LTC 236-2007 Beach Renourishment: Sand Back-passing ProjectI~~C'I~ I~.lF~~
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m I~11 AN11 BEACH CITY CL~~,~~s cF ~ Ic,
OFFICE OF THE CITY MANAGER
NO. LTC # 236-2007 LETTER TO COMMISSION
TO: Mayor David Dermer and Members of the City Commission
FROM: Jorge M. Gonzalez, City Manager
DATE: October 29, 2007
SUBJECT: Beach Renourishment: Sand Back-passing Project
The purpose of this LTC is to provide an update to the Mayor and City Commission on the
beach renourishment activities undertaken on our beaches until the end of the year.
Previous Sand Relocation Projects:
In 2002, the 32nd Street breakwater structures were constructed in order to decrease the
rate of erosion at this hotspot location. Approximately 125,000 cubic yards of sand were
excavated from the Lummus Park shoreline and used to backfill behind the breakwater
structures to create a stable and wide beach area in the hotspot, which had experienced
severe constant erosion previous to the construction of the breakwater. For that project,
material was loaded into all-terrain dump trucks and transported north to the breakwater site.
While this method was very cost effective, it was operationally disruptive to our beachgoers
and created safety and environmental concerns.
Sand Back-passing from Accretiona/ to Erosional Areas:
The southern portion of Miami Beach, from approximately 22~d to 5th Streets, have been
accretional (accumulating sand) since the initial major sand renourishment project was
completed in the 1980's. The County commissioned a study to determine the feasibility of
sand back-passing, or passing sand from southern accretional areas to erosional areas in
the north, in order to further investigate the concept of relocating excess sand given the
scarcity of off-shore sources. The Miami-Dade County Morphological Change Study (Coastal
Systems International, Inc. study of the coastline completed in 2006) stated that
approximately 60,000 cubic yards per year could be back-passed (pumped from south to
north) from the Lummus Park shoreline north to erosional areas without impacting the
existing shoreline and provide a very cost effective source of sand for relatively small
nourishment projects.
In order to evaluate alternative methodologies for back-passing sand, Miami-Dade County
contracted with a consulting firm to provide an analysis of methodologies and their
associated cost. The analysis evaluated the feasibility, cost-effectiveness, and level of safety
and disruption associated with moving the sand hydraulically (by pumping) to areas in need
via water- orshore-based dredging, trucking, and other methods. This report was completed
in November 2006. In anticipation of this report, Miami-Dade County included a funding
request in its FY 2007-08 State Beach Erosion Capital Plan to provide for the
implementation of sand back-passing projects from accretional areas in the south to
erosional areas to the north.
In December 2006, the County awarded the contract to SubAqueous Inc. to provide earth
moving services, including the excavation and transport of sand as needed for the Sand
Back-passing Project. The project has obtained all necessary permits from the Army Corps
of Engineers (ACE), Florida Department of Environmental Protection (FDEP), and Miami-
Dade County Department of Environmental Resources Management (DERM). The County
expects to begin work after October 31st, 2007, observing the end of Turtle Nesting Season
on Miami Beach, as the FDEP permit stipulates. The City will issue a ROW permit for the
project this week and mobilization by the Contractor west of the dune will be permitted at
such time. However, work east of the dune will not be permitted until after acity-sponsored
community meeting is held on Friday November 2"d, which DERM will attend. The project is
estimated by the County to last approximately 30-45 days, concluding inmid-December. The
Sand Back-passing Project will replace the truck hauling project currently on-going at 29tH
Street.
The pro~ect scope includes the dredging of sand material from the beach area between Stn
and 15t Street, the transport of this sand via truck along the hard-pack to a dredge pit
located at 13th Street, the entrenchment of a pipe adjacent to oceanfront side of the dune,
and the pumping of dredged sand through the pipe north to the area between 22~d-29tH
Street. Please see attached site plan for details. The contractor will remove accreted sand
as per the cross-section detail attached. Each excavation area relates to a grid cell on the
site plan and will measure 150 feet in length by 150 feet in width. Each grid cell should take
approximately 1-2 days to completely excavate and re-grade to specified slope and surface
conditions. The contractor will use pay loaders and all terrain vehicles to transport the sand
to the pit area from the excavation area. The sand will then be pumped through an
underground pipeline that will empty onto the 22"d-29tH Street beach area. Bulldozers will
then grade the sand to the approved slopes in the area between 22~d and 29tH Streets, or the
area just south of the southernmost breakwater installation. The contractorwill use hospital-
grade mufflers on the dredge and booster pump equipment in order to minimize noise levels.
The County will have afull-time construction inspector for the duration of this project.
The contractor has submitted a Maintenance of Traffic (MOT) plan and a Work Plan, on
which Staff has provided comment to DERM relative to public safety and minimization of
impact to residents and tourists using the beach during construction. Staff has coordinated
and participated in several meetings with the leadership of the Ocean Drive Association, the
Boucher Brothers, and DERM officials regarding this project. A public pre-construction
informational meeting is scheduled for Friday November 2, at 1:00 PM at the Miami Beach
Police Department Community Room.
Miami Beach Truck Haul Nourishment Project: This project was developed as a relatively
small nourishment of three localized erosional hotspots located at approximately 29th and
44th Streets in Miami Beach. The Project started in April of 2006. The projectwas conducted
using sand trucked in from inland quarries in Central Florida. Due to limited truck access
points onto the beach, and the need to handle the sand several times, the rate of sand
placement on the beach was relatively low and somewhat inefficient. As a result of this, and
the beginning of the seasonal increase in beach tourism, construction was discontinued on
December 1st, 2006. The project was restarted in July 2007 and will continue on through the
end of Dece ber at a 44tH-46tH Street location.
JMG/ F V/leb
F:\work\$ALL\(1) EMPLOYEE FOLDERS\LISA BOTERO\BEACH RENOURISHMENT\LTC Sandbackpassing 10.24.07.doc
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