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Exterior Water
Management
Sustainable site
development can help solve regional
watershed problems at the source. Good site
design and water management practices
address water management issues by:
- Increasing the
permeability of constructed pavements
- Capturing and
treating excess runoff by means of
natural soil and biological processes
- Minimizing or
eliminating potable water usage in the
landscape
- Maintaining or
restoring the infiltrating, cleansing,
and storing functions of soils, plants,
and groundwater with natural landscape
systems.
Stormwater is
precipitation that does not soak into the
ground or evaporate but flows along the
surface of the ground as runoff.
Conventional practice for storm water
management—concentrating runoff and carrying
it off a site as quickly as possible through
storm sewers—causes various environmental
problems, including erosion and downstream
flooding, pollution loading of surface
waters, and reduced ground water management recharge.
There are two basic
principles to storm water management:
(1) Drainage and flood control is based on
managing the quantity of stormwater runoff
potentially generated during a design-basis
storm event (a storm event likely to occur
only once in a specified time period). The
major contributors to stormwater runoff are
impervious surfaces such as rooftops and
parking lots.
(2) Water
management quality
control is based on managing the on-site
sources of pollutants in stormwater and, if
needed, treating these pollutants.
Pollutants entering stormwater are primarily
caused by erosion of soil (creating sediment
pollution) or contacting surfaces that have
accumulated pollutants since the last storm
event. Rooftop surfaces typically accumulate
pollutants that are deposited from the
atmosphere or blown on during adverse
weather, while parking lot surfaces collect
a variety of pollutants leaked from
vehicles.
The primary goal of
sustainable storm water management is to
generate no additional runoff from the
existing site as compared to undeveloped
conditions. The intent of this design goal
is to utilize an integrated approach that
minimizes the generation of stormwater
runoff and promotes infiltration of the
generated stormwater into the subsurface.
This approach limits runoff (and potential
pollutants) from leaving the site. An
integrated design approach involves
configuring the location and placement of
impervious surfaces, specifying land-based
structural practices (stormwater storage and
treatment) for stormwater pollution control,
and integrating native landscaping into the
overall site development.
Investigate the
feasibility of applying storm water management
strategies to treat and retain stormwater on
the site. Each of these strategies requires
specific maintenance practices for proper
operation.
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