Wastewater storage facilities play a critical role in mitigating sanitary sewer overflows and providing effective flow equalization for water reclamation facilities. Once a site is selected, one of the earliest design steps is to use hydraulic modeling to determine the required storage volume and the diversion rate needed mitigate SSOs. A second key decision is whether the storage facility should be constructed above ground or below ground. This decision can significantly influence cost, constructability, operations, maintenance, and public perception. Selecting the appropriate storage configuration is never a one size fits all decision. Elevations, hydraulic grade, flow and volume requirements, site constraints, geotechnical conditions, operations and maintenance considerations, and owner preferences all influence whether an above grade or below grade solution is ultimately implemented. This presentation will examine these factors through the lens of the City of Memphis’ Hillshire EQ Basin project. Initially designed as an above ground storage facility with an influent lift station, the project was later redesigned as a below ground facility with gravity influent as the final design. The presentation will compare the advantages and disadvantages of each design approach, review estimated capital and operation and maintenance costs, and highlight key lessons learned throughout the design and construction process. These insights provide practical guidance for engineers and owners facing similar wastewater storage decisions in constrained or evolving project environments.