Last-minute design change benefits Akron, Ohio, project
The Great Lakes region was blessed with abundant fresh water for its rivers and lakes. Water as a resource and method of transportation was an important factor in Akron, Ohio, blossoming as one of America’s manufacturing hubs during the late 1800s and early 1900s.
It was this industrial past that led to the pollution that caused the U.S. EPA to issue a federal mandate that compelled the city of Akron to end pollution in local waterways to comply with the Clean Water Act of 1972. Because about a quarter of Akron’s existing sewer system had been designed as combined sewers when constructed in the early 1900s, frequent overflows mixed storm water with sanitary sewage. This mix ultimately emptied into the Cuyahoga River, the Little Cuyahoga River, the Ohio and Erie Canal, and Lake Erie.
As part of the solution, Akron created a program called “Akron Waterways Renewed!” to control combined sewer overflow (CSO) and improve water quality in nearby rivers. A portion of that plan was to create a 6,240-ft Ohio Canal Interceptor Tunnel (OCIT), build three new storage basins, upgrade CSO racks, and upsize and reinforce the main outfall sewer cap. The 27-ft-diameter OCIT sections were a feat in themselves, dug with a massive tunnel-boring machine and constructed of reinforced concrete (RCP). The basins will hold combined sanitary and storm water overflow until it can be safely released to Akron’s wastewater treatment facility.
The design and construction of the influent line to the new Howard Storage Basin at the intersection of Howard and Cuyahoga streets, which will provide temporary storage of combined sewer flow from the North Hill tributary area, is of particular interest. With a 2.4-million-gal capacity, it is the largest of the three new storage basins.
H.M. Miller Construction, a civil and utilities construction contractor, was subcontracted for the site work for the Howard Storage Basin and one of Akron’s 34 sewer separation units, as well as relocating the existing waterline to accommodate influent piping. The H.M. Miller engineering staff saw a potential problem with the original design, which called for elliptical RCP influent line to run beneath Cuyahoga Street.
The staff realized it would be difficult to achieve clearance under the public road, even though the RCP line would be elliptical, and that could lead to inability of the RCP line to pass the required pressure test specification, according to John Smith, president of H.M. Miller Construction.
Smith called upon his resources at Hobas Pipe to assist in devising an alternate plan for the Howard Storage Basin that would resolve the inherent difficulties surrounding installation and testing using the RCP. Together they came up with a design that saved time and money tying the Howard Storage Basin into the main line. In place of the elliptical RCP originally specified to be installed under Cayahoga Street, the new design called for twin 57-in. Hobas centrifugally cast fiberglass-reinforced polymer mortar (CCFRPM) pipe that would tie into the OCIT-1 main line with a concrete collar subsequently designed by the project engineer.
Hobas provided 72-psi CCFRPM with FWC coupling; 100 ln ft of 84-in. FWC direct-bury pipe for the overflow sewer; 820 ln ft of 57-in. FWC direct-bury pipe that was jacked under Cuyahoga Street to form the twin-line influent to the Howard Street Basin; and 10 fittings that included various elbows, wyes and reducers.
H.M. Miller Construction had a 40 year history of contracts with Akron and had installed more than 11,540 ft of Hobas CCFRPM pipe in the Akron area since 2011. Respect developed over this long history between the firm, the public service department and local engineering firms, which encouraged the consideration and acceptance of this major design change during the construction phase, long after the engineering design had been completed.
Through teamwork, the owner (City of Akron), design engineer (DLZ/McMillen & Jacobs/Jenny) and construction manager at risk (Great Lakes Construction Co.) accepted the alternate plan submitted by the subcontractor.