HYDROGEOLOGIC, STRATIGRAPHIC, AND STRUCTURAL IMPLICATIONS OF DRILLING DATA COLLECTED FROM TWO DEEP (2500 AND 3000 FEET) MUNICIPAL SUPPLY WELLS IN THE ALBUQUERQUE BASIN, RIO RANCHO, NEW MEXICO

Subsurface data (lithologic and geophysical logs) collected from two deep municipal supply wells are combined with data from long-term (7-day) pumping tests, remote sensing data (aeromagnetic surveys), geologic mapping, and geochemistry data to determine variations in subsurface stratigraphy, chemistry, and aquifer characteristics in a portion of the Albuquerque Basin. City of Rio Rancho Well 10A, is completed to a depth of 2500 ft in the Santa Fe Group, approximately 1.5 mi west-southwest of City Well 22, completed to a depth of 2990 ft in the Santa Fe Group aquifer. Lithologic and geophysical logs indicate a thickening of deeper lithologic units in Well 22 relative to Well 10A. Seven day constant-rate pumping tests conducted in both wells encountered a limiting boundary. Calculations of radial distance to the boundary for both wells correspond to a fault located between the wells that has been mapped at the surface and identified in aeromagnetic surveys of the Albuquerque Basin. Geochemical data suggest that the structure may act as a geochemical divide, with groundwater samples collected east of the fault being geochemically distinct from samples collected to the west. Two clay beds identified and correlated between the two wells may act as a confining unit, limiting the vertical connection between deeper sediments and the shallower aquifer. Variations in water chemistry above and below the clays are inferred from geophysical logs and comparison to nearby wells completed entirely above the clay beds.