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Doing it the natural way: A
wetlands expert spells out the benefits
Can you design a runoff treatment system using Mother
Nature’s ingenuity? The answer is yes—specialized
consultants provide these services. record asked Wendi
Goldsmith, a certified stormwater quality specialist
and president of the Bioengineering Group in Salem,
Mass., to explain how it’s done and why it’s
important. Goldsmith’s firm designs natural runoff-management
solutions and provides technical and policy guidance
to the EPA on a variety of stormwater issues.
Trained as a geologist, soil scientist, and landscape
designer, Goldsmith has an unerring grasp of wetland
and watershed science, and she’s an avid proponent
of making developed sites operate as ecosystems. “A
landscape isn’t just a pretty place,” she
says. “It has forms and functions that make it
work a certain way to control flooding naturally and
rid water of pollutants. When we pave over the landscape,
it loses these functions. Where water goes and doesn’t
go, what it comes into contact with as it flows, how
long it takes to move from a pipe to a natural body
of water—all these have an effect on water quality.”
If landscapes were allowed to work the way nature intended,
she says, we’d have no need for storm sewers or
detention ponds.
Using land treatment is a relatively new concept in
the U.S. Before the 1960s, stormwater management meant
draining city streets as quickly as possible to prevent
flooding, and channeling the runoff to the nearest body
of water. The result was ever-larger networks of storm
sewers, as urbanization increased to accommodate population
growth. When building these networks became too expensive,
engineers began using detention ponds to hold runoff
before letting it drain to waterways. “We spent
a lot of money building and now maintaining a system
for water management which Mother Nature was taking
care of beforehand,” Goldsmith says. Finally, in
the 1970s, the scientific community recognized that
not only were these practices only marginally effective
in preventing flooding, they were also causing significant
environmental damage. With the EPA’s enactment
of the Phase II stormwater rules in December 1999, the
problem has garnered an unprecedented level of national
attention. The Phase II laws require virtually all developed
sites to manage runoff more responsibly. “Every
architect and builder needs to have at least a rudimentary
understanding of stormwater issues now,” she notes.
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Runoff management should focus on reducing flow and
creating landscapes whose hydrology mimics that of natural
systems. This means roughly 50 percent of precipitation
leaves the site through evapotranspiration (a combination
of evaporation and respiration through the leaves of
plants), and about 45 percent seeps through soil into
groundwater, with no more than 5 percent leaving as
runoff. Sustainable watershed hydrology happens naturally
in forested and vegetated lands, which Goldsmith calls
“multifunctional, self-maintaining, solar-operated
water quality treatment systems.”
When a constructed wetland is part of a site plan,
design parameters such as size and depth are determined
based on the site characteristics (area drained, soil
type, amount of paved versus unpaved surfaces) and based
on the volume of runoff expected in certain weather
conditions. But they aren’t the sole solution to
every runoff problem. Nor do sites have to be entirely
covered with vegetation to operate as healthy ecosystems.
Goldsmith is a pragmatist. She acknowledges that development
will happen, that conventional paving materials and
construction methods aren’t going away any time
soon, and she’s quick to point out the variety
of techniques that can be used to achieve the right
balance. “The best way to manage runoff is to use
every square foot of a site wisely,” she says.
“Green roofs [roofs planted with vegetation] are
an excellent way to capture and hold runoff from a rooftop.
Porous pavements allow parking lot runoff to percolate
through the soil. Water can be captured in underground
filtration beds and allowed to trickle back into the
ground, or caught in roof cisterns and used for on-site
irrigation.”
Balance is the operative principle here; unfortunately,
urbanization has tipped the scales toward one-dimensional,
engineered quick fixes. Goldsmith, whose passion to
protect watersheds is clearly articulated in both her
words and her firm’s work, is glad that regulations
and a general heightened awareness of environmental
issues is turning the tide against the status quo. “The
minute you let water enter a piping system,” she
muses, “you’ve basically lost the opportunity
to treat it.” DS
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