RADICAL DAMAGE CALLS FOR RADICAL REMEDIATION: THE   SNOOK ISLANDS ENVIRONMENTAL ENHANCEMENT       PROJECT, PALM BEACH COUN...
future habitat enhancement projects. One site identified in the plan was at the Lake WorthMunicipal Golf Course (LWGC) in ...
Study SiteLake Worth LagoonThe Snook Islands project site is located adjacent to the LWGC in the Lake WorthLagoon (LWL) in...
construction. These dredge and fill activities along the shoreline resulted in a steeplittoral profile, with elevations dr...
Snook Islands (LWGC)The first task was to remove exotic vegetation from approximately 5 acres (2 hectares) ofthe LWGC shor...
section with a winch along a four-point anchoring system, working from the shorelineout. The barge set up could fill appro...
Figure 3. Snook Islands construction plan.                   30
Figure 4. Fill offloading and grading operation.As each section was completed, smaller barges with long reach excavators f...
Approximately 12,000 smooth cordgrass (Spartina alterniflora) and 9,000 seashorepaspalum (Paspalum vaginatum) were planted...
Figure 5. Aerial view of the completed project at lower low tide (July, 2005).Figure 6. Before and after photos of mangrov...
Figure 7. Before and after photos of planted Spartina (April 2004 and August 2006).               Figure 8. Oyster recruit...
Figure 9. Snook Islands seagrass coverage, 2006-2007.                         35
WildlifeFish and wildlife usage of the project site increased dramatically after construction. Priorto construction, there...
contractor, J.E. McAmis, Inc., and in particular Scott Vandergrift and John McAmis, Jr.,for their excellent work. Thanks a...
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2008 restoration conference article

  1. 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 AbstractThe Lake Worth Lagoon in Palm Beach County, FL was previously a freshwater lake fedby water from the north and west. In the 1870’s, a permanent oceanic inlet wasestablished near Palm Beach converting the freshwater system to an estuarine system.Mangroves and other estuarine flora and fauna colonized the lagoon. Over the next 100years, however, dredging, filling and bulkhead construction eliminated roughly 80% ofthe mangrove fringe and much of the lagoon’s shallow water resources. In 1998, PalmBeach County ERM began planning a habitat enhancement project at the Lake WorthMunicipal Golf Course. Dredging and bulkheading of the shoreline to create the golfcourse 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 toplace fill in the water to reconstruct inter- and shallow sub-tidal wetland grades. PeanutIsland was a ready source of dredge spoil, and an island makeover was in the finalplanning stages. The Peanut Island makeover project included offloading 1.2 millioncubic yards of spoil. Over 1,560 barge loads of spoil were transported 10 miles toconstruct the Snook Islands environmental enhancement project, resulting in creation of10 acres of red mangroves, 2.8 acres of Spartina marsh, 2.3 acres of oyster reef, and ~50acres of seagrass recruitment area. Radical environmental damage can only be remediedthrough radical remediation projects. However, regulatory agencies are typicallyuncomfortable with the impacts associated with projects of this type and magnitude. Agoal of this project, now that it has been successfully completed, is to encourage theagencies to appreciate the environmental benefits of such projects. IntroductionOver the past century, the Lake Worth Lagoon has experienced a significant assault on itsnatural resources. Dredging and filling of inter- and sub-tidal resources and associatedseawall construction virtually eliminated fish and wildlife habitat in the lagoon. In aneffort to address this loss of biotic resources, Palm Beach County Department ofEnvironmental Resources Management (ERM) produced the Lake Worth Lagoon NaturalResources Inventory and Resource Enhancement Study (Dames and Moore, 1990). Thisstudy inventoried existing natural resources within the lagoon and evaluated potential 24
  2. 2. future habitat enhancement projects. One site identified in the plan was at the Lake WorthMunicipal Golf Course (LWGC) in the City of Lake Worth.Project planning for the LWGC site began in 1998. Typical past wetland enhancementwork involved excavation of upland spoil sites to wetland elevations. However, thistechnique for wetland enhancement would not work at the LWGC because the uplandswere reserved for golf play. It was then that the focus of the project moved offshore. Itbecame clear that the only way to produce a meaningful project was to re-fill the lagoonbottom next to the LWGC where it had been previously dredged in order to re-establishwetland depths and grades that would support productive biotic communities.At the same time, a project was being developed for Peanut Island, a dredge spoil storageisland located at the Lake Worth Inlet. Both recreational and environmental features wereto be constructed on the island. The island’s spoil storage was at capacity, and plans werebeing developed to offload spoil from the island. It was decided to combine the twoprojects, and use the offloaded spoil to re-create inter-tidal and shallow submergedwetland grades that had been eliminated during construction of the LWGC. The projectsite was ultimately named the Snook Islands enhancement site. A location and vicinitymap is shown in Figure 1. Figure 1. Snook Islands location map. 25
  3. 3. Study SiteLake Worth LagoonThe Snook Islands project site is located adjacent to the LWGC in the Lake WorthLagoon (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 locatednear the north end of the lagoon, and the South Lake Worth Inlet is located at thesouthern 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, theoffshore bars were sufficiently exposed to create a permanent barrier, completely cuttingoff the inshore lagoon from the sea. Its waters became entirely fresh and stood somewhatabove sea level, with its precise elevation depending on the wetness or dryness of theseason. (Vines, 1970). Several early attempts were made to create navigable inlets to theocean, and in 1877 a stable inlet was excavated. Immediately the lake and its biota beganto change to an estuarine lagoon system with a mangrove dominated shoreline. Alsoduring this decade developers began dredging and filling the wetland edges of LWL, anactivity that would continue into the 1970s. Inter- and shallow sub-tidal resources weredecimated. Presently, 47 marinas and hundreds of private docks are scattered along theshoreline. Approximately 65% of the lagoon shoreline is bulkheaded, while only about19% of the shoreline remains fringed by mangroves. (Palm Beach County ERM andFDEP, 1998).Peanut IslandPeanut Island was originally created in 1918 using the material excavated when the LakeWorth Inlet was created. First called Inlet Island, Peanut Island encompassed only tenacres (4.0 hectares). By 1923 the Port was using the island as a spoil storage site for themaintenance of the inlet and the Port shipping channel. The Port sold the northern half ofthe island in 1991 to the Florida Inland Navigation District (FIND) as a spoil storage sitefor Intracoastal Waterway maintenance dredging. (Palm Beach County ERM and FDEP,1998).Today, as a result of continued spoil deposition from maintenance dredging of the inletand the Intracoastal Waterway, Peanut Island comprises approximately 86 acres (34.8hectares). The primary use of the island will continue as a spoil storage site, but the PortAuthority and FIND have made the perimeter of the island available to the public as apark through a long-term arrangement with Palm Beach County. (Palm Beach CountyERM and FDEP, 1998).Lake Worth Golf CourseThe LWGC has approximately 1.2 linear miles (1.9 km) of shoreline along the westernshore of central LWL. The existing upland portions of the LWGC were created throughthe dredging and filling of inter- and sub-tidal wetland resources and associated bulkhead 26
  4. 4. construction. These dredge and fill activities along the shoreline resulted in a steeplittoral profile, with elevations dropping quickly from +4.0 feet referenced to the NationalGeodetic Vertical Datum of 1929 (NGVD) at the shoreline to -7.0 feet NGVD justoffshore. This steep grade minimized the area suitable for development of inter- andshallow sub-tidal resources such as mangroves, seagrasses, and oyster reefs. Mean HighWater at the site is +1.79 NGVD. Mean Low Water is -0.8 NGVD. Open water dredgeholes as deep as -23.0 NGVD existed prior to construction, and depths below -10.0NGVD were common. Just over one-half of the existing shoreline is fringed with threespecies of mangroves (red: Rhizophora mangle, black: Avicennia germinans, and white:Laguncularia racemosa), inter-mixed with exotic Australian pine (Casuarina sp.) andBrazilian pepper (Schinus terebinthifolius). The bulkhead has failed over time, leading toerosion of the shoreline from wind and wake-generated wave energy. Methods and MaterialsPeanut IslandConstruction of the project began in the summer of 2003. All vegetation (primarily exoticspecies) was removed from the spoil storage area on Peanut Island. Removal includedclearing, 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 throughoutthe Maritime Hammock portion of the Peanut Island project or used for slopestabilization in areas cleared of vegetation. The remaining vegetation was burned in an aircurtain incinerator.Excavation of the island began immediately upon completion of clearing. Hydraulicexcavators, trucks and scrapers were used to excavate the material and transport it to thestaging area on the southwest side of the island. Trucks placed the excavated material in ahopper which fed a conveyor system set-up for loading barges. The hopper mouth wasfitted 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 conveyorsystem used to load the material on hopper barges for transport to the Snook Islandsproject site. Once loaded, the barges were transported 10 miles south to the project sitefor offloading. A photo of the barge loading operation on Peanut Island is included inFigure 2.While the excavation and transport of material was taking place, other crews beganconstruction of the island’s public use facilities. This included construction of a newlevee containment system capable of holding 300,000 cu. yds. (229,366 cu. meters) ofspoil, 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. 27
  5. 5. Snook Islands (LWGC)The first task was to remove exotic vegetation from approximately 5 acres (2 hectares) ofthe LWGC shoreline. Once cleared, all shoreline armor (rip rap, concrete rubble, andcollapsed 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 anddeposited 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 projectconstruction. Figure 3 shows the construction plan. Over 1,560 barge loads of materialpassed under three drawbridges during construction. Once the barges reached the projectsite, the material barge tied up to two barges arranged in an L-shape. On one barge was aKomatsu PC 1800 specially outfitted with an 18 yard clamshell bucket, and on the other ahopper and conveyor system. The fill was offloaded by the clamshell bucket into thehopper/conveyor system, and was discharged over a radial telestacker, which wasremotely controlled from the conveyor barge.The project site was divided into 50X50 foot grid sections with predetermined fillquantities scheduled for each grid. Material quantities and placement were monitoredusing belt scales and GPS positioning software, and were continuously updated as fillingprogressed. As each fill section was completed, the barges were moved to the next 28
  6. 6. section with a winch along a four-point anchoring system, working from the shorelineout. The barge set up could fill approximately 250 linear feet of shoreline before theanchors needed to be pulled and reset for the next section. The radial and telescopicmovements of the conveyor system allowed precise placement of fill into the 50X50 footgrid sections. A photo of the offloading system is shown on Figure 4. 29
  7. 7. Figure 3. Snook Islands construction plan. 30
  8. 8. Figure 4. Fill offloading and grading operation.As each section was completed, smaller barges with long reach excavators followedbehind to ensure finish grades were within tolerances. All of the excavators used forfinish work were equipped with Trimble Site Vision ® GPS systems capable of attainingfinish grades to within +/- 2.0 cm.As filling progressed into deeper water, the fill load became too great to be supported bythe existing mud substrate. Fine sediments had accumulated in the dredge hole over theyears, 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 theoperation. The contractor compensated by overfilling the template and pushing the fillout 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 limestoneboulder riprap was used to create the oyster reefs and mangrove planting breakwaters.Oysters were already colonizing suitable substrate in the project vicinity at depthsbetween -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 aneffort to encourage additional oyster recruitment. The mangrove planting breakwaterswere constructed between -1.0 NGVD and +4.0 NGVD. 31
  9. 9. Approximately 12,000 smooth cordgrass (Spartina alterniflora) and 9,000 seashorepaspalum (Paspalum vaginatum) were planted 2 feet on center. The Spartina was plantedbetween 0.0 and +2.0 NGVD, and the Paspalum between +2.0 and +4.0 NGVD. Roughly50,000 red mangroves (Rhizophora mangle) were planted 3 feet on center on the 4offshore islands and on the three mangrove planters along the shoreline. The mangroveplanting shelf was constructed between +0.8 and +1.0 NGVD. Results and DiscussionThe project was completed in June 2005, and resulted in creation of 10 acres of redmangroves, 2.8 acres of Spartina marsh, 2.3 acres of oyster reef, and approximately 50acres of seagrass recruitment area. Project construction eliminated the original shorelinearmor along the golf course, and replaced it with a soft, vegetated shoreline. The offshoreislands and oyster reefs provided protection from wind and wave energy, stabilizing theformerly eroding shoreline. In 2004, Hurricanes Frances and Jeanne made landfall nearthe project site. Because the project was well underway, no damage was sustained to theproject or to the LWGC shoreline. Figure 5 shows an aerial view of the completedproject.Red mangrovesThe planted red mangroves achieved a survival rate of approximately 80% after twoyears. The mangroves were collected as propagules by volunteers and raised in a nurseryto the 6 to 8 leaf stage. They were then planted on 10 different occasions by volunteers asconstruction of the islands and shoreline planters was completed. Figure 6 shows typicalbefore and after photos of the planted mangroves.SpartinaThe 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 andafter photos of planted Spartina.OystersOysters (Crossastrea virginica) have colonized the oyster reefs and base of the mangroveplanting wave breaks. The fill used for project construction had 30% by volume of rockrubble intermixed. Oysters have also colonized the shoreline areas where the rubble isexposed. No oyster counts have been completed as yet, but visual observations suggestsignificant coverage. Figure 8 are photos showing typical oyster recruitment.SeagrassThree species of seagrass occur in the project vicinity: Halophila decipiens, Halophilajohnsonii, and Halodule wrightii. H. johnsonii, listed as a threatened species, is the mostabundant on site as it is throughout the LWL. H. johnsonii was observed recruiting 32
  10. 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). 33
  11. 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. Thesurvey method involved visiting the site at the lowest of low tides and wading theshoreline to a depth where the bottom was no longer visible. Wire survey flags wereplaced around the edges of the observed grass beds, which were mapped using GPS tosub-meter accuracy. This method proved effective for one-third to one-half of thepotential seagrass areas. The results of the 2006 survey show that H. johnsonii hasbecome established along the entire 1.2 mile length of the project, covering a total of 1.2acres (0.5 hectares). Only a few small beds of H. decipiens were observed. Densities ofboth species were high wherever they occurred.A second survey was performed during summer 2007. Seagrass coverage had increasedby more than 10 times to 14.1 acres (5.7 hecrtares) (Figure 9). H. wrightii was observedin at least two locations, and cover of H. decipiens was increasing. H. johnsonii stillrepresented roughly 90%-95% of the seagrass present. 34
  12. 12. Figure 9. Snook Islands seagrass coverage, 2006-2007. 35
  13. 13. WildlifeFish and wildlife usage of the project site increased dramatically after construction. Priorto 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 submergedareas recruiting seagrass. Wading birds, shorebirds, and ospreys regularly use the site asfeeding and resting areas. Schools of juvenile fish are swimming in the shallows andaround the Spartina at high tide. Manatees have also been observed feeding on theSpartina. A pair of American oystercatchers (Haematopus palliatus), listed a Species ofSpecial Concern in Florida, appeared in 2004 and have been nesting each year on top ofthe mangrove riprap wavebreak. They successfully fledged a chick in the summer of2007. Conclusion – Lessons LearnedThe LWL has suffered extensive environmental damage from development. It has beenchanged from a freshwater to an estuarine system, and dredging and filling eliminated thelittoral shelf that provided much of the biotic productivity in the system. Construction ofthe Snook Islands project resulted in the successful creation of 10 acres of mangroves, 2.8acres of Spartina marsh, 2.3 acres of oyster reef, and more than 14 acres of new seagrasshabitat with the potential for ~30 acres more. Addition of these submerged and shallowsub-tidal resources to the LWL system resulted in increased fish and wildlife usage at theproject site.Heavily degraded systems such as the LWL lack much of the biotic productivity of lessimpacted systems. Radical environmental damage such as has occurred in the LWL canonly be mitigated by radical remediation. Projects such as this are necessary to offset thehistoric loss of natural resources. It was anticipated that construction of this project wouldbe 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 shallowsub-tidal resources to the LWL. However, the permit application was recommended fordenial because of impacts to 0.25 acres (0.1 hectares) of sparse H. johnsonii that wasbarely surviving on the narrow shelf between the seawall and the dredged hole. It took 2years 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 supportiveperspective is necessary in order to undo at least some of the damage that has beenwrought over the centuries. Hopefully, the documented success of this project will helpconvince the regulatory agencies to re-evaluate their positions on future large scaleenhancement/restoration projects. AcknowledgementsI would like to thank the project partners: City of Lake Worth, Florida Inland NavigationDistrict, U.S. Army Corps of Engineers, Florida Department of EnvironmentalProtection, and the West Palm Beach Fishing Club. I would also like to thank our 36
  14. 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 StanalandCarolyn Beisner, and Anne Matthews for their valuable assistance during construction. ReferencesDames and Moore, Inc. 1991. Lake Worth Lagoon Natural Resources Inventory andResource Enhancement Study. Report for Palm Beach County Department ofEnvironmental Resources Management. December 15, 1991.Palm Beach County Department of Environmental Resources Management and State ofFlorida Department of Environmental Protection, Southeast District. 1998. Lake WorthLagoon 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

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