R2024-297 Resolution Rescinding R2024-282 and Authorizing a Real Estate Sales Agreement for Properties between Vulcan Lands Inc., and Vulcan Construction Materials, LLC, and the City of Decatur

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Executive Summary Inherent uncertainty in future growth and climate conditions can complicate decision-making regarding investments in water supply improvements. The goal of this study has been to analyze the City of Decatur's (City) water supply options and identify a path toward a future water supply portfolio that is reliable, resilient, and affordable. Average monthly water demands for the City and primary industrial users were projected out to year 2050 based on population projections and a statistical analysis of the relationships of per capita use and weather conditions. Hydrologic records were compiled and analyzed for historical drought periods. A 10-month duration design drought for Lake Decatur was produced by combining the early summer drought conditions of 2012 with the drought of record (1930-31). A water-budget model of Lake Decatur was developed, based on post-dredge lake volumes, hydrologic inputs, and lake withdrawals for water supply. The model was used to evaluate the supply gap. The supply gap is defined as the difference between water available in Lake Decatur amd the water demands during a drought. During the ten-month design drought, the water supply available from Lake Decatur with current minimum lake elevations will not meet the projected demand. An additional water supply of 3.1 billion gallons must be obtained. The largest additional source could be provided by Lake Decatur itself, by lowering the minimum lake level from the current elevation of 607 feet to 604 feet. This change in minimum operating level maximizes the benefits of the lake dredging project. This change will provide an additional supply of 1,670 MG. However, modifying the minimum lake level impacts operations of ADM's NWTP. Below a lake level of 607 feet, the NWTP intakes are inoperable. The result is that the City would have adequate supplies to meet potable demand from the SWTP, but ADM's non-potable supply would not be available. Currently, the City has access to an additional 880 million gallons (MG) in its water supply portfolio, which includes the DeWitt well field (630 MG) and the former Vulcan Pit (250 MG). Lake Tokorozawa (900 MG) has been used by the City as a drought supply in the past, but the lake is not equipped as a permanent supply. The portfolio that best meets the needs of the City will balance cost, reliability, resiliency, and stakeholder considerations. One recommended portfolio that would adequately address the combined (City and ADM) supply gap includes: • Lake Decatur 604 ft Minimum Operating Pool - Alternative 1A, • DeWitt Well Field Improvements - Alternative 2A, • Former Vulcan Gravel Pit Improvements - Alternative 3, and • Lake Tokorozawa Direct Intake - Alternative 4A Figure A illustrates the recommended portfolio that includes Lake Decatur, DeWitt Well Field, and Former Vulcan Gravel Pit, plus potential development of supplies from Lake Tokorozawa. i