Environmental Engineering Reference
In-Depth Information
Figure B-30
The SKB site used only infiltration to preserve vegetation.
Three separate systems were designed as part of an overall site plan to capture
nearly all of the roof runoff from the new buildings, and most of the site runoff,
significantly reducing or eliminating the runoff going into the combined storm
and sanitary sewers during storm events (Figure B-31). A large gravel stormwater
storage and infiltration bed was placed under the school's turf athletic field to
retain water from the new building roof drains. A porous pavement playground
absorbs rainfall that falls directly on the surface (Figure B-32).
A rain garden captures roof runoff during storm events, filling a shallow
basin with gently sloping edges to a maximum depth of 15 in. Water in the rain
garden gradually infiltrates and disappears totally during dry periods, mimicking
ephemeral pools. A large wooden viewing platform makes it possible for teachers
to bring their classes outside, while boulders of natural stone allow individual
students to step among the cattails and experience the pond firsthand. This little
area provides habitat for a rich variety of insects, toads, birds, and other creatures
that inhabit ephemeral ponds, not found in the community.
Urban Stormwater Restoration for the Washington
National Cathedral (2001)
With the construction of the Washington National Cathedral at the top of a
wooded hill in Georgetown, DC, the amount of runoff generated from the site
was greatly increased (Figure B-33). Stormwater runoff was piped and concen-
trated into a ravine in the historic Olmstead Woods, causing severe erosion. By
concentrating the flow, the soil mantle was denied sufficient water to keep the
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