LTC 431-2019 Overview of Bioswale MethodMIAMIBEACH
OFFICE OF THE CITY MANAGER
NO. LTC# 431 -2019
LET; R TO COMMISSION
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TO: Mayor Dan Gelber and Members of e City C
FROM: Jimmy L. Morales, City Manager
DATE: August 2, 2019
SUBJECT: Overview of Bioswale Method
mission
The purpose of this Letter to Commission is to provide an overview of a bioswale design,
objectives, benefits, and limitations.
Bioswales can improve stormwater runoff quality by allowing sediments and other deposits to
settle out of the water naturally in the bioswale retention area and the engineered soils beneath
the surface of the basin. Bioswales help to reduce the velocity of water by slowing down and
retaining water, treating the stormwater before it passes into the stormwater system and
eventually the waterways and ecosystems.
In the Urban Land Institute's Technical Advisory Panel Report, it is recommended that the city
integrate flood management into the larger resilience strategy, to holistically move to a "living
with water" approach and to actively use green space to enhance permeability citywide. Jacobs
Engineering has been retained to develop an integrated water management approach. Jacobs'
first task order is to evaluate blue and green infrastructure and provide guidance on how to best
utilize these approaches. Bioswales will be a green infrastructure method evaluated by Jacobs.
This task order will be complete by October 2019.
BENEFITS
LIMITATIONS
Effective removal of suspended solids,
nutrients (nitrogen and phosphorus) and other
pollutants before it enters the bay.
Bioswales are not intended to solve water
quantity issues; thus, flooding would not be
completely addressed by a bioswale.
Allows stormwater infiltration to replenish the
fresh water lens beneath the ground
Periodic maintenance is required to preserve
vegetation, grading, and permeability.
Can capture the first flush (1.5- inches) of
runoff of rain events to remove contaminants.
Only the first 1.5 inches of large rain events
will be captured — excess water will bypass the
bioswale due to limited capacity; however, this
adequately treats contaminated runoff per
county and state regulations.
Beautifies the area with attractive landscape
and utilizes a variety of native plants to
minimize maintenance requirements.
Potential loss of parking if bioswales are
placed in right -of -way areas currently being
used by property owners for parking.
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Several examples of typical bioswale designs in public spaces:
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