Water Online the Magazine gives Water & Wastewater Engineers and end-users a venue to find project solutions and source valuable product information. We aim to educate the engineering and operations community on important issues and trends.
Issue link: http://wateronline.epubxp.com/i/557891
'Project Clean Lake' Breaks New Ground In Pollution Control The Northeast Ohio Regional Sewer District's $3 billion pollution-control plan includes massive and lengthy tunnels but goes the extra mile by adding advanced wastewater treatment. By Michael Uva I n 1972, the Clean Water Act was created to address the nation's water-quality issues, among them the foul spectacle of raw sewage discharging into the environment. In Cleveland, the Northeast Ohio Regional Sewer District's construction projects during the following decades would reduce these discharges significantly — from an estimated 9 billion gallons a year down to 4.5 billion in 2013. However, in 1994, the U.S. EPA adopted a Combined Sewer Overflow (CSO) Control Policy, which required wastewater agencies to develop long-term CSO-control plans to further reduce overflow. Cleveland and hundreds of cities around the country have negotiated long-term plans with the EPA to address sewage overflows. Fighting Overflow Why do overflows occur? The combined sewers prevalent in older cities carry both sewage and stormwater. When heavy rains overload the combined sewers, relief points within the sewers (known as regulators) allow the untreated stormwater and sewage to overflow into area waterways to avoid backups and home and street flooding. This CSO contains bacteria from human waste, industrial waste, and other pollutants swept from the ground's surface. Following rain events, Cleveland's beach- goers are often advised not to go swimming in Lake Erie due to elevated bacteria levels that accompany CSOs. Project Clean Lake is the sewer district's $3 billion, 25-year program to reduce the total volume of CSOs in Cleveland from an estimated 4.5 billion gallons annually to less than 500 million gallons. By 2035, the number of overflows will be reduced to four or fewer per year, resulting in an estimated 98 percent capture and treatment of all wet-weather flows in Cleveland's combined sewer system. At the heart of Project Clean Lake is the construction of seven large-scale storage tunnels, ranging from two to five miles in length, up to 300 feet underground, and up to 24 feet in diameter — large enough to fit a semi-trailer truck. This technology is widely used in CSO-control plans across the country. The tunnels can hold tens of millions of gallons of CSO, rather than allowing it to discharge into Lake Erie and the Cuyahoga River. After the rain stops, massive hydraulic pumps convey the flow back to the surface and to one of the district's three wastewater treatment facilities. In April 2011, the sewer district broke ground on its Euclid Creek Tunnel project, which includes an 18,000-foot-long, 24-foot-wide storage tunnel 200 feet underground. Just over two years later, in August, 2013, "Mackenzie," the district's 1,500-ton tunnel boring machine, completed its three-mile- long excavation. The finished tunnel will have the capacity to capture about 65 million gallons of combined wastewater and stormwater and will directly impact water quality in Lake Erie and local streams. Project Clean Lake also includes a minimum of $42 million in green infrastructure projects, which the federal government had never before included in its CSO-control consent decrees. These stormwater-control measures, which include such technologies as bioswales and detention basins, can store, infiltrate, and evapotranspirate rainfall before it even makes its way into the combined sewer system. In the last five years, the sewer district has committed more than $31 million to green infrastructure projects. Plant Power Enhancements to the sewer district's three wastewater treatment plants, which together treat over 90 billion gallons each year, are crucial components of Project Clean Lake. At the district's Easterly and Southerly treatment plants, the amount of wastewater that can receive treatment will increase. This is necessary to accommo- date the greater volumes of combined flow that will no longer be allowed to discharge straight into the environment. In particular, the Easterly plant is undergoing major construction through 2016 to expand its secondary treatment capacity, including the installa- tion of six additional final settling tanks. Despite the ongoing construction, Easterly was recognized in 2014 with the highest performance honor from the National Association of Clean Water Agencies: the Platinum "Peak Performance" Award, for five consecutive years of meeting National Pollutant Discharge Elimination System (NPDES) permits. The Westerly and Southerly plants also received Gold Awards for continued excellence in meeting their NPDES permits. In addition, all three district plants are implementing advanced methods for dealing with wet- weather flows from overwhelming rain events. "Even with the new storage tunnels, you still can have 10 wateronline.com n Water Innovations Construction at the Easterly Wastewater Treatment Plant (March 2015) to expand secondary treatment capacity as part of the Project Clean Lake consent decree with U.S. EPA.