Lowe's Germantown Parkway, Memphis, Tennessee

Columbia Engineering was involved in this project from early conceptual design and construction cost estimating through final design, permitting and construction. The 84 acre site, located in the City of Memphis, was located almost entirely within the 100-year floodplain of the Wolf River including 31 acres of floodway. In addition, the site was host to several acres of wetlands associated with a lakebed and an oxbow lake that had been created by the channelization of the river. Lastly, Memphis Light, Gas & Water (MLGW) maintained two high-tension power lines throughout the site.

Columbia Engineering performed land planning and preliminary engineering for the overall site and detailed civil site design for the first phase, which consisted of a 177,400 square foot Lowe's store and 669 parking spaces. The detailed design plans also included rough grading for an outlet and a second phase. During the design phase, Columbia Engineering coordinated with the developer, the property owner, the tenant (Lowe's) and the developer's architect. In addition, Columbia Engineering worked with our own consultants which included a surveyor, a geotechnical engineer, a traffic engineer, a modular wall engineer, and a wetland consultant.

In order to raise the site above floodplain elevation and maximize the buildable area, Columbia Engineering worked with the geotechnical and the modular wall engineers to design and construct a retaining wall among the floodway limit.

Special design consideration had to be given to the location of utilities behind the geogrid-reinforced wall, the wall foundation and the stresses exerted by periodic flooding of the river. Columbia Engineering worked with the geotechnical engineer on the ramifications of various options to address differential settlement in the area of the oxbow lake, and it was determined that dynamic compaction was the most effective solution.

The most significant engineering hurdle was finding suitable material to fill the site. In cooperation with the geotechnical engineer and the wetland consultant, Columbia Engineering found a solution that not only addressed this issue but also the wetland issue. On a remote portion of the site, we proposed a deep borrow pit where the substrata was suitable for structural fill. During construction, the borrow pit was used as a sediment basin. Once the site was stabilized, the borrow pit was then converted into a wetland habitat with peninsulas and ledges at the pool elevation. Wetland soils that had been stockpiled on-site were transplanted to the wetland area and wetland vegetation was established. Upon completion of the project, the created wetland and floodway were deeded to the local wildlife conservancy.

Columbia Engineering permitted the project through the City of Memphis and obtained permit revisions as requested by the developer. During construction, Columbia Engineering reviewed submittals, quality control reports and draw requests, and worked with the contractor and the owner's construction manager to resolve construction issues.