1. RADICAL DAMAGE CALLS FOR RADICAL REMEDIATION: THE
SNOOK ISLANDS ENVIRONMENTAL ENHANCEMENT
PROJECT, PALM BEACH COUNTY, FLORIDA
David C. Carson
Palm Beach County Department of Environmental Resources Management
2300 N. Jog Road, 4th Floor
West Palm Beach, Florida 33411-2743
Abstract
The Lake Worth Lagoon in Palm Beach County, FL was previously a freshwater lake fed
by water from the north and west. In the 1870’s, a permanent oceanic inlet was
established near Palm Beach converting the freshwater system to an estuarine system.
Mangroves and other estuarine flora and fauna colonized the lagoon. Over the next 100
years, however, dredging, filling and bulkhead construction eliminated roughly 80% of
the mangrove fringe and much of the lagoon’s shallow water resources. In 1998, Palm
Beach County ERM began planning a habitat enhancement project at the Lake Worth
Municipal Golf Course. Dredging and bulkheading of the shoreline to create the golf
course virtually eliminated areas suitable for re-establishment of inter- and shallow sub-
tidal biotic communities. The only viable option to remediate the loss of habitat was to
place fill in the water to reconstruct inter- and shallow sub-tidal wetland grades. Peanut
Island was a ready source of dredge spoil, and an island makeover was in the final
planning stages. The Peanut Island makeover project included offloading 1.2 million
cubic yards of spoil. Over 1,560 barge loads of spoil were transported 10 miles to
construct the Snook Islands environmental enhancement project, resulting in creation of
10 acres of red mangroves, 2.8 acres of Spartina marsh, 2.3 acres of oyster reef, and ~50
acres of seagrass recruitment area. Radical environmental damage can only be remedied
through radical remediation projects. However, regulatory agencies are typically
uncomfortable with the impacts associated with projects of this type and magnitude. A
goal of this project, now that it has been successfully completed, is to encourage the
agencies to appreciate the environmental benefits of such projects.
Introduction
Over the past century, the Lake Worth Lagoon has experienced a significant assault on its
natural resources. Dredging and filling of inter- and sub-tidal resources and associated
seawall construction virtually eliminated fish and wildlife habitat in the lagoon. In an
effort to address this loss of biotic resources, Palm Beach County Department of
Environmental Resources Management (ERM) produced the Lake Worth Lagoon Natural
Resources Inventory and Resource Enhancement Study (Dames and Moore, 1990). This
study inventoried existing natural resources within the lagoon and evaluated potential
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2. future habitat enhancement projects. One site identified in the plan was at the Lake Worth
Municipal Golf Course (LWGC) in the City of Lake Worth.
Project planning for the LWGC site began in 1998. Typical past wetland enhancement
work involved excavation of upland spoil sites to wetland elevations. However, this
technique for wetland enhancement would not work at the LWGC because the uplands
were reserved for golf play. It was then that the focus of the project moved offshore. It
became clear that the only way to produce a meaningful project was to re-fill the lagoon
bottom next to the LWGC where it had been previously dredged in order to re-establish
wetland depths and grades that would support productive biotic communities.
At the same time, a project was being developed for Peanut Island, a dredge spoil storage
island located at the Lake Worth Inlet. Both recreational and environmental features were
to be constructed on the island. The island’s spoil storage was at capacity, and plans were
being developed to offload spoil from the island. It was decided to combine the two
projects, and use the offloaded spoil to re-create inter-tidal and shallow submerged
wetland grades that had been eliminated during construction of the LWGC. The project
site was ultimately named the Snook Islands enhancement site. A location and vicinity
map is shown in Figure 1.
Figure 1. Snook Islands location map.
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3. Study Site
Lake Worth Lagoon
The Snook Islands project site is located adjacent to the LWGC in the Lake Worth
Lagoon (LWL) in central Palm Beach County, Florida (Figure 1). The LWL is a 22 mile
(35.5 km) long coastal lagoon with two oceanic inlets. The Lake Worth Inlet is located
near the north end of the lagoon, and the South Lake Worth Inlet is located at the
southern end. A distance of approximately 15.5 miles (25 km) separates the two inlets.
The LWL was originally formed after the Great Ice Age. As sea levels dropped, the
offshore bars were sufficiently exposed to create a permanent barrier, completely cutting
off the inshore lagoon from the sea. Its waters became entirely fresh and stood somewhat
above sea level, with its precise elevation depending on the wetness or dryness of the
season. (Vines, 1970). Several early attempts were made to create navigable inlets to the
ocean, and in 1877 a stable inlet was excavated. Immediately the lake and its biota began
to change to an estuarine lagoon system with a mangrove dominated shoreline. Also
during this decade developers began dredging and filling the wetland edges of LWL, an
activity that would continue into the 1970s. Inter- and shallow sub-tidal resources were
decimated. Presently, 47 marinas and hundreds of private docks are scattered along the
shoreline. Approximately 65% of the lagoon shoreline is bulkheaded, while only about
19% of the shoreline remains fringed by mangroves. (Palm Beach County ERM and
FDEP, 1998).
Peanut Island
Peanut Island was originally created in 1918 using the material excavated when the Lake
Worth Inlet was created. First called Inlet Island, Peanut Island encompassed only ten
acres (4.0 hectares). By 1923 the Port was using the island as a spoil storage site for the
maintenance of the inlet and the Port shipping channel. The Port sold the northern half of
the island in 1991 to the Florida Inland Navigation District (FIND) as a spoil storage site
for Intracoastal Waterway maintenance dredging. (Palm Beach County ERM and FDEP,
1998).
Today, as a result of continued spoil deposition from maintenance dredging of the inlet
and the Intracoastal Waterway, Peanut Island comprises approximately 86 acres (34.8
hectares). The primary use of the island will continue as a spoil storage site, but the Port
Authority and FIND have made the perimeter of the island available to the public as a
park through a long-term arrangement with Palm Beach County. (Palm Beach County
ERM and FDEP, 1998).
Lake Worth Golf Course
The LWGC has approximately 1.2 linear miles (1.9 km) of shoreline along the western
shore of central LWL. The existing upland portions of the LWGC were created through
the dredging and filling of inter- and sub-tidal wetland resources and associated bulkhead
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4. construction. These dredge and fill activities along the shoreline resulted in a steep
littoral profile, with elevations dropping quickly from +4.0 feet referenced to the National
Geodetic Vertical Datum of 1929 (NGVD) at the shoreline to -7.0 feet NGVD just
offshore. This steep grade minimized the area suitable for development of inter- and
shallow sub-tidal resources such as mangroves, seagrasses, and oyster reefs. Mean High
Water at the site is +1.79 NGVD. Mean Low Water is -0.8 NGVD. Open water dredge
holes as deep as -23.0 NGVD existed prior to construction, and depths below -10.0
NGVD were common. Just over one-half of the existing shoreline is fringed with three
species of mangroves (red: Rhizophora mangle, black: Avicennia germinans, and white:
Laguncularia racemosa), inter-mixed with exotic Australian pine (Casuarina sp.) and
Brazilian pepper (Schinus terebinthifolius). The bulkhead has failed over time, leading to
erosion of the shoreline from wind and wake-generated wave energy.
Methods and Materials
Peanut Island
Construction of the project began in the summer of 2003. All vegetation (primarily exotic
species) was removed from the spoil storage area on Peanut Island. Removal included
clearing, grubbing, and chipping over 40 acres (16.2 hectares) of densely forested land.
More than 80% of the vegetation removed was recycled as mulch and spread throughout
the Maritime Hammock portion of the Peanut Island project or used for slope
stabilization in areas cleared of vegetation. The remaining vegetation was burned in an air
curtain incinerator.
Excavation of the island began immediately upon completion of clearing. Hydraulic
excavators, trucks and scrapers were used to excavate the material and transport it to the
staging area on the southwest side of the island. Trucks placed the excavated material in a
hopper which fed a conveyor system set-up for loading barges. The hopper mouth was
fitted with a grid screen on top to strain out large rocks and vegetation. From the hopper,
the material was fed onto a stacking conveyor creating a 10,000+ cubic yard surge pile.
This surge pile was placed on a surge tunnel conveyor, which fed a telescopic conveyor
system used to load the material on hopper barges for transport to the Snook Islands
project site. Once loaded, the barges were transported 10 miles south to the project site
for offloading. A photo of the barge loading operation on Peanut Island is included in
Figure 2.
While the excavation and transport of material was taking place, other crews began
construction of the island’s public use facilities. This included construction of a new
levee containment system capable of holding 300,000 cu. yds. (229,366 cu. meters) of
spoil, a weir structure, boat docks, swim platform, shallow water artificial reefs,
breakwaters, jetties, roadways, pathways, bridges, drainage systems, irrigation systems,
electrical systems, security fencing, and environmental features.
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5. Snook Islands (LWGC)
The first task was to remove exotic vegetation from approximately 5 acres (2 hectares) of
the LWGC shoreline. Once cleared, all shoreline armor (rip rap, concrete rubble, and
collapsed seawall) was removed, except in areas where the seawall was still intact. The
Figure 2. Peanut Island barge loading operation.
demolished shoreline armor was loaded on a barge, transported just offshore and
deposited in a deeper area of the dredged hole prior to filling. Approximately 1,800 ft
(549 m) of seawall was buried in-situ.
A total of 1.2 million cubic yards of fill (917,466 cu. meters) were used for project
construction. Figure 3 shows the construction plan. Over 1,560 barge loads of material
passed under three drawbridges during construction. Once the barges reached the project
site, the material barge tied up to two barges arranged in an L-shape. On one barge was a
Komatsu PC 1800 specially outfitted with an 18 yard clamshell bucket, and on the other a
hopper and conveyor system. The fill was offloaded by the clamshell bucket into the
hopper/conveyor system, and was discharged over a radial telestacker, which was
remotely controlled from the conveyor barge.
The project site was divided into 50X50 foot grid sections with predetermined fill
quantities scheduled for each grid. Material quantities and placement were monitored
using belt scales and GPS positioning software, and were continuously updated as filling
progressed. As each fill section was completed, the barges were moved to the next
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6. section with a winch along a four-point anchoring system, working from the shoreline
out. The barge set up could fill approximately 250 linear feet of shoreline before the
anchors needed to be pulled and reset for the next section. The radial and telescopic
movements of the conveyor system allowed precise placement of fill into the 50X50 foot
grid sections. A photo of the offloading system is shown on Figure 4.
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7. Figure 3. Snook Islands construction plan.
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8. Figure 4. Fill offloading and grading operation.
As each section was completed, smaller barges with long reach excavators followed
behind to ensure finish grades were within tolerances. All of the excavators used for
finish work were equipped with Trimble Site Vision ® GPS systems capable of attaining
finish grades to within +/- 2.0 cm.
As filling progressed into deeper water, the fill load became too great to be supported by
the existing mud substrate. Fine sediments had accumulated in the dredge hole over the
years, becoming as deep as 20 feet (6.1 m) in some places. As the fill load increased,
approximately 25% to 30% of the fine sediments were displaced waterward of the
operation. The contractor compensated by overfilling the template and pushing the fill
out over the slope face to cover the exposed mud.
Approximately 28,000 tons (25, 401 metric tons) of 1-3 ft (0.3-0.9 m) diameter limestone
boulder riprap was used to create the oyster reefs and mangrove planting breakwaters.
Oysters were already colonizing suitable substrate in the project vicinity at depths
between -1.5 to +1.5 feet referenced to the National Geodetic Vertical Datum of 1929
(NGVD). Oyster reefs were constructed between -2.0 NGVD and +2.0 NGVD in an
effort to encourage additional oyster recruitment. The mangrove planting breakwaters
were constructed between -1.0 NGVD and +4.0 NGVD.
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9. Approximately 12,000 smooth cordgrass (Spartina alterniflora) and 9,000 seashore
paspalum (Paspalum vaginatum) were planted 2 feet on center. The Spartina was planted
between 0.0 and +2.0 NGVD, and the Paspalum between +2.0 and +4.0 NGVD. Roughly
50,000 red mangroves (Rhizophora mangle) were planted 3 feet on center on the 4
offshore islands and on the three mangrove planters along the shoreline. The mangrove
planting shelf was constructed between +0.8 and +1.0 NGVD.
Results and Discussion
The project was completed in June 2005, and resulted in creation of 10 acres of red
mangroves, 2.8 acres of Spartina marsh, 2.3 acres of oyster reef, and approximately 50
acres of seagrass recruitment area. Project construction eliminated the original shoreline
armor along the golf course, and replaced it with a soft, vegetated shoreline. The offshore
islands and oyster reefs provided protection from wind and wave energy, stabilizing the
formerly eroding shoreline. In 2004, Hurricanes Frances and Jeanne made landfall near
the project site. Because the project was well underway, no damage was sustained to the
project or to the LWGC shoreline. Figure 5 shows an aerial view of the completed
project.
Red mangroves
The planted red mangroves achieved a survival rate of approximately 80% after two
years. The mangroves were collected as propagules by volunteers and raised in a nursery
to the 6 to 8 leaf stage. They were then planted on 10 different occasions by volunteers as
construction of the islands and shoreline planters was completed. Figure 6 shows typical
before and after photos of the planted mangroves.
Spartina
The Spartina was planted by the contractor as each section of shoreline was completed.
The plantings coalesced in approximately two years. Figure 7 shows typical before and
after photos of planted Spartina.
Oysters
Oysters (Crossastrea virginica) have colonized the oyster reefs and base of the mangrove
planting wave breaks. The fill used for project construction had 30% by volume of rock
rubble intermixed. Oysters have also colonized the shoreline areas where the rubble is
exposed. No oyster counts have been completed as yet, but visual observations suggest
significant coverage. Figure 8 are photos showing typical oyster recruitment.
Seagrass
Three species of seagrass occur in the project vicinity: Halophila decipiens, Halophila
johnsonii, and Halodule wrightii. H. johnsonii, listed as a threatened species, is the most
abundant on site as it is throughout the LWL. H. johnsonii was observed recruiting
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10. Figure 5. Aerial view of the completed project at lower low tide (July, 2005).
Figure 6. Before and after photos of mangrove planter (April 2005 and November 2007).
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11. Figure 7. Before and after photos of planted Spartina (April 2004 and August 2006).
Figure 8. Oyster recruitment to riprap and shoreline rubble.
to the newly placed fill even as construction and associated turbidity continued.
The first post-construction seagrass inventory was conducted during summer 2006. The
survey method involved visiting the site at the lowest of low tides and wading the
shoreline to a depth where the bottom was no longer visible. Wire survey flags were
placed around the edges of the observed grass beds, which were mapped using GPS to
sub-meter accuracy. This method proved effective for one-third to one-half of the
potential seagrass areas. The results of the 2006 survey show that H. johnsonii has
become established along the entire 1.2 mile length of the project, covering a total of 1.2
acres (0.5 hectares). Only a few small beds of H. decipiens were observed. Densities of
both species were high wherever they occurred.
A second survey was performed during summer 2007. Seagrass coverage had increased
by more than 10 times to 14.1 acres (5.7 hecrtares) (Figure 9). H. wrightii was observed
in at least two locations, and cover of H. decipiens was increasing. H. johnsonii still
represented roughly 90%-95% of the seagrass present.
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12. Figure 9. Snook Islands seagrass coverage, 2006-2007.
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13. Wildlife
Fish and wildlife usage of the project site increased dramatically after construction. Prior
to construction, there was a seawall with an immediate drop into an anoxic dredged hole.
Construction created a gradually sloping inter-tidal wetland shelf, and shallow submerged
areas recruiting seagrass. Wading birds, shorebirds, and ospreys regularly use the site as
feeding and resting areas. Schools of juvenile fish are swimming in the shallows and
around the Spartina at high tide. Manatees have also been observed feeding on the
Spartina. A pair of American oystercatchers (Haematopus palliatus), listed a Species of
Special Concern in Florida, appeared in 2004 and have been nesting each year on top of
the mangrove riprap wavebreak. They successfully fledged a chick in the summer of
2007.
Conclusion – Lessons Learned
The LWL has suffered extensive environmental damage from development. It has been
changed from a freshwater to an estuarine system, and dredging and filling eliminated the
littoral shelf that provided much of the biotic productivity in the system. Construction of
the Snook Islands project resulted in the successful creation of 10 acres of mangroves, 2.8
acres of Spartina marsh, 2.3 acres of oyster reef, and more than 14 acres of new seagrass
habitat with the potential for ~30 acres more. Addition of these submerged and shallow
sub-tidal resources to the LWL system resulted in increased fish and wildlife usage at the
project site.
Heavily degraded systems such as the LWL lack much of the biotic productivity of less
impacted systems. Radical environmental damage such as has occurred in the LWL can
only be mitigated by radical remediation. Projects such as this are necessary to offset the
historic loss of natural resources. It was anticipated that construction of this project would
be enthusiastically endorsed by the permitting agencies. That prospect was not realized.
This project provided an opportunity to add close to100 acres of inter-tidal and shallow
sub-tidal resources to the LWL. However, the permit application was recommended for
denial because of impacts to 0.25 acres (0.1 hectares) of sparse H. johnsonii that was
barely surviving on the narrow shelf between the seawall and the dredged hole. It took 2
years and application of significant political pressure to acquire environmental permits.
Regulatory agencies have an obligation to protect existing environmental resources;
however in severely degraded systems such as the LWL, a broader and more supportive
perspective is necessary in order to undo at least some of the damage that has been
wrought over the centuries. Hopefully, the documented success of this project will help
convince the regulatory agencies to re-evaluate their positions on future large scale
enhancement/restoration projects.
Acknowledgements
I would like to thank the project partners: City of Lake Worth, Florida Inland Navigation
District, U.S. Army Corps of Engineers, Florida Department of Environmental
Protection, and the West Palm Beach Fishing Club. I would also like to thank our
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14. contractor, J.E. McAmis, Inc., and in particular Scott Vandergrift and John McAmis, Jr.,
for their excellent work. Thanks also to Carman Vare, Reubin Bishop, Brock Stanaland
Carolyn Beisner, and Anne Matthews for their valuable assistance during construction.
References
Dames and Moore, Inc. 1991. Lake Worth Lagoon Natural Resources Inventory and
Resource Enhancement Study. Report for Palm Beach County Department of
Environmental Resources Management. December 15, 1991.
Palm Beach County Department of Environmental Resources Management and State of
Florida Department of Environmental Protection, Southeast District. 1998. Lake Worth
Lagoon Management Plan. August 1998. 257 pages.
Vines, William R., 1970. Surface Waters, Submerged Lands, and Waterfront Lands.
Report for the Area Planning Board of Palm Beach County. April, 1970
37