Main Trail Head 4
Greenhill Avenue or Rosehill Park
Watershed System of the Red Hill Valley
The Red Hill Valley watershed is part of a larger ecosystem, a living machine. The cycles of nature are such that life comes and goes within that ecosystem. As the season changes, the look of the landscape changes. The bright colors of fall symbolize a great celestial bear hunt to the original people. As hunters chase a wounded bear across the sky, blood from its wound falls to earth and changes the colors of the leaves. At night time you can see the hunters and the bear in the shape of the Big Dipper. When it is overhead, autumn has arrived. If you are here in spring, then a great time of renewal is a taking place as the plants are emerging from the earth, birds are returning to the Valley and animals birth their young. Fish also return to spawn. The earth slowly warms so that humans can plant their crops. If all conditions are right, a great harvest can be enjoyed in the fall.
Here at the Greenhill flood control site, a low flow channel carries day-to-day water along with small storms and the sediment in the water without any ponding. During bigger storms the “sediment-moving-stream” breaches its banks by using the new expressway embankment as a dam. This reduces the rate of flood that flows downstream and protects the road from flooding.
In the early twentieth century accepted practice had municipal storm and sanitary sewers combined carrying wastes to the sewage treatment plant. During storms, strategically placed relief points called overflows discharged sanitary sewage and stormwater directly to our creek and lakes. The impact of the sewage was diluted by the storm runoff. Over time we have become increasingly aware of the environmental damage of these combined sewer overflows (CSO). The innovative solution used here in the Red Hill Valley collects excess combined sewage in tanks to prevent it from discharging into the creek in all but the worst storms and sends it to the sewage treatment plant after the storm. This solution, while costly to build and maintain, is still more economical than physically separating the sewer network. The Greenhill CSO-2 tanks serving…homes reducing overflows from 25 per year to 2 per year. The rainfall which used to discharge upstream of this point has been extended under the new channel to its new location.