Hydraulic and water-quality indicators of aquifer zones contributing groundwater flow to wells in the Santa Fe Group aquifer system near southeast Albuquerque, New Mexico, 2013–16

Abstract

An ethylene dibromide (EDB) plume extends approximately 5,880 feet northeast from the Bulk Fuels Facility on Kirtland Air Force Base. The leading edge of the EDB plume is about 3,700 feet upgradient from several water-supply wells. The water-supply wells are screened in the upper Santa Fe Group aquifer system. Within the upper Santa Fe Group, two primary clay-rich layers, the A1 and A2 units, separate water-producing zones. The U.S. Geological Survey, in cooperation with the Albuquerque Bernalillo County Water Utility Authority and the U.S. Air Force, installed four sentinel well nests and two aquifer-test pumping wells between the EDB plume and the water-supply wells. The purpose of the sentinel wells is to provide early warning of EDB plume migration towards water-supply wells. The sentinel well nests include at least three wells that are screened above, in between, and below the A1 and A2 units. The two aquifer-test pumping wells, installed for performing hydraulic tests on the aquifer system, are screened across both clay layers, as are the nearby water-supply wells. Well-bore flow logging indicated that greater than 60 percent of groundwater flow to the wells was through the deepest interval below the lowermost clay layer (A1 unit). The interval between the A1 and A2 units is the second most productive interval. Water-quality data also indicated that water drawn from the aquifer-test pumping wells and previously studied nearby water-supply wells is most similar in composition to water from the sentinel wells screened in the middle and deep intervals. Introduction The Albuquerque Bernalillo County Water Utility Authority (Water Authority), Kirtland Air Force Base (KAFB), and the Veteran’s Administration (VA) hospital complex operate production wells located in and near southeast Albuquerque, New Mexico, that supply drinking water to the Water Authority distribution system, KAFB facilities, and VA facilities, respectively (Air Force Civil Engineer Center, 2013; fig. 1A). Leaks in an underground pipe used to transfer aviation fuels at the KAFB Bulk Fuels Facility (BFF) were discovered in 1999 during pipeline pressure testing (U.S. Air Force, 2011). While it is not clear when the pipeline began leaking aviation fuel, the BFF (fig. 1B) area has been in use for fueling operations since the 1950s (U.S. Air Force, 2011). After migrating through the unsaturated zone and to the water table, the fuels formed an ethylene dibromide (EDB) plume composed of components of leaded aviation fuel within the groundwater. Prior to widespread development of groundwater resources in southeastern Albuquerque, groundwater near the present-day location of the BFF flowed to the southwest. In about 1980, however, groundwater began flowing to the northeast towards a large area of potentiometric surface decline caused by groundwater pumping from water-supply wells (Falk and others, 2011; Powell and McKean, 2014; Rice and others, 2014; fig. 1A). The most laterally extensive fuel component, EDB, has moved parallel to the mapped groundwater flow direction and has formed a plume that, as of December 2016, extended about 5,880 feet (ft) northeast from the BFF area (U.S. Army Corps of Engineers [USACE], 2017). The leading edge of the EDB plume (defined as the 0.05 microgram per liter [μg/L] concentration contour) is about 3,700 ft away from the nearest downgradient water-supply well (RC-5, fig. 1B) operated by the Water Authority. In December 2015, detectable concentrations of EDB (method detection limit 0.019 μg/L) extended below the water table at depths ranging from 65 to 85 ft within the EDB plume (USACE, 2016). Hydraulic and Water-Quality Indicators of Aquifer Zones Contributing Groundwater Flow to Wells in the Santa Fe Group Aquifer System near Southeast Albuquerque, New Mexico, 2013–16 By Rebecca E. Travis and Nathan C. Myers 2 Hydraulic and Water-Quality Indicators of Aquifer Zones Contributing Groundwater Flow to Wells in the Santa Fe Group