To reduce ambiguity in the analysis, five of the six subdivisions
selected are located in areas with little to no upgradient agricultural
activity or other known sources of nitrate-nitrogen.
Sampling Procedures of Water Supply Wells
Water samples were collected from inside or outside faucets of homes in
each of the six subdivisions. The samples were analyzed for nitrate-nitrogen
at the Wisconsin State Laboratory of Hygiene in Madison, Wisconsin. The
samples were analyzed for 615N by Roy Spalding, Ph.D. at the Water Center, 103
Natural Resources Hall, University of Nebraska, Lincoln, NE. The University
of Nebraska laboratory is certified by the U.S. Environmental Protection
Agency to conduct 15N analyses.
The wells selected for sampling had previously recorded values of
nitrate-nitrogen in excess of 10 mg/L or were wells of highest nitrate-
nitrogen within the subdivision. A larger number of samples were collected in
Sandy Knolls, Oak Park, and Mill Run subdivisions where a larger number of
private-water supply wells exceed 10 mg/L nitrate-nitrogen. Water samples
containing 10 mg/L or greater of nitrate-nitrogen were requested by Roy
Spalding of the University of Nebraska.
Water samples were collected following standard procedures. For
example, nitrate-nitrogen samples were collected from taps after flushing,
collected prior to any treatment system, placed in insulated and cooled
containers, and shipped to the laboratory on the day of collection.  For 615N
samples, one liter of water was collected, frozen, and shipped in styrofoam
containers the day of collection.  A duplicate 6SN~ sample showed a variation
of 1.1.