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Exhibit A <br /> Statement of Work and Deliverable(s) <br /> = ILLINOIS Prairie Research Institute <br /> Illinois State Water Survey <br /> 2204 Griffith Drive,MC-674 <br /> Champaign,IL 61820 <br /> Assessing Sustainable Yield of the Mahomet Aquifer at the Decatur WeWields <br /> A Proposal to the City of Decatur,IL, <br /> August 2026 <br /> Vlad lordache(PI,Assistant Hydrogeologist) <br /> Daniel Hadley(Co-PI,Associate Hydrogeologist) <br /> Illinois State Water Survey(ISWS)Champaign,Illinois <br /> Introduction <br /> The City of Decatur has historically relied on the DeWitt Countywellfield as an <br /> emergency water supply during drought conditions and periods of low surface water levels <br /> in Lake Decatur.Past activations of this eight-well system,notably during the summers of <br /> 2005,2007,2011,2012,2025,and 2026 resulted in 30 to 50 feet of drawdown in the <br /> Mahomet Aquifer.The City is proactively planning for economic development,which is <br /> projected to increase overall water demand,prompting the City to quantify the sustainable <br /> yield from the Mahomet Aquifer. <br /> To support the City's proactive water management and infrastructure planning,the <br /> ISWS will evaluate the sustainable yield of the current DeWittwellfield and potential <br /> expansion areas.This modeling effort will run concurrentlywith,and provide critical yield <br /> estimates for,INTERA's Alternative Water Supply Plan Update.By quantifying the <br /> operational cone of depression and determining acceptable drawdown limits under various <br /> economic development scenarios,this project will provide the City of Decatur with a data- <br /> driven framework necessary to safely expand and manage their Mahomet Aquifer <br /> resources. <br /> Scope of Work <br /> Task 1:Groundwater Flow Model Refinement <br /> • ISWS will leverage its existing MODFLOW groundwater flow model of the Illinois <br /> River Basin,which encompasses the Mahomet Aquifer in DeWitt County. <br /> • Utilizing FloPy and Python-based scripting,a high-resolution inset model will be <br /> developed to evaluate pumping scenarios at a refined local scale. <br /> UNIVERSITY OF ILLINOIS URBANA-CHAMPAIGN <br /> 217.333.2210•isws.illinois.edu <br /> Page 8 of 9 <br /> SPA Form <br />