New Mexico Geological Society Annual Spring Meeting — Abstracts

Slug tests were performed on 11 nested piezometer sites completed in the upper Santa Fe Group in the Albuquerque area to estimate hydraulic conductivity of the regional basin-fill aquifer system near Albuquerque, New Mexico (Thomas and Thorn, 2000). Geologic mapping, cuttings analysis, and borehole geophysics for these and neighboring production wells were used to differentiate subsurface facies and textural trends in the Albuquerque area. The Sierra Ladrones Formation contains axial-fluvial deposits of the ancestral Rio Grande and basin-margin deposits derived from the Sandia and Manzano Mountains. The Arroyo Ojito Formation contains deposits of the ancestral Rio Jemez/Guadalupe, Rio Puerco, and Rio San Jose fluvial systems, which drained the western border of the basin.

Three major textural intervals or zones are recognized within fluvial lithofacies of both formations: 1) a lower muddy sand; 2) a middle sand, mud and gravel; and 3) an upper gravel and sand. The lower fine-grained zone is a confined unit commonly encountered near the base of wells west of the Rio Grande. Middle and upper zones tend to thicken eastward from ~75 m along the Ceja del Rio Puerco to >270 m beneath northeast Albuquerque. The middle interval is typically dominated by upward-fining sequences of sand and sandy mud that coarsen and grade upward into the overlying interval.

Of the 25 piezometers tested, half were screened within the middle sand, gravel and mud facies. This interval tends to have the highest hydraulic conductivity values, ranging from 3.3x10^-2 cm/s (92 ft/day) in northeast Albuquerque to 6.7x10^-4 cm/s (2ft/day) near downtown. In general, hydraulic conductivity increases to the north and the east within the middle interval. The upper interval is an unconfined unit with hydraulic conductivity (n=4) ranging from 2.4x10^-2 cm/s (68 ft/day) to 406x10^-3 cm/s (13 ft/day). Wells with piezometers in the lower interval (n=8) have hydraulic conductivities ranging from 9.5x10^-3cm/s (27 ft/day) to 5.3x10^-5cm/s (<1 ft/day).