We're trying to show compliance with SSc6.1. On the form they ask for Pre-development and Post-development runoff rates and quantities. The credit requires "Case 2. Existing imperviousness is greater than 50% and a stormwater management plan will be implemented that results in a 25% decrease in the volume of stormwater runoff from the two-year, 24-hour design storm." With"25% decrease in VOLUME" being the key phrase for us.
Our Pre-development Rate is 0.234 CFS and Quantity is 2,022 CF
Our Post-development Rate is 0.2754 CFS and Quantity is 0 CF
Notice that the Rate is higher but we will now have ZERO runoff (Quantity is lower) because all runoff will be/is infiltrated on-site. Since the form is not recognizing this and allowing us the point, should we try and go with:
"Special circumstances preclude documentation of credit compliance with the submittal requirements outlined in this form."
OR
"The project team is using an alternative compliance approach in lieu of standard submittal paths."
Thoughts? Recommendations?
Gregory Hurst
Office ManagerRobert Peccia & Associates
66 thumbs up
October 13, 2010 - 12:42 pm
My inital thought is that you are infiltrating the entire volume within your LEED boundary (I assume) and if this is the case, then your run-off flow rate is also zero. You only need to measure the rate and volume as it leaves your site.
Caroline O'Leary
Architectstudio point253
99 thumbs up
October 13, 2010 - 12:59 pm
Gregory,
Thank you for the response. That was what we decided to do until we heard opinions otherwise. Our Post-development Rate and Quantity are now set to zero. The form allowed this and allowed us the point.