| | | | | | | |  | Resolutions - C7 L
COMMISSION MEMORANDUM |
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| | | | | | | | | TO: | Honorable Mayor and Members of the City Commission | | | FROM: | Jimmy L. Morales, City Manager | | | DATE: | October 18, 2017 | | | |
| | SUBJECT: | A RESOLUTION OF THE MAYOR AND CITY COMMISSION AMENDING BOTH THE CITY’S PUBLIC WORKS MANUAL, AND THE CITY’S 2011 STORMWATER MANAGEMENT MASTER PLAN (PLAN) TO INCORPORATE MODIFICATIONS TO THE STANDARDS FOR THE CONSTRUCTION OF NEW ROADS, STORMWATER SYSTEMS, AND DEVELOPMENTS IN ORDER TO INCREASE THE LEVEL OF PROTECTION TO PROTECT FROM A 10 YEAR/24 HOUR STORM EVENT; AND WHICH MODIFICATIONS ARE ATTACHED HERETO AS COMPOSITE EXHIBIT A. |
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| | | | | | | | ANALYSIS
| Over the past several years, the City enacted several measures which created the City’s Stormwater Management Master Plan (Plan) [Resolution 2012-28068, November 14, 2012], and subsequently adopted several standards that have been incorporated into the Plan.
The Plan is intended to be a guide for improving the City's stormwater management system performance for the next 20 years, while taking into consideration potential sea level rise over the next 20 years and the impacts sea level rise would have on the City’s stormwater infrastructure.
The Plan also contemplates a 50 year planning horizon relating to seawall heights, and increasing heights of sea walls due to the sea level rise projections.
On February 12, 2014, the City adopted Resolution 2014-28499, which approved the recommendation of the Flooding Mitigation Committee to amend the Plan so as to modify the design criteria for the water level in Biscayne Bay to be increased from 0.5 Ft-NAVD to 2.7 Ft-NAVD for all tidal boundary conditions.
On June 8, 2016, the City adopted Resolution 2016-29454, which approved the recommendation of the City’s consultant, AECOM, to amend the Plan, specifically Section 2.5.3 to include future crown road elevation of 3.7 feet NAVD and a level of service such that the crown of the roadway is not overtopped during a 5 year / 24 hour design storm event with a 1.25 safety factor using the South Florida Water Management District (SFWMD) nomograph or 6 in ches times 1.25 for a total of 7.5 inches of rain.
On September 28, 2017, the Mayor’s Blue Ribbon Panel on Flooding and Sea Level Rise voted to make a recommendation to the City Commission to amend the Plan, and the City’s Public Works Manual, so as to further increase the City’s stormwater level of service for roadways, such that the future crown of road is not overtopped (flooded) during a 10 year/24 hour design storm event using the SFWMD nomograph or 7 inches times 1.25, which equates to 8.75 inches of rainfall as opposed to 7.5 inches of rain previously adopted.
The Mayor’s Blue Ribbon Plan on Flooding and Sea Level Rise, and the City Administration support the modification to the Plan.
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| | | | | | | | CONCLUSION
| The Administration recommends that the Mayor and City Commission of the City of Miami Beach, Florida accept the recommendation of the City Manager to amend the 2011 Stormwater Management Master Plan.
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| | | | | | | | Legislative Tracking
Public Works |
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| | | | | | | | Sponsor
Commissioner Joy Malakoff & Co-sponsored by Commissioner John Elizabeth Aleman |
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