Hampton Roads Sanitation District's Atlantic Treatment Plant, which has a permitted design capacity of 54 million gallons per day, operates as a high-rate activated sludge plant that is able to achieve biological oxygen demand and total suspended solids removal. With this project, the team aimed to produce Class A biosolids product and provide for future increases in solids handling capability. All of this had to be achieved without increasing digester capacity. A new fats, oil and grease receiving station also needed to be integrated in the thermal hydrolysis process treatment process.
As construction manager at-risk, Crowder was integrated into the preconstruction phase as well as managing the construction. The project underwent significant value engineering, with innovative ideas to use existing real estate proving key to cost savings and overall project footprint reduction. This effort included repurposing the plant's abandoned dissolved air flotation thickening room to a multipurpose space that would house the nonpotable water filtration, solids screening and conveyance, solids bypass piping and a new electrical room. Additionally, the existing dual hot water boiler room was converted to house a new steam boiler, deaeration system, steam distribution and heated nonpotable water system.
Photo courtesy Crowder Construction Co.
A new predewatering building was also added, which mitigated constructibility concerns by placing centrifuges inside the existing gravity belt thickener room. The building's placement was a significant challenge on a compact site with limitations created by previously surcharged soils. The team brainstormed concepts with the client on how to fit the large facility into a compact space to eliminate piles and reduce costs.
Furthermore, Crowder reviewed the owner's planned approach to digester cleaning, offering an alternative and upgraded sequence. As a result, the overall timeline of the project was reduced by nearly six months, allowing earlier access to more critical digester facilities and reducing the number of times a particular digester in the sequence had to be temporarily removed from service. The six-year project was completed on budget in December 2023.