Item Coversheet

Committee Assignments - C4  J




COMMISSION MEMORANDUM

TO:Honorable Mayor and Members of the City Commission 
FROM:Commissioner John Elizabeth Aleman 
DATE:June  5, 2019
 



SUBJECT:REFERRAL TO THE SUSTAINABILITY AND RESILIENCY COMMITTEE AND THE JUNE FINANCE AND CITYWIDE PROJECTS COMMITTEE TO DISCUSS A BIOSWALE PILOT PROJECT FOR 59TH STREET WEST OF ALTON ROAD.

ANALYSIS

Please place on the June 5, 2019 City Commission Agenda, a dual referral to the June Sustainability and Resiliency Committee (SRC) and the June Finance and Citywide Projects Committee (FCWPC) to discuss a potential bioswale pilot project for 59th Street west of Alton Road.

A probable component in the City’s future Design Criteria Package influenced by blue and green infrastructure, bioswales can alleviate small-scale flooding concerns. Wade Trim has provided the City with the attached rendering and a planning-level cost estimate for this pilot project of $850,000 to design and construct three different types of bioswales in immediate proximity to on another so that the administration can monitor and measure their relative efficacy and residents can observe bioswales in a neighborhood-built residential context.

 

Bioswales have the following benefits and limitations:

 

BENEFITS

  • Effective for the removal of suspended solids, nutrients (nitrogen and phosphorus), and of other pollutants from stormwater before it enters the bay.
  • Allows stormwater to infiltrate into the ground and replenishes the fresh water lens beneath Miami Beach - this supports robust green spaces.
  • Captures the first flush (1.5 inches) of runoff from every rain event to remove contaminants.
  • Beautifies the area with attractive landscape and utilizes a variety of native plants to minimize maintenance requirements.

LIMITATIONS

  • Not intended to solve flooding in problem areas.
  • Bioswales are designed to achieve pretreatment and/or water polishing. When coupled with drainage infrastructure, bioswales can be an important component of a comprehensive stormwater management strategy. 
  • Periodic maintenance is required. For example, the mulch layer will need to be replaced to maintain functionality.

It should also be kept in mind that 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.

 

For additional information, please contact my office at extension 26437.

Legislative Tracking
Commissioner John Elizabeth Aleman

ATTACHMENTS:
Description
Bioswale Rendering
Bioswale Basis of Design
Bioswale Tree Palette