Nov 20 2014 3:30 pm Workshop on Beach RenourishmentMiami Dade County Beaches
Beach Quality Sand
Types, Origins and Characteristics
Miami-Dade County Dept. Regulatory & Economic Resources
Division of Environmental Resources Management (DERM)
Presentation Overview
A.Benefit of Beaches
B.Miami Beach Sands.
C.Beach Quality Sand Characteristics and
Sources
D.State of Florida Sand CCCL Program and Sand
Quality Criteria
E.Chemical Quality of Sands
F.Benefits of Use of Native Sands
G.Non-Domestic Sand Source Investigations
The Benefits of our Beaches
Storm Protection and Sea Level Rise Mitigation
•
Provides protection from winter and tropical storms
–
and hurricanes
Protects over $100 billion in real estate and property
•
(http://www.insurancejournal.com/magazines/features/2013/06/17/295207.htm)
Natural system element in battle against SLR
–
Creates habitat for many species, including
•
threatened and endangered species
Sea turtles, dune plants, shore birds
–
Creates recreational and tourism opportunities.
•
Over $300 mil. spent on beaches in Miami-Dade
•
What and Where is our Beach
The “beach” (sand) extended west past Collins Ave.
and large deposits still exist under developed areas.
Miami Beach 1918LUMUS PARK 1930
Miami Beach –Pre Renourishment
(1960’s)
Native Miami Beach sand had a more golden color
Sand Characteristics
Beaches play significant physical and environmental roles,
that require the right combination of characteristics.
’:
‘Grain size
•
The larger the average (mean) grain size, the more resistant to
erosion forces. Normally sand will be in the Course-medium to Medium-fine
range.
‘Silt’ Content:
•
Silt (very fine particles) in the sand causes ‘turbidity’ in the
water that can hurt corals and marine life, dustiness on the beach. The sand
criteria requires the sands placed on the beach to have less than 5% silt;
however, the less silt, the better.
Mineral Composition
•
:
Native Miami Beach sand is ~ 40% quartz and
~60% carbonate. In general, sands should create a similar mixture of quartz
and carbonate sands
Color
•
: The color of the sand affects the temperature of the sand, which can
have esthetic and environmental consequences; not too dark, not too light
State Requirements for Beach Sand
The State requires that sand to be placed on the beach
•
meet the requirements listed in Florida Administrative
Code (F.A.C.)
(62-41.007(1)(j) F.A.C.)
Sand analysis (grain size) must be submitted and
•
approved by the State prior to being placed on the beach
State Requirements include:
•
No more than 5% ‘silts, clays & muds’ (very fine materials)
–
No more than 5% ‘fine gravel or larger’ (pebbles & rocks)
–
The color of the material comparable to ‘existing sands in the coastal system’
–
Miami-Dade and the Army Corps of Engineers have
•
additional ‘Color’ requirements, based on standard
“MunsellSoil Color” system
.
Excludes very dark and highly colored sands
–
Sand Quality
The State requires that sand to be
•
placed on the beach has minimal
silt and acceptable range of grain
‘Grain Size Curve’
indicating 95.5% of
sizes
sample was Coarse to
fine sand
‘Grain Size Analysis’ is used to
•
evaluate the suitability of the sand
Native Beach Sands have:
•
Medium to Medium fine Sand particle
–
size (Grain Size)
Normal ‘Grain Size
Distribution’ indicating
Less than 5% ‘silts’ (often less than 2%)
–
the range of grain sizes
on the beach.
Less 5% ‘fine gravel’ (often <1%)
–
The color of the material comparable to
–
existing ‘sands in the coastal system’
Summary of Grain Size Analysis
‘Grain Size Analysis’ indicates
average silt content is <2.0%
Beach Sands in Miami-Dade County
Sands considered for renourishment in Miami-Dade:
1.Native Sand
(40% quartz; 60 % CaC0); Brownish orange, small
3
deposits of this sand still remain east of Collins Ave.
2.Renourished Sand
(100% biogenic CaC0); Grayish, from
3
offshore deposits. These resources have been exhausted.
3.Mixed Sands
Renourished/aragonite sand, light gray
4.Aragonite Sand
(100%
depositional CaC0); Very light
3
color, from the Bahamas and
12
Caribbean
5.Regional Sand Source
(100%
43
carbonate, from St. Lucie and
Martin Counties
Potential Regional Sand Sources
Potential sands form St. Lucie and Martin Counties: US Army Corps of Engineer’s
‘Sediment Assessment & Needs Determination (the “SAND Study”).
For potential use in 2017 Renourishment. Final report expected: May 2015
.
SAND Study; SAND Study; SAND Study; SAND Study;
Site 14-29Site14-14Site 14-33Site 14-26
Miami-Dade Beach Sands
Offshore Miami-Bal HarborNative Sand Native Sand
Dade SandRenourished 2014‘Ocean Chateau’‘Surf Club’
Potential Regional Sand Sources
Potential sands form St. Lucie and Martin Counties: US Army Corps of Engineer’s
‘Sediment Assessment & Needs Determination (the “SAND Study”).
For potential use in 2017 Renourishment. Final report expected: May 2015
.
SAND Study; SAND Study; SAND Study; SAND Study;
Site 14-29Site14-14Site 14-33Site 14-26
Miami-Dade Beach Sands
Offshore Miami-Bal HarborNative Sand Native Sand
Dade SandRenourished 2014‘Ocean Chateau’‘Surf Club’
State of Florida “Coastal Construction
Control Line” (CCCL) Program
Beach front developers (i.e., working east of Collins or Ocean
•
Drive) must obtain a CCCL Permit (161.053 Florida Statutes)
If ‘Beach compatible sand’ is excavated during the project east
•
of the CCCL (located approximately midway between Collins
and the ocean). The sand must be placed on site and/or East of
the “Erosion Control Line” (the line that delineates public (to
the east) and private (to the west) lands)
Sands must be tested and approved prior to placement
•
Sands are placed at developer’s expense.
•
Normal quantities of beach quality sand made available range
•
between 1,000 -20,000 cy
What is in the Sand?
•The State requirements (62b-41.007 F.A.C.) that the material to be
placed on the beach shall not contain “Construction debris, toxic
material or other foreign matter”. No explicit tests or methods for
assessment are provided.
•Recent placement of sand from an excavated area with a history of
varied land use raised questions of potential contamination
•Test found no evidence of contamination, with all compounds being
either not detected, at very low or background concentrations
•Background (naturally occurring) levels for Arsenic in the coastal regions are
higher than inland regions of the State.
•Arsenic concentrations in the sand were above the State-wide ‘Soil Clean-up
Target Level’ (62-777 (F.A.C) Residential Limit.
•Independent toxicologists & FDOH stated the levels of Arsenic in
beach sand were ‘natural’ and the concentrations poses no
increased cancer risk to adults or children
Natural Variations in Arsenic Levels
•The concentrations of Arsenic (AS)
vary by region throughout the
County
•Coastal Regions have higher
concentrations than Inland areas.
•Miami-Dade Co. DERM
documented ‘background’ levels in
the coastal areas
•Concentrations ranged between 1
and 15 mg/kg, averaging 5.2 mg/kg
•The ‘Soil Clean-up Target Level’
Residential Limit of 2.1 mg/kg (62-
777 (F.A.C))
•Independent toxicologists & FDOH
stated the levels of AS in Beach
sand poses no increased cancer
risk to adults or children
Chemical Contamination Assessment
of Native Sands
Ocean Chateau stockpile (Sunny Isles) –May 19, 2014
Sand Sources for Future Renourishment
in Miami-Dade
•Miami-Dade has depleted its offshore sand
deposits that have been used for beach
renourishment
•Presently awaiting final ACOE ‘SAND’ Study to
identify sand to be used on M-D Beaches
•US ACOE estimates 23.3 million cy needed for Miami-
Dade Beaches over the next 50 years
•Sand sources far away (off Martin Co. and St. Lucie Co.)
•Quality of the majority of sand (blackish-gray) not
acceptable
•Cost of renourishment will increase 300-400%
Native Miami Beach Sand
Surfside Beach
May 9,2014
Native Miami-Dade Sand
‘Offshore’ Sand used
for renourishement
Use of Native Sand on Miami Beach
•Native sands have been placed at multiple locations in the
past, including of the Fontainebleau Resort
•Recent placement of native sand in front of the Beach Club 8
•54 th Street region has shown significant erosion.
•Large scale renourishment project is still a minimum of 2
years away, and sand source is uncertain.
•20,000 cy of native sand is presently stockpiled and ready for
placement that can be used at 54 th St. area
•Sand deposits are clean, high quality beach sand
•Use of the sand would save ~$750,000 to $1,000,000 that
would be required to purchase equivalent volume of sand to
address the erosion at 54 th St.
Use of Native Sand on Miami Beach
Source of significant quantities high quality beach
•
sand
Use of native sand deposits has proven to be a
•
means of augmenting beach renourishment and
maintaining storm protection, and maintaining the
Storm Protection and Environmental Benefits of the
Beaches
Continued utilization of sand sources made available
•
through the CCCL and similar processes can result in
savings of multiple millions of dollars, while
maintaining our defenses against storms &
enhancing our environmental, recreational and
tourism benefits.
Non-Domestic Sand Use
Investigations
•MDC is investigating potential use of non-domestic sands
for beach renourishment.
•Federal government is precluded by law to use non-
domestic sources until all domestic sources are exhausted
or excluded from consideration
•Discussion with entities in the Bahamas and other
Caribbean locations show promise
•High quality, clean sand that meets all criteria
•Initial cost estimates are comparable to present costs ($45-55 cy)
ook to seek public/private partnership for test project in
•L
Miami Beach.
Questions
?
FDOH Statement
(excerpt)
The Florida Department of Health (FDOH) has determine there is an
extremely low risk of health effects due to the arsenic found in the sand of
the Surf Club (Town of Surfside) in Miami-Dade County. The maximum
arsenic level found in the Surf Club sand (8.9 parts per million [=mg/kg])
may lead to an additional risk of developing cancer of eight in 1 million, or
eight additional cancers in a million people exposed daily to the soil over a
lifetime (70 years)*. To put this into perspective, the baseline risk for
develop any cancer in the U.S. is 0.4 or 40%. The additional risk from this
exposure could change the risk from 0.400000 to 0.400008 for a person
exposed over their lifetime to this sand. Other serious, non-cancer, health
effects are not expected* at this low level exposure to arsenic for children or
adults.
* Emphasis added