Actual pumping and sampling will begin when the irrigation season starts, Ayers said. Eight multi-level monitoring wells have been constructed around the irrigation well after extensive study of the hydrogeological characteristics of the aquifer near Shelton in Buffalo County. At least one pumping test will be performed, more if irrigation schedules and weather permit, Ayers said. If all goes well, further testing will take place this fall and during the spring and fall of 1994, he added. Sampling of irrigation wells is quick, easy and relatively cheap, but the results may not be representative of the actual level of contamination because nitrate contaminantion isn't uniformly distributed in an aquifer, according to the team's proposal.
Nitrate concentrations tend to be highest near the water table and diminish with depth.
Thus, water sampled from a well that pumps from the bottom of an aquifer would show less contamination than actually existed. Using this data, they can then determine the relationship between pumping time and contamination in the aquifer. This information will help validate a computer model of contaminant flow in the aquifer. Five samples will be taken from each monitoring well before, during and after the experiment. Each experiment will yield up to 66 samples, which will be analyzed at UNL labs for nitrate contaminations.