Groundwater Modeling Projects
Columbus, Ohio South Well Field - Master Plan: This project involves development of a long range plan to maintain the integrity of three radial collector wells along the Scioto River. Eagon & Associates, Inc. has analyzed alternatives for the continuing water source for the Parsons Avenue Water Treatment Plant as ongoing aggregate mining operations in a limestone quarry encroaches upon the 50 million gallons per day well field. In order to evaluate the future impacts and various mitigation measures, Eagon & Associates, Inc. has developed finite-difference and finite-element groundwater flow models based upon previous modeling studies performed by Eagon and the U.S. Geological Survey. The model has been expanded to encompass the watershed that drains to the well field area and includes the active sand and gravel and limestone quarries that are within the well field area. Various stages of aggregate mining were simulated with the model, including quarry dewatering and pumping into gravel pits to recharge the aquifer in the vicinity of the collector wells. Each scenario was analyzed to evaluate potential impacts on collector wells, existing private wells, and the overall water balance components such as quarry pumpage and recharge rates. Work is currently ongoing to update the model and conclusions based on new data provided by ongoing operations.
Columbus South Well Field Expansion: This project involved well site selection, design, and construction oversight to establish five new well-field sites; two in southern Franklin County and three in northern Pickaway County. Eagon & Associates reviewed the data and reports for pumping tests performed at all five sites and developed a test-drilling program designed to finalize actual well sites and determine a final well design for each site. Test drilling by cable tool, mud rotary, and rotosonic methods was completed, samples were selected for grain-size analysis, and information was evaluated to determine whether vertical wells or radial collector wells would be most appropriate at each site. Preliminary design reports were prepared for each site, including updated hydrogeologic cross sections and calculations to estimate safe yield potentially available. A groundwater flow model was prepared for the Pickaway County sites to evaluate the mutual interference between well-field sites and to determine the ultimate capacity to be expected from that area. In addition, the potential impact to be expected on existing private wells was evaluated using the groundwater flow model.
Hydrogeologic Evaluation of Quarry Lakes at Gibsonburg, Ohio: The objective of this project was to evaluate the impact of water levels in quarry lakes that would likely occur if used as a water-supply source. The Village of Gibsonburg owns two quarry lakes from which limestone was mined until about 1983. After mining activities ceased, the quarry pits filled with water from the bedrock aquifer. After reviewing all available historical information, Eagon & Associates, Inc. developed a computer model to evaluate inflow and outflow relationships between the quarry lakes and the bedrock aquifer. Extensive sensitivity analysis was performed to determine which input parameters were critical to the evaluation and various scenarios using parameters deemed most reasonable based on available data. It was concluded that a sustainable yield of 1.2 MGD could be obtained with less than 7 feet of water-level drawdown in the quarry lakes and nearby wells. Recommendations were provided for subsequent testing in order to validate or refine model predictions.
Akron OCI Tunnel Project: Eagon & Associates, Inc. performed a 72-hour pumping test in order to gain information on which to base an evaluation of dewatering feasibility and cost to dewater an excavation for a proposed storage basin. A groundwater computer model was developed from the test results and data from the geotechnical investigation for the site. Values for groundwater recharge rate, hydraulic conductivity, specific yield, and riverbed conductance were refined by parameter estimation process until a reasonable fit was obtained between measured water levels and drawdowns and those computed by the model. Various dewatering scenarios were simulated to determine the optimum number and spacing of dewatering wells and pumping rates required to keep the excavation dry during a three year construction process. The initial design proposed was changed substantially during the design process and additional simulations were provided to design engineers as various means and methods were analyzed and dewatering requirements and estimated costs were revised accordingly.
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