AN Aging infrastruc ture demands
23953.00 K U B Wastewate r sto r a g e Fa c i l i t i es Knoxville, Tennessee Engineering Sustainable Practice
big ideas. As is the case in many cities in the U.S., sections of Knoxville, Tennessee’s infrastructure included dilapidated sewer pipes—many more than 60 years old. During heavy storms, rainwater found its way into the aging sewer system via pipes and other porous entry points. The corroded system became unstable even during moderate storms, allowing a mixture of rainwater and raw sewage to overflow and enter nearby creeks and streams. The Knoxville Utilities Board (KUB) maintenance programs weren’t able to compensate for the rapid pipe deterioration. Finally, an Environmental Protection Agency (EPA) federal order mandated that the KUB tackle the problems immediately. KUB launched PACE 10, Partners Acting for a Cleaner Environment, in 2004 as an accelerated 10-year program aimed at helping to clean up Knoxville’s area waterways, improve citizens’ quality of life and support the city’s economic health. With over 36,000 customers, 30,000 manholes, 1,250 miles of sewer mains and 60 pump stations, the scope was daunting. KUB selected a program management team of CH2M Hill and GS&P to manage the design, construction and implementation of short- and long-term solutions to these problems. After repairing some of the most critical sewer lines and replacing others, the main focus of the plan became the design and construction of four wastewater storage tanks led by GS&P project manager Craig Parker, P.E. These would temporarily store excess wastewater during peak flows and reduce the incidence of sanitary sewage overflows. Commonly called equalization basins, the tanks are designed to automatically store excess wastewater once the trunk sewer reaches capacity. After the storm
subsides, the stored liquid flows back into the system for subsequent treatment. All of these basins have been built and put into service. Each consists of a concrete storage tank, a diversion structure located on the trunk sewer, a pump station to route the flow from the diversion structure into the storage tank, a grinder station, an odor control facility, an electrical building, and associated piping, valves and controls. One of the more complex aspects of the design was the system’s automation. Without operator involvement, electronic devices detect impending overflow, divert excess flow to the storage facility and then route it back into the collection system after the event has concluded. The facilities can be operated manually, if necessary, but normal operation is monitored by the KUB at a remote site. Of the critical success factors identified by KUB and the PACE 10 project team, the need for neighborhood-friendly designs was paramount. In response, the design team incorporated many aesthetic elements: screen walls with brick veneer, cast stone trim and standing seam metal roofing with curved rooflines;
ornamental wrought iron security fencing; brick and cast stone columns; and extensive restorative landscaping, including evergreen shrubs, trees and native grasses. Amazingly, all the elements were achieved while building in difficult geotechnical site conditions requiring rock anchors, thickened slabs to bridge-over mud seams, excavation of rock pinnacles and driven “H” piles.* The project has exceeded the client’s expectations by providing cost-effective solutions to the overflow problem while minimizing the impact on the surrounding areas. Both goals were achieved as a result of the GS&P design team’s close involvement with KUB personnel at all stages of the project, from conceptual design through construction. ■
MG = volume in million gallons MGD = flow rate in million gallons per day You’d have to flush your home toilet approximately 625,000 flushes to fill one million gallons of storage. A million gallons would be the approximate volume generated if everyone in Memphis, Tennessee, flushed simultaneously. *An “H” pile is a collection of H-shaped steel beams driven vertically into the ground in a cluster. Typically driven till the point of refusal then capped by a concrete slab, the beams become a solid foundation upon which to build.
Rain
Storm Drain
How does it work? When it rains and the treatment facility reaches capacity the tanks store excess wastewater during peak flows and reduce the incidence of sanitary sewage overflows. After the storm subsides, the stored liquid flows back into the system for subsequent treatment.
Wastewater
Treatment Facility Excess Wastewater
Storage Tank
Clean water
Walker Springs Storage Facility - 3.25 MG capacity - 14 MGD pumping capacity - Aboveground tank - Geotechnical issues - Dual electric power supply - Odor control
Lower First Creek Storage Facility - 5 MG capacity - 14.2 MGD pumping capacity - Expandable to 10 MG - Aboveground tank - Pump fill, gravity drain - Standby generator - Odor control
Third Creek Storage Facility - 4 MG capacity - 14 MGD pumping capacity - Aboveground tank - Pump fill, gravity drain - Dual electric power supply - Odor control
Upper First Creek Storage Facility - 9 MG below grade tank - 12.6 MGD pumping capacity - 6 MGD pump (empty) - Gravity/pump fill, pump empty - Dual electric power supply - Odor control
Gresham, Smith and Partners provides design and consulting solutions for the built environment that contribute to the success of national and international clients. For more than 40 years, GS&P has focused on enhancing quality of life and sustainability within communities. GS&P consists of industry-leading professionals practicing architecture and engineering design as well as scientists and highly specialized planning and strategic consultants in Environmental Compliance, Aviation, Corporate and Urban Design, Healthcare, Industrial, Land Planning, Transportation and Water Services. GS&P consistently ranks among the top architecture and engineering firms in the United States. For more information regarding GS&P, visit www.gspnet.com. Aviation Corporate + Urban Design Environmental Compliance Healthcare Industrial Land Planning Transportation Water Services
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