Cardno has designed several capital improvement projects related to the regionalization of wastewater collection and treatment within western Hernando County. Primarily, Cardno was the Engineer of Record for the design and permitting of the Airport Subregional Wastewater Treatment Plant (SWWTP) expansion. The expansion project was phased and initially included a capacity analysis and rerate from 0.75 million gallons per day (MGD) to 1.25 MGD. The existing effluent disposal system was also re-rated to 1.25 MGD subsequent to the design and expansion of the SWWTP onsite rapid infiltration basin (RIB) system.
The SWWTP expansion was then designed for an ultimate capacity of 6.0 MGD. The design included process, site/civil, mechanical, structural, electrical, and instrumentation/control design for new headworks, oxidation ditches, clarifiers, aerated sludge holding and dewatering, chlorine contact basin, sand filters, RIB effluent disposal, reclaimed water storage, and high service pumping facilities. Major deliverables comprised of Capacity Analysis Report, Capacity Rerate Report, O&M Performance Report, Preliminary Engineering Report, Land Application Report with groundwater modeling for expansion of RIBs, and Contract Documents including Project Manual (specifications) and Contract Drawings.
Subsequently, the completion of the design coincided with the decline of the economy, and construction of the project was deferred by the County. Portions of the expansion that still needed to be installed were bid and constructed as separate projects including the Sludge Dewatering Facility. Ultimately, the team was able to accommodate the County’s request to modify the design for construction of an expansion to 3.5 MGD without the inclusion of public access reuse facilities. Cardno provided full-time resident inspection services during construction of the expansion, which was successfully completed in 2016.