Section 2: Individual LEED Credit Reviews
LEED Credit SS-6.2:
the landscape-based Best Management Practices
may be feasible to treat a portion of the site's
Stormwater Management
stormwater runoff.
Treatment
Another approach to achieving the credit is the use
of subsurface water quality inlets with sand filters.
Depending on the filter design and the
contaminant concentrations of the influent, sand
Intent
filters can reduce both TSS and TP at rates at or
Limit disruption of natural water flows by
above those defined in the credit criteria.
eliminating stormwater runoff, increasing on-site
The U.S. Green Building Council has also
infiltration, and eliminating contaminants.
determined that the phosphorous reduction
requirement of this credit can be achieved through
Requirement
a "source reduction" approach that involves
Construct site stormwater treatment systems
minimized fertilization of landscape plantings, low-
designed to remove 80% of the average annual
or no-phosphate cleaning agents, and similar
post-development total suspended solids (TSS)
strategies. These measures need to be specified in a
and 40% of the average annual post-
building/landscape maintenance plan. If this
development total phosphorous (TP) based on
approach is used, it may be feasible to meet the
the average annual loadings from all storms less
TSS criteria through other types of water quality
than or equal to the 2-year/24-hour storm. Do
inlets (besides sand filters).
so by implementing Best Management Practices
The use of porous pavement can also contribute to
(BMPs) outlined in Chapter 4, Part 2 (Urban
this credit if used for some walkways or light duty
Runoff), of the United States Environmental
vehicular access drives.
Protection Agency's (EPA's) Guidance Specifying
Management Measures for Sources of Nonpoint Pollution
Basis for Cost Assumption
in Coastal Waters, January 1993 (Document No.
EPA-840-B-92-002) or the local government's
BMP document (whichever is more stringent).
For the purposes of this study, Credit SS-6.2 was
pursued only in the Courthouse model--the scope
(1 point)
of the Office building modernization does not
include site work.
Cost Impact = 4
For the Courthouse, a subsurface sand filter system
has been included. The system is sized to treat a
two-acre impervious area and includes costs for
1
2
3
4
5
connections, excavation, and backfill.
Because this type of system has attended
GSA
No
Low
Moderate
High
Mandate
premium,
premium
premium
premium
maintenance costs and is not typically required for
(50-150K)
(>150K)
(no cost)
psble svgs
(<50K)
GSA projects, it has only been included in one of
the Gold rating scenarios.
Practical Applications
As the majority of GSA's projects are developed
on urban sites with limited amounts of open space,
many of the landscape-basd Best Management
Practices (e.g., infiltration basins, vegetated filter
strips, constructed wetlands, ponds) will have
limited applicability. Exceptions may include new
Courthouse projects, where security-driven setback
requirements result in relatively large site areas
surrounding the buildings. In these cases, some of
GSA LEED COST STUDY
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