Excerpt from: ABOVE THE FALLS --
A Master Plan for the Upper River in Minneapolis
-------------- Water
Filtration Parks: Retention and filtration of
stormwater run-off is a crucial component of an ecosystem
approach to improving the Upper River. However, sites devoted
to improving water quality should be designed and
constructed, not as simple exercises in engineering, but as
additional amenities complementing the river and adjacent
redevelopment. The concept of water filtration areas as parks
has reached an exciting level of development, with stormwater
ponds utilized as water bodies within open space settings
designed for human interest and education. The Master Plan
combines no-build zones reserved as view corridors to the
river and downtown with Water Filtration Parks. These
filtration parks are connected to the overall parks system,
and in most cases should be designed to blend t ogether
seamlessly. However, most of the land utilized for ponding
would not be owned by the Minneapolis Park and Recreation
Board, but rather should be outlots within private
development sites set aside for ponding. An option for future
consideration mig ht be the establishment of a public-private
partnership to develop ponds and allow public access.
------- Features:
Water quality ponds have such great potential as park
features precisely because they store water, which has been a
traditional part of park and pleasure garden design since
their origins. The ecological, regulatory, and aesthetic
converge, with a sharing of costs for pond construction
between what is required to meet standards and the addition
of certain public amenities to produce us eable parks. In
addition to retention ponds, other basic features should
include: -- Wetland plantings for increased ecological and
aesthetic effect, -- Observation platforms, -- Trails, --
Educational signage.
------- A Model:
As concern about water quality grows, municipalities around
the globe have recognized the opportunity to combine
stormwater ponds with parks. Many examples could be listed,
but one new park is so outstanding that it provides the best
model for a high-quality water filtration park. This park is
the "Living Water Garden" in Chengdu, China, winner
of the 1998 Top Honor Award from The Waterfront Center. The
Living Water Garden transformed a polluted riverfront site in
a highly urbanized area into an amenity that both cleans
river water and educates visitors about the processes used.
The park combines the finest in design - it is shaped to
resemble a fish - with excellent engineering, utilizing an
advanced constructed wetlands system to treat the water.
Flowing through a series of ponds, or tanks, the water is
purified by settling, anaerobic microorganisms, aeration, and
a variety of wetland plants.
------- "Living
Machine" Wetland Garden: An advanced
constructed wetlands system is applied to the River City site
in the Upper River Master Plan. Labeled the \ldblquote Living
Machine,\rdblquote after wastewater systems developed by John
and Nancy Todd, the system utilizes inert filters and
biological processes of living plants and microscopic animals
to cleanse stormwater. The urban design of the water
filtration park complements the surrounding high-intensity
uses, collecting run-off from the area\rquote s impervious
surfaces. The concept is the same as the wetlands park in
China: a system of settling tanks and filters are combined
with concrete-lined wetland "ponds." On this site,
impervious tanks or "ponds" are recommended given
the possibility of remaining soil contamination - water might
only pick up more pollutants if allowed to filter through to
the level of groundwater. The primary filters and settlement
tanks remove grit and solids in the water, while anaerobic
microorganisms in the tanks break down organic pollutants.
The water would flow from one tank over a series of cascades,
the splash and aeration increasing dissolved oxygen levels.
The secondary filtration is provided by a series of ponding
tanks with wetland species, and associated microorganisms,
taking nutrients out of the water as they grow. The China
system harvests wetland plants grown in the nutrient rich
water for use as fertilizers and feed. The "Living
Machine" would also require periodic maintenance. During
winter the flow would slow or stop, as does the flow of
surface run-off. In addition to water quality benefits, the
"Living Machine" would provide an educational
resource informing citizens about efforts and techniques
utilized to clean stormwater. Signage would describe the
various filters and plant species, and the improvements that
each stage makes to the water quality. Finally, the last
phase of treatment includes a fish pond , which could have
ornamental fish or river species, leading to a large pool and
fountain above the Skyline Amphitheater, providing a final
burst of aeration to increase oxygen content before the water
is allowed to flow to the river.
------ Other Water
Filtration Parks: Of course not every water
filtration park should be as elaborate as the proposed
"Living Machine". Most parks would consist of
simple one- or two-cell ponds, with wetland plantings, in a
naturalized setting. Some might include aeration fountains or
other devices to improve water quality. New techniques are
sure to be developed over the implementation period of the
Upper River Master Plan, yet the goals of improving water
quality, creating wetland habitat, and education will remain
constant.