USGBC Rating System

LEED-NC 2.2 lists the Intent, Requirements, and Potential Technologies and Strategies for this credit as follows:

Intent

Limit disruption of natural hydrology by reducing impervious cover, increasing on-site infiltration; and managing stormwater runoff.

Requirements

OPTION 1 EXISTING IMPERVIOUSNESS IS LESS THAN OR EQUAL TO 50%

Implement a stormwater management plan that prevents the post-development peak discharge rate and quantity from exceeding the pre-development peak discharge rate and quantity for the one- and two-year, 24-hour design storms.

OR

Implement a stormwater management plan that protects receiving stream channels from excessive erosion by implementing a stream channel protection strategy and quantity control strategies.

OR

OPTION 2 EXISTING IMPERVIOUSNESS IS GREATER THAN 50%

Implement a stormwater management plan that results in a 25% decrease in the volume of stormwater runoff from the two-year, 24-hour design storm.

Potential Technologies and Strategies

Design the project site to maintain natural stormwater flows by promoting infiltration. Specify vegetated roofs, pervious paving, and other measures to minimize impervious surfaces. Reuse stormwater volumes generated for non-potable uses such as landscape irrigation, toilet and urinal flushing and custodial uses.

Calculations and Considerations

To understand this credit and determine potential technologies and strategies, the first thing that needs to be understood is what the term imperviousness means. Ordinarily in land development and watershed analyses, the features on the land may be divided into two characteristic types of surfaces: pervious or impervious surfaces. Impervious surfaces are...