Hydrogeologic characterization of the Fountain Formation: prospective aquifer storage and recovery targets in Front Range Colorado
Date
2018
Authors
Collazo, Daniel, author
Sutton, Sally, advisor
Sale, Thomas, committee member
Ronayne, Michael, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Aquifer storage and recovery (ASR) is a method of water storage that typically involves using the same well to inject water into and recover water from an aquifer. Benefits of ASR include lower capital costs than surface storage methods, negligible losses due to evaporation or potential contamination, and a much smaller land use footprint. This method of storing water is of interest for northern Colorado because of the location of existing water supply infrastructure and bedrock aquifers along the Front Range and the need for additional water storage. A potential storage zone for ASR in northern Colorado is the Fountain Formation. The Fountain is a Pennsylvanian-Permian arkosic conglomeratic sandstone with interbedded siltstone and shale that outcrops in a narrow, north-south trending belt from southern Wyoming to central Colorado. Within the outcrop belt, the Fountain is about 500 to 4500 feet thick and dips steeply to the east. The Fountain Formation was formed from sediments shed off the Ancestral Rocky Mountains, an uplift associated with the Ouachita-Marathon Orogeny, and deposited mainly in alluvial fans and braided streams. The composition of the formation is heterogeneous with permeable facies such as coarse sandstones adjacent to impermeable facies such as mudstones. This study characterizes the hydrogeology of the Fountain Formation to assess the feasibility of the Fountain as a storage zone for ASR, and in particular in northern Colorado. Data from 1262 wells in the Fountain were collected from the Colorado Division of Water Resources AquaMap database to characterize the hydraulic properties of the formation. The data were used to calculate specific capacity for each well and plotted on maps to help identify areas of interest for ASR. Within the formation there are wells with high yields and specific capacities which suggests that the Fountain can host high yield wells suitable for ASR. Water level elevation maps were also made for selected quadrangles and provide an approximation of the water level surface within the aquifer as well as the direction of water flow. Well-cemented outcrop samples were collected and tested for permeability using an air permeameter. The samples all have relatively low permeabilities, but it is likely that the less cemented lithologies have much higher permeabilities. The heterogenous lithology of the formation is likely able to store large volumes of water while preventing the water from migrating away from an ASR well. The results of this study suggest that the Fountain Formation is a feasible target for ASR implementation.