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PROJECT ORIGIN: The
initial request was to create an exhibit area in the lobby
to explain how wetlands work and why they are important to
our environment. As this project developed, the scope
became much more significant. The plan proposed by
SMCO management was to create a wetland diorama in the
office lobby. In addition to an aquarium, we would include
diagrams of how a wetland functions, pictures of flora and
fauna that live in Michigan wetlands, and why wetlands are
critical habitats to protect. In addition, the landscape
outside would be updated to help draw visitors to the lobby
entrance.
CONCEPT EVOLUTION: After
some discussion with the SMCO design team, I suggested
creating something more significant: rather than create a
wetlands display, why don’t we build a working wetland? The
“gumdrop and meatball” landscape in front of the office
needed to be replaced anyway. After a short discussion,
everyone realized that an actual wetland outside the lobby
would have significantly more impact on visitors than a
lobby display. It was decided that this would be a perfect
solution. Soon we had the approval to start the design
work.
My concept for this project was to
replace the existing landscape with an entire ecosystem.
This ecosystem would begin with a waste treatment wetland at
the west end of the building. After being treated and
cleaned in the wetland, the water would flow into a
meandering stream running the length of the building. The
stream would end in a pond containing fish, turtles, and
other aquatic life. The water would then be pumped from the
pond back to the waterfall at the west end for aeration. To
enhance the appearance of a wetland environment, a boardwalk
would be constructed along the edge of the landscape. The
design of this boardwalk would provide a number of
observation overlooks. The displays in the lobby would
provide additional information for visitors, completing this
educational landscape.
This design would allow for a very
diverse landscape, typical of a natural environment
containing both wetlands and uplands. Because this would be
a working system, regular water testing would provide a data
stream showing the effectiveness of this constructed wetland
in treating wastewater.
THE DESIGN BEGINS:
The first problem was getting sufficient width in front of
the building to create the meandering stream and landscape
we envisioned. To gain an additional seven feet of
landscape area, we decided to remove the existing concrete
sidewalk. A new boardwalk was built on top of the roadway
. This provided a pedestrian route for observing the new
landscape while leaving adequate space for vehicles.
Our desire for environmentally responsible design extended
to the selection of a tropical hardwood called IPE for the
construction of the boardwalk. IPE is naturally rot-
resistant, eliminating the need for chemical wood
preservatives. The lumber is harvested from environmentally
managed rain forests.
The next concern was the circulation of
water. The overall goal was to minimize the number of pumps
to simplify maintenance and keep electrical use low. There
are two circulation systems in this design. One moves the
wastewater from the sewer to the treatment area and the
other moves the water from the pond back to the waterfall.
Through careful planning of soil and water elevations, only
one pump was needed for each circulation system. When
the grinder pump cycles on, wastewater is pumped from the
sanitary sewer to the septic tank. The anaerobic phase of
sewage treatment and clarification begins at this point.
From there, it flows into the constructed wetland. This is
a sub-surface flow wetland, meaning that there is no open
water. The water flows laterally through a bed of gravel.
Plant roots grow down into the gravel, capturing the
nutrients and sediments present in the water. The wetland
plants also provide oxygen for the beneficial bacteria,
allowing them to break down contaminants present in the
water. The gravel bed is covered with peat moss, providing
insulation during the winter months.
Next, we wanted to make efficient use
the treated water. We felt that the best way to do this was
to use the water for irrigation. A conventional irrigation
system would have required sprinkler heads, pumps, and
pipe. This would also have been another system to
maintain. Instead, we used mother nature as our guide,
using the stream for our water source. The water moves from
the stream to the soil below the plant beds, providing an
unlimited supply to plant roots without saturating the soil
surface. To accomplish this, the liner for the system
extended under the entire landscape. All of the soils and
plants were installed on top of the liner. By grading the
soils down towards the edge of the water, we created
different water regimes. Marginal or wetland plants were
planted near or in the water. Plants requiring less water
were planted at higher elevations.
Plants for the constructed wetland had
to be carefully selected to optimize the absorption and
utilization of nutrients from the wastewater. They also
were responsible for supplying oxygen to the beneficial
bacteria in the gravel bed, allowing them to break down the
wastes present in the water. Because this ecosystem is
surrounded by buildings and pavement, we felt that it would
primarily attract birds and butterflies. We carefully
selected evergreen, deciduous, and perennial plants for the
landscape with this in mind.
RESULTS: This project far
exceeded the expectations of the owner. The effectiveness
of the water treatment has been monitored by the SMCO
environmental engineering department since the completion of
the project. When comparing levels of nitrogen, phosphorous,
and suspended solids in the discharge from the septic tank
to the discharge from the constructed wetland, all are
reduced by over 90%. As the plants have matured and the
ecosystem has become established, the removal of wastes from
the water has continually improved.
Prior to this project, people would
seldom even walk by the front of the building. Now there
are usually half a dozen employees enjoying the flora and
fauna at shift change and break times. To help with visitor
education, there are panels with educational text located at
various locations along the boardwalk. This provides
teachers and students a first hand opportunity to observe
and learn about the importance of wetland preservation.
It’s also a good demonstration of environmental stewardship
by a large corporation. |