HAYES, Mark H. ('98)   (Advisor: Bruce Selleck)

    Tully Valley is located south of Syracuse, New York on the northern edge of the Appalachian Uplands. The Valley is underlain by Silurian and Devonian shales, sandstones, limestones and evaporite-bearing shales and dolostones. Late Pleistocene till, lake clay and fluvial gravels overlie bedrock in the valley floor. The Valley Heads Moraine (elevation 1200 ft.) provides recharge to the confined aquifers in the valley. The moraine is a regional groundwater divide and forms the southern boundary of the flow system investigated in this study. The eastern and western boundaries of the flow system are shallow till-covered bedrock valley walls. Mudboils (artesian springs carrying suspended mud), saline/brackish surface springs, and continued ground-surface subsidence have been linked to unusual increases in groundwater potentials, perhaps related to past solution mining of evaporite-bearing bedrock (Kappel, et. al. 1996). Ongoing remediation of mudboil activity (which threatens the quality of Onondaga Creek) involves installation of wells which penetrate the confined aquifers and lower groundwater potential by pumping and discharge of water to Onondaga Creek. Saline spring discharge in the northwestern portion of the study area was significantly enhanced by a landslide in April, 1993 which disrupted the clay confining layer and permitted saline brines to flow on the surface, polluting the unconfined freshwater aquifer and surface runoff in the area.

    Previous efforts to model the groundwater flow system in the valley have focused on the small area adjacent to the mudboil discharge site and the confined brackish water aquifer. In this study, Visual Modflow (Waterloo Hydrogeologic) was used to construct a model of the entire valley flow system, including all known aquifers in the Pleistocene-Holocene sediments. The model has allowed us to examine flow patterns in the system and assess the effectiveness of existing remediation wells. The model permits analysis of the effects of depressurizing wells, and the resultant impact on mudboil discharge in the short term. The model can also be used to evaluate alternative remediation procedures such as limiting recharge from surface waters, as well as understand the long-term evolution of the aquifer system in Tully Valley.

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