Residential water supplies in the community of Fort Jackson, N.Y. have been declared unsafe for drinking by the New York State Health Department. A monitoring system was set up to test selected wells and springs, along with a stream passing next to the community, to try to determine the source and severity of contamination. Most tested residential water supplies have 3-12 ppm NO3-N, and most have had one or two positive tests for coliform bacteria over the three month test period. Significantly, the spring that has had the highest NO3-N readings (12 ppm) is located above the community. Two other residences, both with drilled wells and each located over half a mile away from the community, also have elevated concentrations of nitrates. The stream, tested at 3 locations, consistently contains <1 ppm NO3-N, but the farthest upstream location, well above the community, consistently tests positive for coliform bacteria. These data indicate that the major source of nitrate and coliform bacteria contamination must be external, and not from local septic systems.