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Wednesday, May 6, 2009

Threats to an Orange County River Parkway

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Will a Pristine Canyon in South Orange County be Modified to Clean up Urban Runoff Pollution from Upstream Developments?



http://www.lagunagreenbelt.org/page15/page15.html

24 small dams proposed in Aliso canyon park in OC


http://www.lagunagreenbelt.org/page1/page4/alisocreek.html

1. The SUPER project doesn't address the volume and water quality of runoff from up-stream cities. It just allows the impact of those excessive and polluted flows to impact the "wilderness" park. The natural flow patterns of the stream are being sacrificed to this out-of-control run-off.
2. The plan involves leaving in place the existing concrete dam that has caused much of the present erosion problem.
3. There is a series of check dams which are described to be only 2' tall, but the foundation for these is designed to go all the way to bedrock. Since this is a deep alluvial valley, that could be 20' down or more. If erosion occurs below and around these dams, the full height of these dams could be exposed. Also with a big flood, the dams could fail and end up on the beach in pieces after destroying vegetation and improvements
along the way.
4. The plan includes constraining the creek between reinforced banks on both sides. This is channelization, but the project proponents don't use these words. So the stream will no longer meander, and horseshoe bend will never be restored.
5. Water quality is only addressed at the mouth of the creek with a UV treatment system. It should be addressed before run-off enters the stream, at the outlets (Aliso Viejo has installed a prototype), and all along the stream by allowing the stream to flow the longest possible distance through wetlands vegetation.

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