New Mexico Geological Society Annual Spring Meeting — Abstracts

Uranium has been tested in domestic water wells in the Arroyo Hondo, Des Montes, Arroyo Seco and El Salto neighborhoods of central Taos County. Analyses funded by the Taos Soil and Water Conservation District have found spots south of the Rio Hondo that approach or exceed EPA drinking standards of .030 mg/L.

  Uranium occurrences are in alluvial fan clastic facies extending from the Sangre de Cristo Mountain westward for 10 miles to the Rio Grande Gorge. The uranium source rock is probably the mid-Tertiary granitic plutons or late-stage rhyolitic dikes in the mountain headwaters that eroded into the Tertiary-Quaternary alluvial fan complex.

  Varying water levels over time may have allowed the phreatic oxidized zone to develop uranium in a soluble form that is carried downward to the reducing aquifer environment similar to commercial uranium deposits elsewhere. The process is complicated by local wells of heavy drawdown, periods of drought, a fractured underlying dacite volcano, fault zones, acequia recharge, gaining and losing stretches of the adjacent Rio Hondo, mountain-front undercharge, or other factors.

  Health effects of higher uranium concentration may be remediated depending on concentration and required treatment scale by various methods. These methods can be as simple as filters for tap water for domestic use to larger reverse osmosis treatments or ion exchange systems for community mutual domestic wells.