Project Rain Garden

I mentioned last week I was elected to a supervisor position with the
Pennington SWCD. I decided I would use my column to occasionally
explain SWCD projects from time to time. The agency name and its
mission are closely related; it is the Soil and Water Conservation
District. We are not saving water in large tanks for a later date,
those tanks of water exist naturally underground; rather we seek to preserve the quality
of that same water. When it rains and water flows to where it wants,
the water may pick up bits of soil or fertilizer and deposit them
into a stream or river. This is no favor to soil or water as the
soil is useless in a stream bed and water that carries soil or
fertilizer doesn’t taste right. The SWCD conserves soil by preventing
erosion and conserves water quality in the same action. Now let’s talk
about a very visible project that will attempt to accomplish these
tasks plus a bit more.

The Ralph Engelstad Arena occupies a large amount of real estate and
therefore is subject to an equally large amount of rain. When rain
falls on soil it is absorbed into the ground then is either used by
vegetation, evaporates or drains to lower elevation. When rain
falls on a building it needs to be managed or it will overwhelm the
abilities of nature to absorb, flow or evaporate which often means
erosion. We manage rain as it falls onto buildings with rain gutters and then either pump it
away our use gravity in its course to lower elevation. It is better
to use gravity as gravity doesn’t need maintenance.

The Pennington SWCD and the City of Thief River Falls, Minnesota are now in
planning stages to create a Rain Garden at the Ralph Engelstad Arena.
The project will seek to control runoff in a simple, pleasing way
that requires the least amount of continued maintenance as possible.
The current problem is that water comes off the roof, overwhelms the
current drainage and flows along the front entrance sidewalk as it
descends to the street. The excess water flow removes landscaped soil
and fertilizer which costs money to replace and it increases the
turbidity of the same water we all eventually use. The excess water
from the parking lot on the south side of the Ralph runs north to the
storm sewer in front of the building and causes flooding of the
street, so much sometimes that the water reaches the first step of
the entrance!

This picture shows a rain garden in the background complete with a curb cut in the foreground to allow excess rain into the rain garden.

The rain garden will consist of a two pits (or depressions) that are
created by removing a fair amount of clay then replacing the clay
with an absorbent sand and peat mixture. Beneath the sand and peat is
a slotted tile which will remove the filtered water and into a storm
sewer. There is no standing water in a rain garden so it does
not contribute to the mosquito population. The rain gardens will be
capable of absorbing a typical one-inch rain event. The gardens will
be covered with plants and some type of mulch. The run-off from the
roof of the Ralph will travel through a down spout, enter a drainage
structure then pass underground through an eighteen-inch pipe into
each rain garden to be filtered. Meanwhile, the water from
the parking lot will flow through a cut in the existing curb, past a
drainage structure to strain out garbage, and into a rain garden.

Both rain gardens, one on the north side of the entrance sidewalk and
one on the south, are the most visible portion of the project. The
drainage structures, tile and pipe are either underground or mostly
underground and are interconnected. There will be existing concrete
removed to bury the underground pipe. Plans exist now to add a subtle shade of blue to
the replacement concrete in an effort to remind people of the water
moving underneath their feet and the fact they no longer have to walk
through the water. I think this is a nice, inexpensive touch.
Another inexpensive touch is that much of the construction cost is
paid for by grant money.

This is a project that explains the work of the Soil and
Water Conservation District. It prevents uncontrolled water flow
which removes valuable soil and fertilizer and deposits them into the
water. It also benefits the many people who use the Ralph Engelstad
Arena as they will no longer have to walk through or around pooled
water when it rains. The rain garden will also decrease the cost of
its maintenance to the taxpayer. This is an important point as I know
people may put up with wet feet but they will not willingly weather
higher taxes.

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