drought is coming,” Denver Water officials declared, moving ahead on a $1.36 million investigation.
If the density of shale rock 1,900 feet down proves promising, dozens more wells would be drilled around metro Denver, where saved water would be injected and, hopefully, drawn back when needed.
The bowl-shaped aquifers beneath Denver cover an area the size of Connecticut.
“We need to figure out how many wells it would take to get an acre-foot of water in there,” said Denver Water engineer Bob Peters who oversaw the drilling. “It might take us many, many wells.”
Denver is taking these first steps amid drought, with California and other Western states facing severe shortages, and steady Western population and economic growth that raises water concerns.
A Colorado Water Plan, which is to be unveiled in December, extols “aquifer storage and recovery” as part of a strategy for securing supplies. State planners estimate there’s enough space in bedrock to store 150 million acre-feet of water — 12 times the entire annual flow in the Colorado River.
Pumping excess treated water underground during wet years has emerged as a cost-effective option compared with building surface reservoirs. Aquifer storage has benefits, including no evaporation. High plains and mountain ecosystems wouldn’t be disrupted with dams.
Phoenix, San Antonio and Wichita are turning to underground storage, said Cortney Brand, vice president for Leonard Rice Engineers, which is working with Denver Water.
Setting up aquifer systems would take years — and depend on having excess water to inject.
“As we face future challenges, such as population growth and climate change, we will need additional storage to deal with increasing risks to our ability to meet the needs of our customers while providing flexibility, redundancy and resiliency in our system,” Denver Water manager Jim Lochhead said.
“Studying the feasibility of storing water underground is part of Denver Water’s ‘all of the above’ strategy, which includes conservation, expanding sources of supply and recycling water,” Lochhead said.
On Monday, Fort Lupton-based Hydro Resources drillers cut an 8-inch-diameter borehole, 20 feet an hour, using a three-prong steel bit, churning through sandstone, silt, clay and shale rock. They saved sediment samples for analysis.
Drillers bored two wells this month along Interstate 70, and the well drilled Monday was the third of four for this project.
If all goes as planned, Denver Water officials said, they could begin work seeking government permits next year. Water stored underground would be treated again, they said, before delivery to more than 1.3 million residents.
The work creating aquifer storage would entail placing steel pipe casing, about 1 foot in diameter, for injecting and withdrawing water. Challenges include difficulty controlling injected water, retrieving it and installation of pipelines to reach people.
Bruce Finley: 303-954-1700, bfinley@denverpost.com or @finleybruce
