Case Studies 07-22-2022
Halff worked creatively and strategically with the City of Bull Shoals, Arkansas, to design and replace the existing wastewater treatment plant, which included upgrades to the current collection system. This effort, adjacent to the White River, was honored as the top project in the Water and Wastewater category of the 2021 ACEC Arkansas Engineering Excellence Awards. The replacement of this 50-year-old facility accomplished many objectives without compromising the safety of the river and its environment.
The firm not only executed the improvements, but also assisted the City in securing $9 million of grants and loans to fund the project. A USDA grant provided $4 million of the funding. Located within a town of only 2,000 people, the Bull Shoals project required close collaboration to obtain funding. In addition, Halff developed a comprehensive Preliminary Engineering Report (PER) for the City to use in pursuing project funding. The PER included an environmental impact assessment of the project options and preliminary cost estimations.
Bull Shoals Wastewater Treatment Plant is a very environmentally friendly treatment facility due to its location next to the White River, downstream of the Bull Shoals Lake dam. The river is one of the country’s most highly used rivers for recreation and trout fishing. Pristine waters flow through this river, maintaining the beautiful ecosystem in the area. Not only is the White River popular, but it is also one of the most environmentally sensitive rivers in the United States.
It was imperative to maintain the cleanliness and purity of the river throughout the project, while delivering the much-needed additions and improvements.
The project posed several large challenges to Halff and the City:
The Bull Shoals Wastewater Treatment Plant is unique because it incorporates dual capacity in the treatment process, allowing future maintenance to be performed on units of treatment while maintaining full treatment capacity. This allowed Halff to focus on delivering the improvements and replacements without halting the wastewater treatment plant processing.
The aeration/activated sludge process takes place in two separated circular tracts to allow dual capacity. The secondary clarifier engages in the same process, and multi-disk filters provide treatment while any filter disk is being serviced. The existing treatment plant was deactivated and demolished after the new plant was brought online, meeting all compliance testing discharge monitoring requirements. The new treatment process was meeting all discharge water quality testing within days of start-up.
This project also included replacing sewer collection lines and manholes, as well as upgrading and reconstructing 18 sewer pump stations. The reason for so many pumps is the treatment plant is located on a ridge with uneven landscape. All pumps are required for proper functioning.
Not only did the project replace corroding steel components, its design had to guarantee the new plant was remained environmentally safe and adaptable for future improvements and expansion.
Halff Vice President Mike Marlar, PE, explained how the new plant needed to be one structure. “Concrete is less prone to corrosion than the old steel plant,” he said. “And more sympathetic lighting was required because just across the river is one of the most popular campgrounds in Arkansas.” There were many major factors to consider within this project, including the townspeople and White River campers, that Halff tactfully accounted for.
Results and Benefits
Collaboration for this project was extremely important, as Halff worked closely with the City and area residents. Everyone poured in a great amount of care for Bull Shoals, as even the townspeople took great interest in the project and outcome. From securing funding to communicating project progress, everyone worked together as a team each step of the way.
The Halff team completed the project design in the spring of 2018. Attention to detail was imperative during this design process. The design team’s primary goals were to develop a grading plan that conformed to the rugged terrain and protected the adjacent White River during construction. The design allowed the existing plant to stay in service until the new plant was activated.
The new treatment plant uses mechanical screening; grit removal; a combined aeration/activated sludge process and clarification in one circular tank; secondary clarification; multi-disk filtration; ultraviolet (UV) light disinfection and flow measurement.
The rehabilitation of the existing collection system includes open-trench replacement of more than 1.5 miles of existing sewer mains. The mains selected for replacement follow the alignment of valley streams that drain to the White River. The decades of erosion at the treatment plant resulted in vulnerable mains, liable to inflow and infiltration (I&I). The new lines were designed with adequate cover and watertight manholes to reduce the City of Bull Shoals I&I issues.
After the groundbreaking, Halff assisted the City of Bull Shoals with construction and contract management. In addition, Halff handled all the project reports, pay requests, change orders and close-out documents. The firm provided full-time construction observation throughout the project. The construction was completed in 2020 and the project received the 2021 ACEC Excellence in Engineering award.
Dr. David Nixon, the mayor of Bull Shoals, has expressed how visitors comment on the aesthetics of the outstanding new facility.
Halff safely and securely delivered impressive improvements and quality work to the Bull Shoals Wastewater Treatment Plant. Through award-winning design, close collaboration between Halff and the City, and excellent expertise, the project delivered many wonderful improvements and solutions to maintain a brighter and cleaner future for the White River and the community.
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