Essentially, the facility would operate like an underground reservoir, and the city says it has its benefits. Permitting an underground storage facility isn’t as expensive as an above ground reservoir and capital costs are lower, according to city water officials. There are also fewer environmental impacts, and because the storage is underground the water supply doesn’t evaporate like it would aboveground.
The big challenge of underground facilities, such as the one Aurora and Castle Rock are looking into, called the Lost Creek Underground Storage Pilot Project, is engineering, said State Engineer Kevin Rein.
In the case of Lost Creek, there is already groundwater in the area. It’s in an “almost transient state,” Rein said. That means the water would eventually make its way to a river. Keeping stored water from also escaping to a river requires careful planning.
“It takes a lot of engineering and calculation,” Rein said.
But the project is completely doable, officials said. There is one underground storage facility that benefits the metro area, Centennial Water uses a system similar to what Aurora and Castle Rock are considering. That project serves Highland Ranch. For Denver, the city recharges aquifers. Rein said the rules that apply to those sites may look similar to the rules his agency is being charged with writing for underground storage facilities.
Aurora has ventured into similar storage projects before, but those facilities are used less for storage and more as a natural filter. The three underground facilities Aurora currently operates are part of the Prairie Waters project. Each is around 50-feet deep and as large as a football field.
Aurora City Council has approved an agreement to pay $50,000 to partially fund the Lost Creek Underground Storage Pilot Project, located northeast of the city in the Lost Creek basin. Castle Rock will pay $50,000 for the study too — which will survey the area, drilling bore holes to reaffirm the area is suitable for an underground storage facility.
The first phase of the Lost Creek project will look at data gathering. If all is successful in establishing a location for the facility, phase II will encompass feasibility, according to Alex Davis, Deputy Director for Water Resources in Aurora.
The feasibility side of project would address how obtainable the land is, what other data might be needed and who to collaborate on the project with.
This year the Colorado Legislature granted $200,000 for underground storage pilot studies. The joint effort between Aurora and Castle Rock is expected to cost $150,000, with the Colorado Water Conservation Board picking up a portion of the tab.
The pilot project’s first phase is expected to start this fall and take no longer than one year to complete. Aurora is working alongside Castle Rock, as the two have partnered on other water projects. Davis said the two have proven to be successful partners on water issues in the past, making this venture a no-brainer.
The 2016 State Water Plan identified 400,000 acre feet of water that needs storage by 2050. So it’s possible that underground storage facilities may become even more popular, Rein said.