HR: 0830h
AN: H41F-1051    [PDF]
TI: Septic Nitrate Contamination of Multiple Municipal Wells: Trends and Remedial Efforts
AU: Dragan, D
EM: ddragan@mail.co.washoe.nv.us
AF: Washoe County Department of Water Resources, 4930 Energy Way, Reno, NV 89502 United States
AU: * Kropf, C A
EM: ckropf@mail.co.washoe.nv.us
AF: Washoe County Department of Water Resources, 4930 Energy Way, Reno, NV 89502 United States
AB: Fifteen years of groundwater quality monitoring in the Spanish Springs Valley, Nevada, have shown increasing levels of nitrate in municipal wells. Three of the six municipal wells have nitrate concentrations just under the U.S. EPA MCL of 10 mg/L. More than 2,000 homes on septic sewage disposal systems are located within a four square-mile area - with almost half of these systems within 2,000 feet of one or more of the municipal wells. A 1999 USGS study concluded that increasing nitrate levels can be linked to local septic systems. This study, completed in January 2003, is a preliminary step to define the lateral and vertical extent of nitrate contamination in the valley and identify the vertical mixing zone of the pollutant. The preliminary conceptual model of contaminant migration was confirmed by the study. Although a discontinuous clay aquitard is acting to slow vertical migration of contamination, the combination of numerous septic systems and their proximity to shallow-screened, high-volume municipal wells, leads to the present situation. Concentrations of nitrate in groundwater collected from all existing shallow monitor wells were above the MCL, with a maximum concentration greater than three times the MCL. In addition, concentrations of nitrate in groundwater collected from deeper wells within the assumed plume were elevated as compared to background concentrations.
DE: 1803 Anthropogenic effects
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1884 Water supply
SC: Hydrology [H]
MN: 2003 Fall Meeting