In a properly designed stormwater system, the catch basin is the first point of entry for stormwater draining from a site. The catch basin, the grate you see on the top of the pavement and the concrete box below the surface, traps the water while the pollutants, most of which are heavier than water, settle out of the stormwater to the bottom of the catch basin – the sump area.
It is the catch basins which are both the hardest working part of the storm system and also the best place to spend the majority of your stormwater maintenance effort. Why? Because the catch basin is the workhorse of the overall system.
As the entry point for stormwater, the catch basin is in a position to catch the majority of the pollutants before sending the stormwater downstream to the next storm system feature. If the system is properly designed, the catch basin will precede the more substantial features such as manholes, filters, vaults, etc. As such, the catch basin is always in the position to catch pollutants. The question then becomes is it in a condition to catch pollutants.
The catch basin has 3 basic parts – the grate, the pipe connections, and the sump. The grate is for letting stormwater into the system and the pipes are for routing the stormwater through the system. The sump, the area of the catch basin below the pipe penetrations down to the bottom of the catch basin, is there for the sole purpose of catching and storing pollutants until they are removed (OK – energy dissipation, too, but that’s another blog post). If the sediments are not removed often, then the very pollutants being stored there waiting for their removal become the major source of downstream pollution because they are stirred back up by the moving stormwater and washed downstream. When they go downstream, they have the ability to pollute and foul the more sensitive, expensive systems such as stormwater filters, vaults, or manholes. Ultimately, those pollutants foul the rivers, streams, and bays.
Keeping those catch basins clean, then, becomes the major task of stormwater maintenance. How often should you clean them? Good question. The answer is as often as you can. A recent study found that the more they are cleaned the cleaner the overall system stays. Doing so keeps the downstream system cleaner longer. That is not only good for the environment – it is good for your checking account.
– See more at: http://www.catchallenvironmental.com/blog/the-catch-basin-the-key-to-effective-stormwater-maintenance#sthash.gHtejLhj.dpuf