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Since its inception more than
50 years ago,
The Wissahickon Valley Watershed Association (WVWA) has promoted
intelligent land use practices, preservation of environmentally
sensitive and historic sites, and has worked on public education
initiatives. The WVWA now maintains more than a thousand acres of
preserved land in the Wissahickon
watershed.
To provide enhanced stormwater
management on its properties, WVWA implemented the following BMPs: 1)
Porous paving; 2) Dry well;
3) Rain barrels; 4) Constructed wetland.
Photos of the BMPs taken by Bob Adams follow.
1) Porous Paving
Plastic pervious paving grids were installed on the grounds of WVWA’s
headquarters in 2002 and concrete paving grids were installed in 1991.
The earth was leveled at approximately one foot below existing grade and
filled with fist-sized stone to create stormwater storage capacity.
These grids allow for water and pollutants to penetrate the soil
underneath the grid, while still providing structural support for
vehicles. Because grass grows within the grid squares, the area is
natural looking, retains much less heat than traditional asphalt and
reduces the velocity with which stormwater flows off the surface of the
ground. Since stormwater has time to percolate into the ground and
filter, pollutants associated with parking lots are not washed right off
of pavement into waterways. Mowing is the only maintenance work
required. Click
here
for a picture of WVWA's concrete pervious pavement. Click
here
for a picture of on site plastic pervious pavement.
2) Dry Well
A dry well was built to effectively retain excess drainpipe water during
periods of excessive rainfall. To build a dry well the WVWA dug a hole,
used grid left over from the pervious parking grid to create a frame,
filled the hole with riverstone and placed a 4” PVC pipe on end.
Click
here for
a photo of WVWA's dry well.
3)
Downspout disconnect and Rain Barrels
Rainwater falling on Four Mills Barn is collected from drain pipes and
is stored in twin rain barrels. This water is recycled by serving as a
reserve for watering plants on site. WVWA disconnects the drain pipes,
drains, and seals the rain barrels during the winter to prevent damage
from freezing. Click
here for a
photo of one of WVWA's rainbarrels.
4) Constructed Wetland
The wetland area along Sandy Run was a strategic area to retrofit
because of its high visibility to the public, the high magnitude of stormwater runoff in its vicinity, and the tributary is a
contribution of non-point pollution flowing into the Wissahickon Creek. The wetland’s first phase was started in Spring
2006. Trees were planted upstream from the wetland in order to cool the
water temperatures in the creek, increasing oxygenation. Within the
wetland itself, clay silt, which had been deposited over the years, was
removed with the help of heavy machinery. The wetland’s bottom was
somewhat staggered in height to create different zones for various
aquatic plants. Native wetland vegetation was restored within the basin
and a vegetative riparian buffer was created. Since geese are often
intrusive and destructive to wetland projects, design strategies to keep
them away included tall wetland plants, a vegetative buffer, and geese
barriers. Geese barriers, made of stakes and string forming a grid
system, also were installed to prevent both geese and deer from
consuming juvenile plants.
Interpretive signs are planned to be placed on site
in the near future. Other plans for the site include an extension of the
Montgomery County Cross Country Trail alongside the wetland. The
wetland’s total area doubled in 2008 with a large-scale expansion
project. For a plant list for the constructed wetland, click
here. The newly
planted herbaceous plants are thriving and the newly planted trees and
shrubs require watering during their first year before they are
established. The wetland’s maintenance
plans over the first five years otherwise include the inspection for and removal
of invasive species. In 2009 Galerucella beetles will be released
to take care of the purple loosestrife invasion.
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