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Michelle Smith <br />May 9, 2019 <br />Page 3 <br />American Structurepoint proposes to perform the capture zone modeling (delineation) of the <br />North Wellfield wellhead protection area using the USGS finite -difference model MODFLOW <br />using the Groundwater Modeling System (GMS) engine. This type of groundwater flow model <br />meets the requirements of the Indiana Department of Environmental Management (IDEM). To <br />prepare the capture zone simulation, the following work elements will be performed: <br />i. Data Collection and Evaluation — Information needed to perform the capture zone <br />modeling includes development of an accurate conceptual model of the local groundwater <br />flow system and water supply production conditions. Data on the regional and local <br />geology, hydraulic properties of the aquifer, nearby water withdrawals, surface water <br />hydrology, and recharge will be collected through a review of relevant published reports <br />and field observations. The data collected will be assembled in a set of maps and cross - <br />sections and used for the development of the conceptual model. <br />ii. Conceptual Model - A conceptual model of the aquifer system is a graphical means of <br />identifying how groundwater moves in the subsurface under normal and pumping <br />conditions. A conceptual model of the local aquifer conditions supplying the North <br />Wellfield will be prepared to support development of the computer -based simulation <br />model. <br />111. Cuter Modelig g of Capture Zone — Using the conceptual model as an origin, the <br />aquifer properties and hydrologic information will be entered into the computer model, <br />and the flow simulation will be performed. Appropriate calibration of the model will be <br />completed, and the capture zone will be determined through particle tracking in the <br />model. Pursuant to current IDEM policy, sensitivity analysis of the model will be <br />performed through alteration of various hydraulic parameters (e.g., recharge, aquifer <br />flux), and a composite capture zone will be produced. The capture zone delineation will <br />include the one-year and five-year time of travel boundaries. <br />3. Potential Sources of Contamination Inventory <br />Based on the information provided to develop this proposal, an updated PSC inventory has not <br />been conducted recently. To prepare an updated inventory, we will review the most recent <br />inventory information and prepare a new potential source inventory, including the following: <br />a. Prepare base and layered ARC/View map coverages for the WHPAs, including: <br />i. Digitized delineated WHPA boundaries <br />ii. Locations of facilities permitted under the St. Joseph County Wellhead Protection <br />permitting program <br />b. Identify and map existing and new PSCs, including: <br />i. Review available database information to identify regulated sites within the WHPAs <br />ii. Conduct a "windshield" survey of each WHPA to identify unregulated or new PSCs <br />iii. Locations of new and/or existing PSCs will be incorporated into the GIS mapping. <br />c. Prepare a narrative description of existing land use within the WHPAs and an analysis of <br />changes in land use since the previous inventory <br />