Hydrogeology And Simulation Of Groundwater Flow In Cedar Valley Utah County Utah

This CD contains a 125-page comprehensive study of the hydrogeology of Cedar Valley, Utah County, located in north-central Utah. The report includes 72 figures; two plates, one of which is a potentiometric map of the basin-fill, bedrock, and several perched aquifers; and seven appendices of data. Field investigations included groundwater chemistry sampling, regular water-level monitoring, and multiple-well aquifer testing. The field data were incorporated into a 3D digital groundwater flow model using MODFLOW2000. Seventy percent of the recharge to the Cedar Valley aquifer system is from precipitation in the Oquirrh Mountains. Groundwater generally flows from west to east and exits the aquifer system mostly as interbasin flow through bedrock to the northeast and southeast. The groundwater model showed a 39-year (1969-2007) average recharge to the Cedar Valley groundwater system of 25,600 acre-feet per year and discharge of 25,200 acre-feet per year. A significant volume of precipitation recharge (perhaps 4300 acre-feet per year) does not interact with the basin-fill aquifer but travels within bedrock to discharge to adjacent valleys or as bedrock well discharge. 125 pages + 2 plates

This 53-page report details aquifer parameter estimation in and near Cedar Valley, west of Utah Lake and the Lake Mountains, in Utah County, Utah. The UGS conducted five aquifer tests on the two most important aquifers in the study area-the principal basin-fill aquifer and the fractured-bedrock aquifer. The aquifer tests on bedrock wells are of particular interest because of the importance of the bedrock groundwater resource in the Cedar Pass area, where surface water and groundwater are scarce. The tests reveal valuable information about the interface between the basin-fill and bedrock aquifers, a key path for groundwater discharge from the Cedar Valley groundwater basin. Aquifer test analysis was combined with re-analysis of existing aquifer-test data and specific-capacity data from well logs to determine a range of hydraulic conductivity, transmissivity, and storativity for the aquifers. Anisotropy was identified in both the basin-fill and bedrock aquifers, and the bedrock aquifer was found to be bounded by semi-permeable aquifer boundaries; a wedge of Tertiary volcanic rock and buried faults are the likely barriers to groundwater flow near Cedar Pass.

This study is an investigation of the feasibility of an aquifer storage and recovery project using the existing water supply infrastructure of the city of Millville, Utah. The project involved injecting water from a public water supply spring into a public water supply well. Geochemical analysis indicates that the major ion chemistry of the spring water is very similar to that of the principal aquifer, however, the spring water would likely cause minor geochemical changes in the groundwater due to oxidation. The study also showed that the injection well had elevated nitrate concentration which is likely due to septic systems in the area. Overall, the pilot tests showed that injection of water for storage would not be detrimental to the principal aquifer, which has significant storage abilities beyond the capacity of Millville’s water system; however elevated nitrate in the aquifer is a problem that should be addressed.

The City of Millville, located in a prime location for aquifer storage and recovery (ASR), is having issues with elevated nitrate in the Glenridge well, a public water supply sourced from the Cache Valley principal aquifer. To alleviate high nitrate, the city performed an initial injection and pumping test using the Glenridge well. Millville injected water from Garr Spring, another public water supply source of which they own water rights, into the Glenridge well for one week at a rate of 500 gallons per minute. They then pumped the well while monitoring geochemistry to determine the effects on the Cache Valley principal aquifer system. The pre-injection nitrate concentration in the Glenridge well was 7.65 mg/l nitrate as nitrogen, and the nitrate concentration after pumping more than 172% of the volume of water injected was 6.52 mg/l nitrate as nitrogen. There is likely some dispersion of the injected spring water via advection in the aquifer.