Page 89 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

70 Cha pte r T w o

Case 2 Exemplary Performance One exemplary performance point may be earned on
most sites if
OS ≥ 2BF and is contiguous to it (2.5.13)

or, on urban sites where SSc2 is also earned,
OS + VR + PED25LS ≥ 2BF (2.5.14)

Case 3 Exemplary Performance One exemplary performance point may be earned on
most sites if

OS ≥ 0.4A (2.5.15)
T
or, on urban sites where SSc2 is also earned,
OS + VR + PED25LS ≥ 0.4A (2.5.16)
T

2.6 SS Credit Subcategory 6: Stormwater Management

SS Credit 6.1: Stormwater Management—Quantity Control

USGBC Rating System
SSc6.1 is worth one point in LEED 2009 and was worth one point in LEED 2.2. LEED-
NC 2.2 lists the Intent, Requirements, and Potential Technologies and Strategies for this
credit as follows, with modifications as noted for LEED 2009 and redesignated as cases
and then options:
Intent
Limit disruption of natural hydrology by reducing impervious cover, increasing on-site
infiltration, and managing stormwater runoff.
Requirements
LEED 2009 CASE 1—EXISTING IMPERVIOUSNESS IS LESS THAN OR EQUAL TO 50%
LEED 2009 Option 1: 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
LEED 2009 Option 2: Implement a stormwater management plan that protects receiving
stream channels from excessive erosion by implementing a stream channel protection
strategy and quantity control strategies.
LEED 2009 CASE 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.