Terry Ranch Aquifer Storage Facts

Terry Ranch groundwater is not connected to the groundwater in and around Greeley. Terry Ranch groundwater comes from deep aquifers (200 to 1,200 feet underground) and classified by the state as being non-tributary. Non-tributary groundwater is isolated from surface streams and reservoirs, and it can be reused many times. Most groundwater use in and around Greeley is from shallow alluvial wells pumping tributary groundwater. Tributary groundwater pumping typically requires the user to replace the amount pumped back to the river.

Several communities in the West use aquifer storage and recovery to provide their communities water. It is a common practice, even in Colorado. 

 List of Water providers in Colorado using groundwater 

No, groundwater is not affected by droughts or disruptions to watershed.  This is why Terry Ranch groundwater could be very valuable when operated with the city’s existing surface water system.  The city will use Terry Ranch primarily as a drought supply or when there are disruptions to our existing surface water system.  The Summer 2020 fires in the Poudre watershed were a good example of this type of threat.  Greeley will continue to rely mostly on its surface supply, turning on Terry Ranch only when needed.

Greeley has thoroughly investigated potential sources of surface contamination that could hurt the quality of the Terry Ranch groundwater.  The city evaluated surface uses in the aquifer recharge area west of the ranch.  The city specifically looked at Fort Collins’ application of biosolids (residue from the wastewater treatment) at Meadow Spring Ranch.  Results of these studies found that it would take over 1,000 years for solids applied at Meadow Spring Ranch to reach the Terry Ranch groundwater.  Over that time, most compounds in biosolids will degrade.

There are no operating oil and gas wells on Terry Ranch.  The city investigated the potential for future energy development on the ranch.  Based on all available evidence, it appears the risk for future oil and gas development on the ranch is low.  Greeley cannot conclusively rule out  future oil and gas development, but in that event the city would use one of many legal and permitting mechanisms to protect groundwater during drilling.  Any oil and gas deposits will be thousands of feet below the Terry Ranch groundwater.

Greeley also evaluated the potential for Trichloroethylene (TCE) contamination from military facilities in Wyoming. The source of contamination is approximately 14 miles northwest of Terry Ranch property boundary, and the leading edge of the contaminated groundwater is 4.5 miles northwest of the Terry Ranch boundary. Neither the source of contamination nor the location of the TCE plume are in the recharge area of Terry Ranch, and the contaminate groundwater is not traveling in the direction of the Terry Ranch wells. The TCE leaked into the White River formation, which is separate from the Upper Laramie Aquifer, the source of the Terry Ranch water.  The TCE leakage is well understood and is being mitigated by the U.S. Army Corps of Engineers. 

While we cannot say there is no risk, it is a very low risk.  Compared to other groundwater sources, like the Denver Basin that serves many communities with groundwater in Metro Denver and underlies many industrial operations, Terry Ranch has very little surface development and has a very low probability of ever being developed.

The aquifer underlying Terry Ranch is not completely full.  There are empty regions than can accommodate injected water.  Groundwater modeling confirms that the aquifer can accommodate the volumes of water Greeley anticipates injecting/storing.

If the purchase agreement is approved, Greeley will own rights to both the groundwater and the underground aquifer where water will be stored.  In other words, the purchase gives Greeley all legal rights necessary to store water at Terry Ranch.  Before injecting water underground, Greeley would need to receive a water quality permit from the EPA and a permit from the State of Colorado certifying that Greeley will follow state guidelines on water accounting, well construction, etc. Such permits are fairly routine; in fact, Greeley already received similar authorizations to perform a pilot injection test this fall.