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During a recent expansion of
Perkiomen Valley High School, stormwater Best Management Practices (BMPs) were incorporated
into plans in order to manage the runoff from 28 acres
of athletic fields and impervious surfaces. Components of the plan
included: 1)
Vegetative swales; 2) Wet pond, aerator, and aquatic bench;
and 3) Maintenance plan. The full list of plantings, including
seed mixes, plugs, shrubs, and trees is available
by clicking
here.
1) Vegetated Swales
The vegetated swales are composed of a mix of meadow grasses that
accommodate runoff from the school’s 28 acres of athletic fields and
impervious surfaces. Because stormwater naturally flows to this recessed
and sloped area, the swales funnel the water down to the wet pond,
making for cleaner and calmer runoff.
2) Wet Pond, Aerator,
and Aquatic Bench
The wet pond collects water from the vegetated swales which carry
runoff from athletic fields and parking areas. The property’s soils
were not very penetrable to percolation and thus the decision was made
to allow for a pond instead of a naturalized basin. The pollutants and
sediment from the surrounding area gravitate towards the bottom of the
deep wet pond and can be removed as needed. An aerator is used to
oxygenate the pond’s water enough to sustain organisms like plants and
aquatic life.
The aquatic bench was
formed by removing the 12’ portion of top soil was removed and keeping
it safely aside. The depth of the bed needed to be dug a foot deeper
than anticipated to re-deposit the topsoil. This was done in order to
maintain the ecological integrity of the site. Straw mulch was used to
immediately stabilize disrupted areas. Warning flags were posted along
the aquatic bench and a goose fence was mounted along the shoreline. The
goose fence needed to circle the pond with stakes installed at 10-foot
intervals, and the circumference was staggered with another subsequent
row to effectively keep out the birds. Click
here
for a detail drawing of an aquatic bench by Cahill Associates.
3) Maintenance Plan
A maintenance plan was implemented to include habitual mulching, pest
control, weeding, pruning, etc. Even though a natural spring area on the
wet-pond’s steep slope was carefully planted to avoid the invasion of
cattails, by winter 2007-2008 they had grown in. The cattails are pulled
out by hand to keep them from taking over. The District saves about $100
per month by not mowing their basins.
The BMPs are used as living
laboratories, frequented by science classes learning about environmental
issues. This project is not only indicative of Perkiomen Valley School
District’s dedication to sustainable land-use, but it also stresses the District’s
commitment to hands-on education: the students play an active role in
the monitoring of the site. The naturalized sites are tested for
chemicals, pH, temperature, dissolved oxygen and species diversity.
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