ESTIMATES OF THE HYDRAULIC PARAMETERS OF AQUIFERS IN CACHE VALLEY, UTAH AND IDAHO

Hydraulic parameters of aquifers in Cache Valley were compiled from existing but largely unpublished data, from specific capacity data reported in well drillers' records, and from aquifer tests conducted for this study. A GIS database was also created to organize this information.

A complete and thorough literature review was performed, which included obtaining unpublished aquifer test data from state and federal agencies, as well as reviewing Drinking Water Source Protection plans for each municipality in the valley.

Well drillers' records were obtained from the Utah Division of Water Rights website and examined for pertinent information. Screened unit intervals from 1,314 well drillers’ logs were databased and mapped. Transmissivity was estimated from specific capacity values obtained from 378 well drillers’ records and keyed into a spatial database. Five pumping tests were also performed. Four of the tests were single-well tests using private domestic wells, and one was a multiple-well test using high-yield municipal wells owned and operated by Logan City. The sites selected for conducting the aquifer tests were: the Stevenson well in Weston, Idaho in an unconfined alluvial aquifer; the Tomkinson well south of Newton, Utah in the confined gravels of western Cache Valley; the Henningsen well east of Paradise, Utah in the Salt Lake Formation; the Luthy well east of Cove, Utah in the Salt Lake Formation; and three Logan City, Utah wells in the principal aquifer. Drawdown data collected for each test provide clues regarding the surrounding geology, including the existence of a low permeability barrier and the possible presence of fractured material. The transmissivity and storativity of the principal aquifer, into which the Logan City wells are screened, have been estimated to be 300,000 square feet per day (ft2/day) and 0.000275, respectively. Drawdown curves from wells penetrating close to the East Cache fault display boundary effects.

The GIS database shows that the principal aquifer underlies the east side of the valley between Smithfield and Hyrum, and has the highest density of wells, most of which are screened into confined unconsolidated gravels. The transmissivity is highest in the principal aquifer and decreases to the west, north and south of it.