Planned tunnel should keep sewage out of waterwayss
5.10.11

INDIANAPOLIS STAR

The city is going to great depths to eliminate billions of gallons of raw sewage overflows from overburdened treatment plants into the White River and other waterways each year.
Officials said Monday the city will seek bids May 16 on an estimated $300 million deep-rock sewer tunnel, its most expensive infrastructure project to date. Construction could start by September on the 18-foot-wide, seven-mile sewer.
Cities with aging sewer systems often have combined storm water and sanitary sewers. When it rains heavily, treatment plants can't handle the additional water, and untreated sewage flows into rivers and streams.
The tunnel will be able to store 54 million gallons of sewage, stopping it from reaching waterways. And it's being buried deep -- 250 feet down -- so groundwater can't seep in and add water to treat.
It's the first in a five-tunnel system, part of the city's estimated $3.1 billion in planned upgrades. Many of those will comply with an agreement with the U.S. Environmental Protection Agency and the Indiana Department of Environmental Management to nearly eliminate overflows from the city's combined sewers.
The federally mandated Clean Water Act and state law require all communities to update combined sewer systems. Central Indiana communities such as Noblesville and Speedway, which also have antiquated systems, also have begun projects to address overflows.
To pay for this phase of Indianapolis' 20-year sewer plan, the City-County Council in 2009 approved a 66 percent increase in sewer rates over four years.
Kevin Hardy, executive director of Friends of the White River, said the tunnel will address a problem that's needed a solution for years.
Consider this: On April 30, Hardy was part of an effort that removed 23 tons of trash from the White River. But volunteers couldn't remove one of the worst pollutants -- the 7 billion gallons of raw sewage that enters waterways every year during heavy rains.
The first tunnel will cut that overflow figure in half. When four similar tunnels are finished elsewhere in the city by 2025, the overflow will be down to 414 million gallons.
"We don't have mountains," Hardy said. "We don't have a bay or beaches. The river is right here in the midst of our urban setting, and it's a very beautiful waterway that needs attention and improvement."
Tom Iseley, a professor of construction engineering management technology at Indiana University-Purdue University Indianapolis, said the city's planned tunnel is a proven, cost-effective solution. He said similar projects have been completed in cities such as Atlanta, Chicago and Milwaukee and have proved more effective than building separate storm water and sanitary sewers.
"It brings to the city an option that has a high level of success in cities with major issues (with sewer overflows)," Iseley said.
Mayor Greg Ballard's office has been touting a $740 million savings from that original plan from recent engineering changes. Steve Nielsen, deputy director for the Department of Public Works, said building deep-rock tunnels will cut down on costs that could have been incurred to further expand other parts of the sewer system to better handle overflow.
Nielsen said commuters and residents needn't worry about construction headaches, because he doesn't expect any significant road closures or restrictions. And the tunnel will be buried so deeply, he said, it's likely many people won't even know the project's under way.
But engineers say anyone standing directly over the part of the tunnel that's being bored could feel a slight vibration -- although not strong enough to, say, knock items off a shelf.
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