Geohydrologic data from twenty-four test holes drilled in the Piceance Basin, Rio Blanco County, Colorado, 1975-76

Abstract

Twenty-four test holes were drilled in the Piceance basin, northwestern Colorado, to obtain geohydrologic data from the Uinta and Green River Formations of Eocene age. Depths of test holes ranged from 640 to 2,800 feet. The maximum quantity of water discharged during the air drilling of individual test holes ranged from 14 to 880 gallons per minute. The specific conductance of water discharged during drilling ranged from 100 to 50,000 micromhos per centimeter at 25 degrees Celsius. Aquifer tests made during drilling indicate transmissivity at four sites ranged from 100 to 1,600 feet squared per day and the storage coefficient at two sites ranged from 0.0004 to 0.00016. Depths to the static water level ranged from 30 to 695 feet. Water levels were measured in each test well, and potentiometric maps constructed from these measurements are comparable in configuration and altitude to those previously drawn from composite-head data. Water samples taken during drilling indicate that, except for water from the Uinta Formation, the water in Piceance basin is generally not suited for domestic water supply due to the presence of excessive amounts of certain trace constituents, notably fluoride. The average concentration of dissolved solids, based on data from the test holes, was 909 milligrams per liter (mg/L) for the Uinta Formation, 828 mg/L for the upper part of the Parachute Creek Member of the Green River Formation, and 3,460 mg/L for the lower part of the Parachute Creek Member. (Woodard-USGS)