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Council to consider approval of super-sized sewer

Tuesday, November 17, 2009 by Bill McCann

A super-sized sewer that will accommodate continued growth in and around downtown Austin for the next 50 years is on the City Council agenda for approval Thursday at nearly half the initial estimated cost.


The Austin Water Utility is seeking approval of a $32 million contract (plus a $3.2 million contingency) with the low bidder, SAK/Quest Joint Venture of O’Fallon, Missouri, to build the 3.5-mile Downtown Wastewater Tunnel. If the project is approved, work will begin in January and be completed in about two years.


The initial engineering estimate to construct the project was about $58.6 million (with no contingency included). The contract bid represents a drop of $26.6 million, as competition for contracts during the recent economic downturn has continued to result in lower bids for many construction projects. 


“The project will be a big benefit because it will take care of downtown-area growth, while eliminating the potential for overflows into the (Lady Bird) lake,” said Gopal Guthikonda, the water utility’s assistant director of engineering services. “We think it will be a good deal for the city and the environment.”


The new tunnel would vary in diameter from 8 to 10 feet – big enough to fit a car. It would be between 45 feet and 70 feet underground, starting from near the intersection of Lamar Boulevard and ending at an existing tunnel near the Kreig ball fields in East Austin. Along the way it would dip under Lady Bird Lake (Colorado River) three times and would go under Interstate 35. The existing tunnel near the ball fields connects to the South Austin Regional Wastewater Treatment Plant.


The new wastewater tunnel would relieve two existing primary sewer lines, or interceptors, that extend north and south of the lake and are at or near capacity, according to Guthikonda.


In addition, the tunnel will eliminate sewage lift stations at Toomey Road and Shoal Creek, thereby ending the possibility of sewage overflows during periods of high flows such as heavy rains, Guthikonda said. The Shoal Creek lift station has been a weak point, where overflows have occurred in the past during high flows. With the new tunnel in place, there would no longer be any lift stations all the way from Barton Creek to the wastewater treatment plant.


The area covered by the new tunnel project is projected to increase from 93,183 residents in 2000 to 153,444 in 2060. The downtown portion is projected to double in size from 18,370 residents to 35,071. 


The project was conceived more than a decade ago. The downtown master plan in 2003 included route alternatives and preliminary engineering. One alternative that was initially considered was to dig trenches and install bigger lines to replace the existing interceptors. But that alternative would have meant considerable disruption to homes, business, and traffic and could have caused environmental problems when crews dug trenches near and along the lake.

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