Pre Development Determination

Hi, I deal with this all the time with infill jobs in our city. The building is gone, but the basement floor is still there. For 6.1, quantity control, you would not model this as impervious, you are modelling the runoff. Just go by surface condition. The basement would come into play in 6.2. Quantity control.

I apolologize. I deal with so many different regs on a daily basis, I got confused. Thank you for your follow up question. Water quality is typically associated with volume control, this the reason for my confusion. The basement would come into play on any water quality BMP that uses infiltration. You don't have infiltration (unless you excavate the basement, I've done this before). I forgot that 6.1 deals with volume control as well. Again I apologize. You may or may not get this approved, but I have done raingardens on this exact type of site. You take a volume credit for the raingarden, the idea is that the volume will be lost due to evapotranspiration and some infiltration. I do not know the particulars on NYC regs though. Of course there is always capture and reuse, soil amendments,and landscape restoration and many other techniques to solve for volume. Without getting into specifics it is hard for me to add anything further. Frankly, most of the SWM regs required by a local municipality meet or exceed LEED standards. Especially if you need an NPDES permit I am not in NYC, I'm in Philadelphia. I'm typing this on my phone, so I do apologize for any typos, I hope this helps.