Our project site is a University Campus in North Carolina. Part of the LEED boundary site area includes a natural forested and grassy area which we are not disturbing as part of the project. For the LEED quality point we need to capture and treat 90% of the runoff from the annual average rainfall (1" for our site-humid area) within the LEED boundary area. The SCS soil survey lists the soil type on site to be Hiwassee Loam, hydrologic soil group B. The SCS curve number for grassed pervious areas would be 61. According to Table 2.1 (runoff depth table) in SCS TR-55 (Urban Hydrology for Small Watersheds ) a 1" rainfall depth produces no runoff for curve numbers below 70. Since no runoff will be produced in this area for the 1" rainfall event, how do we show in this in LEED quality point worksheet? Show it as a non-structural BMP infiltration area?
The project is seeking clarification for how stormwater infiltrated on-site should be documented for certification. Per the LEED Reference Guide, water that is infiltrated on-site is assumed to be 100% treated for the purpose of this credit and is considered to be a non-structural control. Therefore, the Non-Structural Controls section of the Submittal Template should be completed, stating the percentage of stormwater that will be infiltrated in this area. Applicable Internationally.