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The purpose of a stormwater
retention system is to retain as
much of the rainwater in the
native soil as possible while
facilitating proper filtration of
any excess runoff during storm
events.
More about this project is in this Facebook Album:
http://bit.ly/RBCTransport
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The retention system allows
any excess runoff from the
site’s parking lots during rain
events to be filtered then
directed to the city’s storm
drain.
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At the recently completed project for
RBC Transport Dynamics, the city
storm drain empties into the Pacific
Ocean.
This project has a bio-swale and
permeable concrete. Permeable
concrete is often referred to as
“magic concrete."
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Part 1: Bio-Swale
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Step 1: Prepare Trench.
This is the first cut of the bio-swale
trench. In totality it's about 24" deep.
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Step 2: Line the Trench with Filter Fabric.
Step 3: Place and connect 20' sections of pipe,
then wrap with Filter Fabric, and place on top of
Filter Fabric at the bottom of the trench.
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Step 4: Add Aggregate
125 tons of aggregate is added to the trench and put on
top of the wrapped perforated pipe. This aggregate
filters the storm water before it is fed through the pipes
that eventually end up into the ocean.
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Step 5: Add Dirt & Form the Bio-Swale.
Dirt is gingerly placed, though with heavy equipment,
on top of the aggregate. This is a delicate process as
the filter fabric cannot be ripped or displaced during
this step.
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Step 6: Plant Vegetation
The design-build landscape architect chose plants that are
able to consume and filter much of the parking lot runoff
before it enters the storm drain system.
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Part 2: Permeable Concrete
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Step 1: Prepare Trench.
Step 2: Line Trench with Filter Fabric.
Step 3: Place and connect 20' sections of
unwrapped perforated pipe.
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Step 4: Connect small perforated pipe to the larger pipe which is
the main drain pipe.
The white perforated pipe receives water, filtered through the
layers of aggregate, underneath the permeable concrete and
feeds into the black pipe.
The black pipe directs the water away from the catch basin shown
in this photo, toward the east, connecting into a larger pipe that
runs the length of the site.
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Step 5: Place Aggregate
This is a view of the #57 aggregate over the
perforated pipe.
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Step 6: Measure Twice, Pour Once.
The worker is standing on the 18" layer of #57 aggregate and
he's showing there is 18" remaining. The next 6" layer will be
of #8 aggregate followed by 6" of permeable concrete. That
leaves 6" of concrete curb in this section of the parking lot.
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Step 7: Place 6" of #8 Aggregate.
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Step 8: Pour 6" of Permeable Concrete
In this photo, the team is pouring permeable
concrete, at a thickness of 6", over the #8
aggregate.
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Step 9: Power Screed, Add Control Joints, & Cover with Plastic
The plastic is laid out first and is placed over the screed (leveled)
concrete once the control joints have been added. The plastic
sheeting retains moisture within the permeable concrete while it
cures for seven days.
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This is what finished permeable concrete looks like.
Notice that it is porous, not troweled-tight like
conventional concrete. This concrete should NEVER
receive a slurry coating!!!
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Step 10: Stripe and Park
Once the permeable concrete has cured it is able to be
striped along with the rest of the parking lot. After the
paint dries, you're free to park your car.
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