003 First Flush

First Flush — How to prevent this dirtiest water flushing off into the pond is the key feature to maintain clean water of the pond. Because of Highway 101, a parking lot of shopping mall, and a basin like topography of Marin city, all gray water run-off into the pond.

Especially, the first rain of the year flushs out all dust/dirt from all the street surface into the pond. This is called “First Flush” and the most contaminated gray water.

Building swale lines next to Highway 101 and the west side of the pond would prevent gray water runoff from Highway and a parking lot. All corrected gray water through swale lines would be drained by pipe line using by a pump force direct into the bay.

Also, the new cluvert placed 1m under the existing cluvert would enhance more fluent water exchange between the pond and the bay(brackish water).