Hopefully you are all aware that your regular sediment control pond relies on time and very slow water velocity to drop the particles out of suspension to the bottom. If you were to look at your soils on site, you would notice that the particle size as compared to the volume and retention time of your average sediment control pond just doesn't cut it - not even close.So why even dig them in the first place? The simple answer to that, is because that's all people know how to do. Repeat past mistakes.
If you insist on digging a sediment control pond (detention pond) on your next site, then you'll need to upgrade it to a Rolls-Royce. The Rolls-Royce of sediemnt control ponds. And here's how in a few 'easy' steps:
1) Line the pond edges with poly sheeting or filter fabric (geotextile) - leaving no exposed soil;
2) Install berms in the sediment pond almost to the height of the pond itself (allowing only a foot or so in case the water fills behind, then overflos into the next chamber);
3) Retain the water behind each berm for as long as possible, forcing the water to flow through each berm, or crest over the top;
4) To accomplish #3, put a nice thick layer of washed sand on the 'upstream' side of each berm - this will provide two functions: hold the water back, and filter out some finer sediment (to completely filter out fine silts and clays, many sand stages are necessary);
5) Install sand-core-berms: if the water must pass through the berm, why not have a sand core to help filter water as well? You will need to wrap the sand in geotextile and then cover with heavy rock to stabilize it all; and finally
6) Think about playing with the elevations of your chambers in the sediment pond: the first chamber should be nice and deep, then maybe have the second chamber very shallow so water skims across the surface covered with sand or vegetation (if available), and then into another deep chamber after passing over a floc bag, etc.
Alas, the sediment pond requires thinking and experimentation to take it to the next step. So if you're going to install one on your next site, try one or all of the above ideas to help your pond perform better and impress your client.
