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Storm water overflow


...continued from page 5

The retention basin runs underground from the area near 12 Mile Road and Stephenson Highway to Dequindre Road, just north of 13 Mile Road.

"That took us down to about 12 or 15 discharges a year, and it stayed that way for about 30 years," Nigro said. "The idea is continual growth. In 2003 or 2004, we added another 30 million gallons of storage, and a big screening facility. We improved the chlorination system to make it more efficient. We are down to about eight or nine discharges a year, so the quality keeps getting better. The MDEQ recently came to us and wants us to cut that number in half, again. I'm not sure what improvements we can make to the facility without a $100-million price tag."

"The GWK is one of the most impressive facilities of its kind in North America," Oakland County Water Resources Commissioner Jim Nash said. "I'm extremely proud of the extraordinary progress GWK has made over the years in reducing combined sewage overflows and maintaining the highest water quality standards possible."

Nigro said further reducing overflows may be done by implementing "green infrastructure," rather than building a larger basin. The approach means using more porous pavements that can capture water and allow it to flow through the pavement, rather than allowing it to run off, and other improvements that reduce the amount of water entering the system.

The state of Michigan took a large step forward in 1988 when it initiated a CSO control program, while in 1994, the federal government developed a nationwide CSO control policy. The policy suggests that states use an enforceable mechanism, preferably a permit program that was initiated by the federal Clean Water Act, called the National Pollutant Discharge Elimination System, which required communities to implement new measures to control CSOs.

The program included developing long-term control plans using nine minimum controls, according to the MDEQ. Those controls basically included interim measures that could be taken to begin addressing the CSOs before major sewer system construction activities would be undertaken. In Michigan, all municipalities with CSOs have completed the required measures and developed long term control plans.

The long term control plans must assess a range of control options, including costs and benefits, and lead to selection of an alternative that would meet federal and state clean water laws. Since the cause of CSOs is an excess of rain or snowmelt, some municipalities have decided to separate their combined sewers, thereby redirecting the clean water runoff to lakes, rivers and streams via storm sewers. However, storm sewer separation projects are expensive, and often involve extensive utility and road reconstructions.

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Tags: LONGFORM

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