The village of Seven Springs, New Mexico, lies north of Fenton Lake in the valley of the Rio Cebolla in the Jemez Mountains of northern New Mexico. The valley is funnel shaped -- narrowest downstream -- with homes most densely packed at the bottom of the funnel. It is typical of many small communities scattered throughout the state in that residents rely on private wells for drinking water and on individual septic systems for disposal of household waste. The current population in the village and the valley is light -- about 50 permanent residents swelling to about 100 during the summer months. However, increased development of the valley is likely resulting in more permanent and seasonal residents. Ground water in the valley is shallow, ranging in depth from five to forty feet, and the threat to ground-water quality from increased development is high. To assess current and projected impacts to ground water from septic systems, water was sampled from wells at eleven homes, from two springs from which people obtain water, and from the Rio Cebolla above and below the village. Ground and surface waters were analyzed for major ions, metals, nutrients, volatile organic compounds, and coliforms. Coliform bacteria were found in Cebolla Spring, Hatchery Spring, and the Rio Cebolla. Water from Cebolla Spring tested positive for total coliform bacteria and water from the Hatchery Spring and the Rio Cebolla tested positive for both fecal and total coliforms. Residents who participated in the study were cautioned to avoid drinking water from the springs and the river. The ground water in the valley is of good quality with hardness under 37 mg/L (2.2 grains), total dissolved solids content less than 200 mg/L, nitrate at 0.2 mg/L or less and no coliforms or elevated metals. No detectable impact was found from the old gas station located in the village. There are some areas where anoxic conditions exist and at least one resident complained of rusty water with an odor of rotten-eggs. However, it was not determined if these conditions are the direct result of septic system discharge. Increased development may, however, adversely impact ground-water quality in the valley. Construction of a simple hydro geologic model shows that the septic discharge from only 46 homes with 127 year-round residents in the valley may be enough to increase nitrate levels in shallow ground water at the bottom of the valley to 5 mg/L -- half of the ground-water standard. Runoff from farming and grazing operations has likely contaminated the river and Fenton Lake with excessive nutrients. Additionally, an increase in population may bring more people into contact with spring and river water, which were been found to be contaminated with coliform bacteria.
ground water, surface water, field reconnaissance, epidemiological survey, conceptual hydrogeologic model, water sampling, septic system design
McDonald, William S.. "Urbanization of Seven Springs, New Mexico:An Evaluation of Current and Projected Impacts on Ground- and Surface-Water Resources." (2010). http://digitalrepository.unm.edu/wr_sp/131