051-2009 18th Street / Purdy Avenue Floodingm !U~IAMIBEACH
Office of the City Manager
TO: Commissioner Ed Tobin
FROM: Jorge M. Gonzalez, City Manager
DATE: September 25, 2009
SUBJECT: 18th Street / Purdy Avenue Flooding
MEMORANDUM
051-2009
Per your request, please find attached the stormwater outfall maps and maintenance cleaning
records of the entire Sunset Harbour neighborhood bounded by Purdy Avenue, Alton Road, Dade
Boulevard, and 20th Street.
In June and July of 2004, the Public Works -stormwater Utility Division performed the last
scheduled maintenance cleaning of the municipal separate storm sewer system (MS4) of this
neighborhood. Maintenance cleaning includes cleaning the catch basins, manholes, outfalls, and
associated small and large drainage pipe systems. Citywide the MS4 maintenance cleaning
frequency ranges from eighteen (18) months to five (5) years. The Cites MS4 maintenance program
aims to clean the small pipe systems (pipes less than 18 inches) every eighteen (18) months to
three (3) years, depending on land use of the area and the amount of debris and sediment that
enters the system from the public streets. For example, heavily used commercial districts and
residential areas that are highly landscaped require greaterfrequency of cleaning and maintenance.
The larger pipe systems (greater than 18 inches) are currently cleaned by outside contractors on a
five (5) year cycle.
The City's National Pollution Discharge Elimination System (NPDES) Permit sets forth the
stipulations that allow the City to discharge stormwater from the MS4 into waters of the state. While
the NPDES program does not stipulate the frequency of maintenance cleaning activities, it does
require the City to implement a comprehensive stormwater Management Program (SWMP) that
includes maintenance of catch basins, grates, outfalls, pipes and other stormwater structures and
roadside swales and proper disposal of accumulated sediments. In addition, the City is required to
maintain an internal record keeping system of all maintenance and cleaning activities performed
during each permit year. Each year City staff collects documentation of the Cites MS4 maintenance
activities that include a map of the drainage pipes and structures maintained during the reporting
year, field staff cleaning logs, and a record of the contractor's maintenance activities. The City's
records indicate that the cleaning maintenance cycle of the entire drainage system is approximately
3 to 5 years. The Florida Department of Environmental Protection (FDEP) is responsible for
reviewing the NPDES Annual Report for each reporting year. For reporting Year 6 (FY07-08), the
FDEP determined that the City's Annual Report was administratively complete and had no additional
comments.
The City has a Pilot Program for the installation of check valves (Tideflex) to prevent the backflow of
Biscayne Bay water into the stormwater system. In response to this recent coastal flooding event,
the City has ordered two (2) Tideflex valves for installation at the outfall pipes at 18th Street and Bay
Road, and 18th Street and West Avenue, with an estimated installation in mid-November 2009.
FHB/MA
We are cammitted to providing excellent publ+c service and safely to all who live, work, and play in our vibrant, tropical, historic community.
Attachments:
A. Stormwater Outfall Map for Sunset Harbour
B. Stormwater System Sunset Harbour ~~, ~ ~-, ~-- ~ ~~~ ~ ~°~
C. Stormwater Maintenance Cleaning Records
Cc: Mayor Matti Herrera Bower and Members of the City Commis~l~61~ SEA ~$ f ~ ~2~ ~+4
Tim Hemstreet, Assistant City Manager _
Fred H. Beckmann, P.E., Director of Public Works C11 `` Ci~i_~~~ ~f~1 s~•t-
F:\work\$ALL\(1) EMPLOYEE FOLDERSWIDA ORTIZ\Memos\18thPurdyflood.doc
We are cammi»ed to providing excellent public service and safety to all who live, work, and play in cur vibrant, tropical; historic community.