Communities with combined sewer systems are caught between a rock and a hard place: building completely separate pipelines for wastewater and stormwater is an enormously expensive proposition for which federal funds are generally unavailable, and most EPA consent decrees allow just 20 years to pay off the bonds they issue to raise money. This usually results in rate increases that set residents howling. And often, says consulting engineer Vince Spada (www.seacon.com), the solutions don't appreciably improve water quality.
He recommends thinking outside of the box and looking for combinations of solutions—not just one. In 2004, when the Springfield Water and Sewer Commission (SWSC) (www.waterandsewer.org) signed its second consent decree with the EPA to eliminate combined sewer overflows (CSOs), Spada urged SWSC project manager Joshua Schimmel to ask for a "pause" so the agency could take a good, hard look at its system.
After collecting data from the field and flow data using hydraulic modeling, the Spada and Schimmel realized that some fairly inexpensive tweaks–such as clearing sediment-clogged pipes, removing baffles SWSC didn't even know existed, upgrading pump stations and an interceptor–could increase the system's overall capacity.
As a result, the commission's revised control plan, scheduled for completion May 31, 2009, is expected to remove 29 million gallons of runoff annually. It also eliminated three overflow storage tanks that had been in the first plan, saving nearly $8 million in construction and maintenance costs. For details, e-mail firstname.lastname@example.org.Session: "Selecting Combined Sewer Overflow (CSO) Controls"
Sea Consultants Inc.
Sun., Sept. 9, 2007
This article is part of PUBLIC WORKS magazine's live coverage from the 2007 APWA Show. Click here to read more articles from the show.