R2024-282 Resolution 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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8.10 Active Vulcan Pit - Alternative 7 (97% of Gap) This alternative entails the construction of direct intake pumping and pipeline facilities to convey water from the Active Vulcan Gravel Pit to the SWTP raw water pumping station. The estimated drought supply of this alternative is 3,000 million gallons (MG) per year, or 9,206 acre-feet (AF) per year. The active Vulcan gravel mine is located approximately 8 to 9 miles east-southeast of the SWTP (Figure 8.15). The City has discussed a Memorandum of Understanding (MOU) with Vulcan Materials in 2015, to establish the first right of refusal for site acquisition and interim rights to utilize water from the pit. Given the storage volume of the pits and the fact that it is downstream of the SDD WWTP discharge, the supply is assumed to be drought-resistant. The drought supply available from the pit is estimated to be 10 MGD for 300 days. Gravel mining operations are ongoing, and the projected duration of operation of the mine is 20 years or more. Water supply operations developed at this location would require coordination with the mine operator to ensure that appropriate Best Management Practices (BMP's) are utilized to minimize the risk of contamination. Water production from the pit could be accomplished via barge-mounted floating pumps with intakes, or by constructing horizontal wells adjacent to the pits to withdraw water from the aquifer. 8.10.1 Infrastructure The infrastructure required for this alternative includes 57,000 feet(10.8 miles)of 24-inch pipe,a 10 MGD barge-mounted floating pump station with intake,electrical service, a control building, monitoring wells, instrumentation and controls, SCADA integration, and miscellaneous site and security improvements. If the shallow downstream aquifer alternative (Alternative 5B) is also developed, there would be an opportunity for both supplies to utilize approximately 22,000 ft of shared pipeline, including highway, river and railroad crossings. 8.10.2 Operations It is estimated that the gravel pit will provide a drought-proof supply of 10 MGD for 300 days per year, for a total of three billion gallons per year. The quality of water supplied from the pit will generally be lower in nitrate and turbidity compared to Lake Decatur. Recommended operation of the water supply would be controlled by reservoir levels, with thresholds determined through decision support analysis. Pumping is also recommended when blending would be beneficial due to increased levels of turbidity or nitrate in Lake Decatur. The system will provide an important spill contingency supply for Lake Decatur if pumping from the primary intakes must be reduced. 116