LEEDS Credit No. 6.2 1

[bank]

LEEDS Credit No. 6.2 gives one point for storm water quality on a project seeking LEEDS certification. One requirement is that the design must capture and treat 90% of the annual rainfall. Most storm water quality management units on the market are designed to treat the first flush only, with the excess bypassing the unit and going directly to the outfall. The idea is that the majority of pollutants are in the first flush, and if a unit can remove 90%+ of pollutants from the first flush it has essentially cleaned the storm water to an acceptable level.

My questioning is, would that line of thinking be acceptable to the LEEDS gurus? If the first flush amounts to 10% of the total rainfall, but contains all of the pollutants, if you remove 90% of those pollutants would that qualify you for the LEEDS point (assuming the other requirements are met)?

 

[bpattengale]

We've run into this before on our LEEDS certification. If you read the credit it gives the total rainfall ammount per storm that needs to be treated for the practice to be assumed to treat 90% of the total yearly rainfall. If I remember correctly (The last LEEDS project I did was about a year ago) there are three areas the country is broken into, they're like semi-arid, semi-wet something like that. The actual rainfall ammounts needed to be treated for our area (Minnesota) was 0.90" total rainfall, I think.

Most of BMP/Storm water quality management units are capable of treating the peak runoff rates from a 1" rainfall event without bypassing the flow.

Read through the credit again to find the storm rainfall total that the BMP needs to treat and then do the runoff calcs to show that the BMP does not bypass for that event.

You should be able to claim the credit then.