In April 2020, Carvana, a cutting-edge leader in online automotive sales, contracted Sain Associates to perform surveying, civil, and traffic engineering services for a distribution facility in Bessemer, Alabama. Although non-disclosure agreements required the project to be known as “Project Otto,” it was later announced as Carvana. Commonly known as an online car dealership and home of the car vending machine, Carvana designated this location as a distribution center. The facility is located on a 191-acre parcel of land, and the development contains a 190,000 SF building, a 532-space employee parking lot, 21.5 acres of paved space for car preparation and delivery, and 43.5 acres of paved space to store up to 7,200 vehicles. Of the 191-acre parcel, approximately 100 acres were disturbed for this development, and the remainder continues to be undeveloped greenspace.
This project required significant investment installing bottomless culverts over existing streams to maintain an existing stream bed while allowing construction for the distribution center, which created over 400 new jobs. Most of these stream segments were very narrow and could be stepped across, but in some areas, they had pools as wide as 16 feet. Our team looked at installing a conventional, large “arch” bottomless culvert across these streams; however, due to the broader stream segments and heavy loads, the cost of the arch culverts was several million dollars. Furthermore, we were filling significantly over these culverts, so the structural requirements were quite heavy and needed robust structural capacity to completely bridge and protect the stream while supporting the project. A typical project would have been delayed 12-14 months to obtain an Individual Permit from the US Army Corps of Engineers, but this project was under a fast-track design-build delivery schedule, so it did not allow time for such a lengthy permit process. So, we collaborated with the geotechnical and structural engineers to provide pre-cast reinforced concrete planks that could preserve the streams in place and stay on schedule with design.
We began by obtaining a detailed field survey of the stream alignment and widths, and we designed each bridge plank to fit together and span the varying widths of the stream. All these individual planks were pre-cast with lifting lugs, which allowed them to be carefully set in place and pieced together like a jigsaw puzzle that meandered along the natural stream.
The final bid from the contractor had a total installed price of approximately $1.75 million, which was much, much less than the $5 million estimated cost for using huge bottomless arch culverts. While the straight concrete planks are not as aesthetically pleasing as an arch culvert, they met the functional requirement, and they were buried beneath up to 35’ of fill material, so they were not visible.
We completed the project under COVID-19 restrictions, so remote collaboration was crucial to the project’s success. Due to the creativity and innovative thinking of our design team, we were able to complete the design and allow construction to be completed on time.