Stormwater management has a lot of benefits, some of which are very obvious and other are long-term, save the planet types of goals, but all worthy of note. The first goal of managing stormwater is to keep it from flooding homes, eroding topsoil, and causing damage. That has been the major goal of managing stormwater for hundreds of years, protect assets, save the valuable soil. Now, however, there are two more, very important goals. One is to help retain the water to replenish the aquifers and the other is to filter out all garbage and contaminants before the water reaches a stream or river. Now there are advanced stormwater filtration systems in place in many cities and more being retrofitted all the time. Here is how they work.
The Standard Goal Of Stormwater Detention
When it comes to stormwater, the main goal nowadays is to mitigate the increase in water flow that is caused by development. The standard development usually causes an increase in runoff and volume from stormwater about 2.8 times higher than historic flows before any type of developments.
The primary goal is to return the watershed to its previous retention level pre-development. While this sounds admirable, it’s nearly impossible, but with proper detention and retention of stormwater flows it can be nearly attained.
As Important Is The Stormwater Filtration System
One of the biggest problems with the stormwater management systems is that, when the rain falls hard, lots of garbage and pollutants are rushed into the drainage system and overwhelm natural streams and rivers. In an effort to lessen the effects of all those chemicals, pollutants, and garbage, there are special filters installed in various sites along the way.
The first effort will always be grating and sieves on the street level that are designed to capture plastic bottles, bags, and food containers. These can then be swept up by street cleaning machines or picked up by hand.
The next step occurs below ground level where there are hydrodynamic separators under the surface of the road. These use the natural swirling property of water to help jettison some kinds of floatables into retaining areas while heavier sediments accumulate in the bottom of the swirl. There are no moving parts in these hydrodynamic separators, only the swirling action of the water is used to do the sorting.
During the dry days, large vacuum trucks can then make a route to each of the separators and vacuum out all of the debris, garbage, and sediments. Most of these hydrodynamic separators have a goal to eliminate up to 80-90% of the various different types of garbage and pollutants. By stopping them from entering the main stormwater system it eliminates the problem of trying to catch them farther down the system.
Once many of these pollutants reach a river or stream, it’s too late to stop the damage that they are going to cause. It’s always better to have several different filtering mechanisms along the route, each with a goal of removing one type or another of pollutant. Then by the time the water reaches the stream it has been mainly cleared and won’t be causing fish kills on rainy days.