Located in Fulton County outside Atlanta, GA, lies a 24-mgd water reclamation facility known as Big Creek WRF. The facility has been an asset to Fulton County (owner) for over 50 years, treating flows from the ever-growing population and business expansion within the area. Its current treatment process is based on a traditional, activated sludge process discharging into the Chattahoochee River. Over the years, it has been a reliable facility, with awards lining the administration building for exceptional environmental compliance and operational excellence. However, as the adjacent properties have been developed, it has lacked some of the more “neighborly” features of a modern facility – including effective odor control, noise reduction, and light pollution mitigation. With development increasing in the North Fulton area, regulatory discharge limits decreasing, and the age of the existing plant, the County has embarked on a full-scale upgrade of the facility utilizing the progressive design-build delivery model. The design-build team of Archer Western Construction and Brown and Caldwell are delivering the project.
The initial capacity was set at 38 mgd and the process will be changed to membrane bioreactor to meet the long-term reduction in nutrient discharges anticipated to meet permit compliance. Fulton County also insisted that the facility become known for being a good neighbor and not a nuisance that impacted the surrounding area. This means that no odors are to be detected at the property line, noise from equipment and traffic on site will be confined, and light necessary for operations will not pollute the skyline. These objectives were chartered with the project team and have become an ever-present component of all decision-making throughout the design development.
Retrofit Existing or Build New
One of the greatest advantages of the progressive design-build process is the ability to empower the project decision makers with real-time cost comparisons during the initial programming phase. As the project began, the team was faced with one of the most critical decisions for the success of the project – to retrofit the existing structures or to build new? Multiple scenarios were generated by the design-build team to compare a complicated phasing approach of working inside of an existing facility versus constructing all new structures on an adjacent area of the property currently unused. As the design-build team presented the design options and associated cost models to the county, it became apparent that the construction of new facilities would be more cost effective and provide greater value over the life cycle of the project. This included the ability to adjust the hydraulic profile of the plant to provide a full gravity process flow through the membranes, minimize the hauling of spoils off-site, and reorienting the headworks and sludge dewatering processes to the middle of the site in order to confine the noisiest and most odorous processes. All of these features, combined with a faster schedule that is less susceptible to the delays of retrofitting existing structures, led to the decision to move forward with the design of a new state-of-the-art facility on site.
Selecting a Technology Provider for the Membrane Bioreactor (MBR)
The DB team and owner continued to employ the benefits of the progressive model by developing a full-scale solicitation to select the MBR technology provider during preliminary design. The resulting RFP not only included capital expenditure and long-term operational costs, but the associated cost of constructing the elements necessary for each supplier’s equipment. This process again empowered the owner with the information necessary to select the technology that would provide a reliable facility that is easily operated and maintained, while permitting the DB team to optimize the design around a specific technology provider.
Getting a Head Start on Construction
Leveraging yet another benefit of the PDB model has allowed the project team to get started on an “early works construction package” which will prepare the site for the new facility while the design is progressed to 80% and GMP is completed. This work includes numerous utility relocates, demolition of decommissioned structures, earthwork activities that will remove a large pile of spoils and construction debris from previous upgrades, and deep foundations that will provide the necessary support for the future structures. The result of this work will shorten the overall project schedule and completion date.
The implementation of the progressive design-build delivery model continues to provide benefits to the project while keeping it in line with the objectives set nearly two years ago. Thanks to a dedicated team and a decisive owner, the progress to date has been significant, and the team is well positioned to move into the next phase of the project. Construction of the large-scale expansion is officially underway and expected to follow a 46-month schedule, concluding in 2024.