By Ron Sparks
Nearly into its fourth year of construction, the East Side Combined Sewer Overflow Tunnel Project in Portland, OR, will greatly reduce combined overflows to the Columbia Slough and Willamette River. This is the largest construction project in the city’s history and Hanson Pipe & Precast has been involved since its inception, providing more than 6,000 feet of reinforced concrete pipe to make the project a reality. Scheduled for completion in 2011, the project is expected to reduce the volume of combined sewage and stormwater overflow drained into the river by more than 94%.
The East Side Combined Sewer Overflow Tunnel Project, also known as the East Side Big Pipe Project, is being constructed by Kiewit-Bilfinger Berger, a joint venture partnership. Mandated by the Federal Environmental Protection Agency to keep sewage out of the Willamette River, the $464 million Big Pipe Project will allow the sewer system currently in place to meet the future capacity of the city of Portland. Upon completion, the project will separate stormwater from sewage, as well as provide storage capacity for material waiting to be processed. This will allow water that would otherwise surge into the system to be processed and released into the river.
Hanson began producing pipe for the project in 2003 from its facility in Tualatin, OR, about 15 miles southwest of downtown Portland. The facility is manufacturing 6,200 feet of 84" × 10' ASTM C76/4 microtunnelling pipe with a zinc-coated steel bell on the jacking pipe. Concrete was the ideal choice for a project of this magnitude because of its design strength and structural capabilities. It is also able to accommodate the exceptionally long distances required for the job. D-load testing of Hanson’s 72" and 84" diameter pipes is performed in accordance with Section 5.1.1 of ASTM C76 and Section 4 of ASTM C497.
Hanson’s microtunnel pipe – the longest on the west coast – offers ease of installation and superior pushing surface, designed to withstand a push from a steel bell while maintaining a sheer-resistant, watertight joint. A total of 3,000 feet of pipe will be pushed horizontally under the downtown area, approximately 200 feet deep.
The sewer tunnel will be 22 feet in diameter and six miles long. The tunnel route will begin at SE 17th and McLoughlin Blvd. and will end on Swan Island where it will be connected to the Confluent Shaft. The Confluent Shaft connects to the Swan Island Pump Station, which will pump sewage through the Portsmouth Force Main, a pressurized pipe that Environmental Services will build as one of the East Side CSO projects. The force main will discharge to an existing tunnel, which will take the flow to the Columbia Boulevard Wastewater Treatment Plant.
Seven shafts are being built along the alignment. The shafts will connect existing overflow pipes to the East Side CSO Tunnel and provide aboveground access to the tunnel. The shafts will be approximately 49' to 60' in diameter and 110' to 165' deep.
The East Side CSO project, funded by sewer-bill ratepayers, is part of a long-range program to improve the city’s network of stormwater pipes and combined sewers. Hanson is working hand-in-hand with the project managers to install the city’s infrastructure without disrupting surface activities. The city estimates $1.4 billion for a system of much bigger pipelines and stormwater diversion systems along both sides of the Willamette and the
Columbia Slough.
Although CSO projects have progressed in many communities for years, the EPA’s Combined Sewer Overflow Control Policy was added to the Clean Water Act (CWA) in 1994 in an effort to mandate the upgrading of combined sewer systems (CSS). Many of these wastewater collection systems conveying water through a single-pipe system to a treatment facility were among the nation’s earliest built wastewater infrastructures and often overflowed during “urban wet weather” situations such as rainfall or heavy snowmelt. Using concrete pipe for the East Side CSO project will ensure installation ease and durability for years to come.
About the Author:
Ron Sparks is Hanson Pipe & Precast’s vice president and general manager for Oregon, Washington, Utah. He is based in the company’s western region headquarters in Portland, OR, and is responsible for managing daily operations including production and sales. He has 8 years of concrete manufacturing experience, all specifically devoted to the pipe and precast business.
