For this project, the proposed condition reduces the existing impervious area by 38% below the existing condition, therefore the project received a waiver for storm water management, quantity control. Stormwater management requirements were met by reducing the existing impervious area on site. The "2000 Maryland Stormwater Management Design Manual" requires a reduction on 20% of existing impervious to meet stormwater management requirements and, in this project, an impervious area reduction of 38% was achieved. If by reducing the existing impervious area by 38%, does our project meet the requirement of the credit?
No, the proposal to reduce the impervious area below the existing condition does not fully meet the intent of LEED SS credit 6.2. The intent of SS credit 6.2 is to reduce water pollution by reducing impervious cover, increasing onsite infiltration, eliminating sources of contaminants, and removing pollution from stormwater runoff. While the 38% reduction of impervious cover may qualify for SS credit 6.1 (see Option 2), the runoff from 90% of the average annual rainfall over the remaining impervious cover must be treated using acceptable best management practices like those found in the 2000 Maryland Stormwater Design Manual. Reduction of impervious area as the sole justification for the credit is not acceptable. Note: Reduction of imperviousness by itself does not meet the stormwater management requirements found within The 2000 Maryland Stormwater Design Manual. However, reducing impervious coverage will reduce the required treatment volumes. Applicable Internationally.