Managing
stormwater runoff with detention ponds is like trying to lose
weight by taking diet pills: long-term consequences outweigh
short-term benefits. Natural systems such as wetlands do the
job better, more beautifully, and more responsibly.
By Deborah Snoonian, P.E.
A dense cover of plant growth is necessary for removing pollutants.
Native plants are preferred, but research seems to indicate
that controlling the growing conditions, rather than the specific
plant species, is the most important criterion of success. Conditions
are most fragile when a wetland is first installed, as seeds
germinate and plants first establish themselves. Planting seeds
or vegetation correctly can be challenging for traditional “mow,
blow, and go” landscapers who usually plant large lawns.
Andrea Kendall, an environmental specialist with Beals and Thomas,
of Southborough, Mass., recalls her experience with one contractor
in the Northeast: “After the wetland was installed, we
had to go back to the job site because the cattails were floating
on the water surface. They hadn’t been planted correctly.”
Those who design wetlands admit that finding qualified landscapers
to do site work can be difficult, but they believe service will
improve as the systems become more popular.
Natural vegetation also behaves differently from the grass
and ornamental plantings of conventional landscaping. “Unlike
lawns, which are monocultures that can be irrigated and fertilized
to grow uniformly, you can’t expect a variety of native
plants to propagate at the same rate,” explains Matthew
Urbanski, a principal with landscape architecture firm Michael
Van Valkenburgh Associates in New York. “There’s
a bit of a ratty period when things are growing in.”
Ratty periods may be anathema to owners, so when appropriate,
architects should work with other team members to accommodate
this concern. Often, altering the construction schedule so
that landscaping and site elements are completed earlier than
usual allows enough time for vegetation to establish itself.
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Case Study
EMC Corporation, Hopkington,
Mass.
Company: Beals
and Thomas, Inc., Southborough, Mass.
A constructed wetland was built at this research
and development facility to treat runoff and control
flooding for seven and a half acres of paved surfaces.
Runoff first enters a catch basin (not shown here)
to slow its velocity and remove some sediment, as
well as oils and grease, that floats on the water
surface. As it enters the wetland system, the water
is further treated by wetland vegetation. “We
wanted to pretreat the water so it wouldn’t overburden
the constructed wetland system during large storms,”
said Andrea Kendall, an environmental specialist with
Beals and Thomas. Her firm completed all the site
work for the project.
Following construction, the second phase of the project
involves monitoring water quality to ensure compliance
with EMC’s discharge permit.
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The ways of the wise
Natural runoff management techniques look all the more attractive
considering the current regulatory environment (see “Regulations
for Runoff and Wetlands,” page 134). “Local governments
and communities are much more environmentally savvy than ever
before,” says Wendi Goldsmith, a landscape designer and
president of the Bioengineering Group in Salem, Mass. “Using
wetlands can be a way for developers to endear themselves
to citizens who review their proposals.” It can also
be a way for architects to endear themselves to clients—Goldsmith
notes that the process often goes more quickly when natural
treatment systems are part of the overall plan.
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