Being recognized for our project teams’ efforts is always noteworthy to us—the acknowledgement for a job well done is a great reminder of how our work benefits our clients and communities. It was particularly exciting to have received an ACEC Georgia Engineering Excellence Award in the Water/Wastewater category for our work on Delta Air Lines’ Wastewater Treatment Plant Upgrade Project at the Hartsfield-Jackson Airport in Atlanta.
While wastewater plant renovations projects always come with their share of challenges, on this project our team faced a significant added level of complexity: working on a project site behind security in the world’s busiest airport.
The Hartsfield-Jackson Airport has been known as the world’s busiest airport for nearly two decades, with the highest amount of passenger traffic and aircraft operations recorded yearly. Delta Air Lines is headquartered in Atlanta, and its main maintenance hub, the Technical Operations Center (TOC), is located there, consisting of aircraft maintenance; repair hangars; and engine repair, engine test cell, plating, aircraft painting, and carpentry shops. This project took place at one of the four Industrial Wastewater Pretreatment Facilities there that Delta uses to pretreat wastewater generated from aircraft maintenance activities for discharge to the City of Atlanta sewer collection system—the Oily Water Treatment Plant (OWTP).
Plant renovations for increased redundancy
The OWTP treats 300,000 gallons per day of wastewater originating in various maintenance areas and shops. For the past 17 years, Woodard & Curran has partnered with Delta to perform all operations and management at this facility, performing several improvements throughout the years. Prior to this project, wastewater at the OWTP was treated using screening, grit removal, primary clarification, biological treatment in a mechanically aerated oxidation ditch, and secondary clarification before being discharged. Much of the equipment and unit processes involved, though, hadn’t been upgraded since the plant’s original construction in the 1970s. During a regular assessment in 2011, we identified a lack of redundancy in both the biological treatment and secondary clarification operations; if either one failed, Delta would have to transport wastewater off-site for treatment.
The project involved repurposing one of three equalization tanks to an aeration tank employing diffused aeration. This provides redundancy for biological treatment as well as a more efficient and maintainable biological process than the former oxidation ditch, as the new aeration blowers provide oxygen more energy-efficiently and are equipped with automated speed control from dissolved oxygen instruments in the tank. A new secondary clarifier was also built above grade on top of an out of service in-ground oxidation ditch as part of this project. Its design makes the new clarifier easier to operate and maintain, and the cost to build the tank above ground was less than an in-ground construction due to unfavorable subsurface conditions. In fact, once the old ditch had been removed, the area had to be preloaded to pre-settle the unfavorable subsurface soil before the new clarifier could be built.
Achieving success in a secure area
The TOC, where the OWTP is located, is in a secure environment at the airport that involves a three-tiered badging system for permitted access, from the highest level—a SIDA badge, issued by the TSA—to the lowest level—a visitor’s pass, which requires its users to be in the line of sight of higher badged personnel. While this system makes good sense from a security perspective, the nature of the work and the project’s multiple components made this a real logistical challenge, requiring a great deal of back and forth from the job site to security checkpoints to escort workers with visitor badges and training new employees from subcontractors once their visitor badges expired after three days.
Another challenge at the project site was conducting work so close to the runway. Preloading the site of the out-of-use oxidation ditch required hauling debris out and preload soil in and out around operating aircrafts, making foreign object debris (FOD) a major concern—very small objects can cause significant aircraft engine damage. To work around this, we avoided conducting major hauling operations during the day shift, opting for night shifts when there was less traffic within the TOC. Night operations require redoubled safety and security diligence, as well as another set of logistical challenges. For instance, though lights were necessary to conduct the work at the site safely and effectively, no lights could shine toward the air traffic control tower or planes.
This project is a great example of the ways in which a design-build approach can help a project succeed. “Not only were Woodard & Curran and their team of subcontractors and vendors up to the task of managing the complex airport safety and security challenges placed on them, but they completed the project on budget and ahead of schedule, all while keeping the existing oily waste treatment plant in compliance,” noted our primary partner at Delta, Joshua Smith, Manager of Environmental Health and Industrial, Global Environmental, Compliance and Sustainability. This was due at least in part to our design-build approach, combined with the highest level of teamwork, flexibility, and smart design choices. Delta anticipates this project will position the OWTP well to incorporate further improved technologies for innovative and environmentally sustainable wastewater management strategies in the future.
