THREE DIMENSIONAL MODELING OF THE GROUNDWATER DISTRIBUTION WITHIN THE CORNISH HILL DRUMLIN USING ELECTRICAL RESISTIVITY, OSWEGO, NEW YORK

During the Spring 2007, high-resolution electrical resistivity surveys were completed over the eastern flank of the Cornish Hill drumlin, Oswego, NY, to develop a 3D groundwater distribution model. The Cornish Hill drumlin, located at Fall Brook Farm (SUNY Oswego) is one of scores of drumlins that make up the Pleistocene drumlin field in central New York. Ten (~100 m) roll-along Wenner array survey lines, spaced 20 m apart, were completed. Each line included two roll-along runs with each run having 24 nodes spaced at 3 meters. Pseudosections and 2D inversion models were generated for each survey, and the entire data set was merged to produce resistivity maps at varying apparent depths. The apparent resistivity readings range from less than 100 ohm-m to more than 450 ohm-m. Some parts of the drumlin had groundwater seepage and these regions were interpreted to be saturated in the shallow subsurface. Resistivity readings in these areas were generally low (50-150 ohm-m). Using this field correlation, the domains of low apparent resistivity were interpreted to be groundwater saturated, while domains of higher values were interpreted to be under-saturated. The low resisitivity anomaly is confined to the mid-section of the drumlin with high value anomalies near the base and top. If the field correlation between the resistivity values and groundwater seepage is correct, then the drumlin must contain a barrier to downward infiltration of groundwater. These results suggest that the internal distribution of glacial material is most likely sorted, and there must be a continuous layer that is probably clay-rich. Core will be collected at this located in the Spring 2008 to test this 3D groundwater model.