Hi, We are trying to pursue both storm water quality control and quantity control credits. When we calculate the 2 year - 24 hour design storm it comes to about 6.75 inches and 25% of that we are going catch in a catchment area.
Then there will be an overflow from the catchment area and that we intend to release through a silt trap.
The confusing part is that we are in the wet zone and the quality control credit requires us to design the silt trap for 1 inch rainfall per 24 hours. But from the catchment area there will be overflow in the range of 75% of 6.75 inch 2 year - 24 hour design storm. That is about 5 inches and only 1 inch of that will be handled effectively by the silt trap. If we try to make the silt trap to handle a 5 inch storm then it becomes so large.
Am I making the correct reasoning here? Or how should I handle this situation? Please advise. Thank you.
Michael DeVuono
Regional Stormwater LeaderArcadis North America
LEEDuser Expert
186 thumbs up
June 7, 2013 - 7:40 am
Are you sure about the 6.75 inch depth? That is a 50-year storm depth here in the Mid-Atlantic.
Magda Aghababyan
CEOCo-Energi (Pvt) Ltd.
15 thumbs up
June 11, 2013 - 12:11 am
Thank you Michael for the reply. This project is in SL and usually we get quite heavy rain all through the year. So given that this 6.75 inch is correct, am I reasoning this in the correct direction?
Michael DeVuono
Regional Stormwater LeaderArcadis North America
LEEDuser Expert
186 thumbs up
June 11, 2013 - 10:29 am
That is a lot of rain.
Let me see if I understand this correctly. You are using the same BMP to manage both peak rate and volume (6.1), and water quality (6.2). The 6.75" depth is the controlling factor, and is producing a BMP which is much larger than that which would be required if you were simply going after 6.2???
In short, to answer your question to the best of my ability (again, I am not sure I understand this correctly), if you are going to use the same facility to meet both 6.1 and 6.2, you need to size this accordingly, i.e. based on the 6.75" depth, and the requirements of 6.1, then 6.2 should simply fall into place.
Let me know if this helps, or if I completely missed the mark on this. I wish we could upload images here, it would sure make my life easier!