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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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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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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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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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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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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Figure 3. Snook Islands construction plan.

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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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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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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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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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Figure 9. Snook Islands seagrass coverage, 2006-2007.

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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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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