This report describes detailed groundwater investigations conducted in a sub-region of the Hillman Creek (PLUARG AG-13) watershed. The objectives of the investigations were: 1. to determine the distribution in groundwater of nitrate and to relate this to the observed distribution of land use practices 2. to obtain information on the mechanics of nitrate storage and transport in the groundwater zone 3. to develop procedures for predicting the rates at which the nitrate which is presently in subsurface storage will be transported into streams that drain to the Great Lakes 4. to develop relationships that can be used for extrapolation of at least some of the results from the detailed study area to other areas in the Great Lakes drainage system. Although nitrate was studied in detail, ammonium, phosphorus, potassium and pesticides, all potential agricultural contaminants, were also investigated.