Combined sewage overflow (CSO) is caused by excess storm water flooding our sewers; because of the flooding, effluent (including waste water and industrial pollutants) pours straight into the receiving waters, untreated. While heavy rain and melting snow are the typical cause of CSO, buried streams also contribute to the overflows.
Buried streams, typically found in urban areas, are bodies of water that have been directed into pipes or buried beneath buildings, construction zones, and other quintessential parts of an urban landscape. Usually forgotten about fairly quickly, buried streams make their presence known when, instead of pooling at the surface of the land, they flow into storms drains, or underground directly to the local sewer system. There, they add millions of gallons of water to the already overwhelming amount that must be treated. The excess water brought by these buried streams contribute to the CSO problem New York City faces. Buried streams can also cause home flooding when, during heavy rains, they flood directly beneath basements and cellars.
Over the past few decades, many attempts – some more successful than others – have been made to “daylight” (deliberate exposure of) these buried streams.
Benefits of daylighting:
- Reduce amount of storm water flowing into storm system, both lightening the load put on waste water treatment systems and leading to a reduction in CSO
- Improve water quality through the growth of aquatic vegetation that uptake pollutant
- Reduce erosion
- Reduce flooding
- Improve the local ecosystem and create new habitats
- Creation of an educational site for school children and college students
- Improvement of local parks
Challenges of daylighting:
- Stream sources must be located and excavated
- The original channel in which the stream flowed must be found
- Streams and their original channels may be located beneath homes, buildings, landmarks, buried utilities or other structures that cannot be easily reconstructed to accommodate the new water framework
- The cost of excavating streams may be too high for municipalities to justify to taxpayers
- Ownerships of the stream may be disputed
- Landowners near the daylighted stream may be subject to additional environmental regulation
- Streams, if neglected, can collect trash or promote the growth of disease-carrying pests like rodents and mosquitoes
All references last accessed April 10, 2010
Image 1: http://www.conservation-ontario.on.ca/source_protection/files/watershed_labeled_hor.jpg
Dearen, J. “Plans percolate to revive some SF native creeks,” Yahoo News, 2010. Web. http://news.yahoo.com/s/ap/20100424/ap_on_re_us/us_revived_urban_creeks
Elmore, A.J., and Kaushal, S. S., “Disappearing headwaters: patterns of stream burial due to urbanization,” The Ecological Society of America. Web-PDF.
“Daylighting,” Minnesota Sustainable Communities Network, 2009. Web. http://www.nextstep.state.mn.us/res_detail.cfm?id=356
Pinkham, R. “Daylighting: New Life for Buried Streams,” Rocky Mountain Institute, 2000. Web. http://www.rmi.org/rmi/Library/W00-32_DaylightingNewLifeBuriedStreams
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