2017-30039 Resolution RESOLUTION NO. 2017-30039
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.
WHEREAS, 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; and
WHEREAS, 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; and
WHEREAS, 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; and
WHEREAS, 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; and
WHEREAS, 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 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, which modification, if adopted by
the Mayor and City Commission, would modify the existing standard in the Plan from
having the roadway service level support for solely a 5 year/24 hour design storm
event.; and
WHEREAS, the Mayor's Blue Ribbon Plan on Flooding and Sea Level Rise, and
the City Administration support the modification to the City's Plan.
NOW, THEREFORE, BE IT RESOLVED BY THE MAYOR AND CITY
COMMISSION OF THE CITY OF MIAMI BEACH, FLORIDA, that the Mayor and City
Commission amend both the Public Works Manual, and the City's 2011 Stormwater
Management Master Plan to incorporate modifications to the standards for the
construction of new roads, stormwater systems, and developments; which standards
would incorporate higher elevations in order to reduce the risk of flooding; and which
documents are attached hereto as Composite Exhibit A.
PASSED and ADOPTED this a8 day of October, 2017.
ATTEST:
P ilip a e;'Mayor
to, c '�y '
Raf.el E. Granado, City'C
, x •`>' ^;� APPROVED AS TO
FORM & LANGUAGE
8c FOR EXECUTION
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Resolutions - C7 L
MAM BEACH
COMMISSION MEMORANDUM
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.
RECOMMENDATION
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
Page 329 of 1633
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.
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.
Legislative Tracking
Public Works
Sponsor
Commissioner Joy Malakoff& Co-sponsored by Commissioner John Elizabeth Aleman
ATTACHMENTS:
Description
o FA Reso- Stormwater Master Pan
❑ Exhibit A
Page 330 of 1633
EXHIBIT A
ADDENDUM 2 TO THE CITY OF MIAMI BEACH
STORMWATER (MANAGEMENT) MASTER PLAN FINAL REPORT
The following amendments to the following sections of the 2011 SWMP are hereby
amended and incorporated by reference into the 2011 SWMP, as follows:
2.5.3 Proposed Level of Service (LOS)
As shown, CDM evaluated design storm events and joint tidal event
periods to evaluate stormwater system performance and the project
needs and costs to achieve various levels of service. The various
evaluations for LOS indicated a point of diminishing returns at the 2
to 3 year storm event level.
Therefore, the City and CDM formulated options to best protect public
safety and property with available funding. The 5-year, 24-hour design
storm of 7.5 inches of rainfall was also investigated due to current
LOS standards. As an example, a 5 year LOS in the Flamingo •Park
Lummus Avenue project area would cost approximately $80 million,
and the City available budget for this project area is approximately
$35 million.
Based on the supplied information herein, the City should determine
whether an adjustment in the design storm is prudent as it relates to
the future evaluation of LOS.
"Future crown of road"and "future back of sidewalk elevations"shall
be 3.7 feet, NAVD, unless exempt due to hardship as determined by
the Director of Public Works.
For land development purposes. "future grade"shall be a minimum of
3.7 feet NAVD.
The stormwater level of service for roadways such that the "future crown
of road'is not overtopped(flooded)during the-5-10 year 124 hour design
storm event shall be constructed utilizing the following parameters:
o South Florida Water Management District nomograph with 1.25
safety factor.
o The rainfall distribution shall be the SCS Type Ill.
o The Unit Hydrograph peaking factor shall be 150.
Page 333 of 1633