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Bear
Creek Trail Permeable Asphalt |
In 2006, the City constructed a new trail along Bear Creek between
Redmond Way and Avondale Way NE, behind the Bear Creek shopping center.
The south end of this trail, adjacent to Redmond Way is made of
permeable
asphalt. The north end of the trail is made of traditional
impervious asphalt. Permeable asphalt offers a powerful tool in the toolbox for stormwater
management.
In the natural environment, rainfall sinks into soil, filters through it,
and eventually finds its way to streams, ponds, lakes, and underground
aquifers. The built environment, by way of contrast, seals the surface.
Rainwater and snowmelt become runoff which may contribute to flooding.
Contaminants are washed from surfaces directly into waterways without
undergoing the filtration that nature intended. For these reasons,
managing stormwater is a significant issue in land use planning and
development. Stormwater management tools can serve to mitigate the impact of
the built environment on natural hydrology. Unfortunately, however, they
also can lead to unsound solutions such as cutting down stands of trees in
order to build detention ponds. Permeable asphalt pavements allow for land
development plans that are more thoughtful, harmonious with natural
processes, and sustainable. They conserve water, reduce runoff, promote
infiltration which cleanses stormwater, replenish aquifers, and protect
streams. A typical permeable pavement has an open-graded surface over an
underlying stone recharge bed. The water drains through the permeable asphalt
and into the stone bed, then, slowly, infiltrates into the soil. If
contaminants were on the surface at the time of the storm, they are swept
along with the rainfall through the stone bed. From there they infiltrate
into the sub-base so that they are subjected to natural processes that
cleanse water.
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