Island Feasibility Study Presentation for the Tampa Bay Regional - PowerPoint PPT Presentation

Weedon Island Feasibility Study Presentation for the Tampa Bay Regional Planning Council Agency on Bay Management – August 9, 2018

Project Background  SWFWMD / County Cooperative Funding Initiative  2012 Weedon Island Preserve Management Plan  Goals and Objectives  Habitat Restoration and Improvement  Hydrologic Preservation and Restoration  Exotic and Nuisance Species Management  Evaluate Habitat Restoration/Enhancement Projects  Existing and Proposed Site Conditions  Permitablitiy  Costs – Measurable Benefits

Weedon Island Preserve  3,190-acre preserve  Study area 1,100-acres  Mangrove forest habitat dominates the landscape  Maritime hammock  Salterns  Salt marsh  Scrubby flatwoods  Seagrass  Significant cultural and historical resources present  Shell middens  Domiciliary mounds  Sand burial mounds

Weedon Island Preserve  Mosquito Ditching in 1950’s 1958 1943 1970

Feasibility Study  Goals  Habitat Restoration and Improvement  Restore saltern, mangrove, and salt marsh communities  Improve habitats by removing upland spoil mounds and improving circulation  Natural resource management practices such as prescribed fire  Exotic and Invasive Species Management and Control  Reduce the extend and abundance of exotic and invasive plants  Hydrologic Preservation and Restoration  Improve hydrology to improve water quality and circulation

Feasibility Study  Objectives  Increase Wetland Habitat Area  Improve Native Wetland Plant Communities  Removal of upland spoil mounds  Nuisance species removal  Hydrology improvements  Decrease nuisance species cover in both upland and wetland habitats by various methods of control  Identify project approaches that will not adversely affect cultural and historical resources within the study area

Feasibility Study  Constraints  Significant Cultural and Historical Resources  Access Issues  Cover type  Distance from uplands or open water  Lack of survey  Permit Complexity  Performance Criteria  Public Involvement

Restoration and Enhancement Approach  Spoil Mound Removal  Nuisance Species Removal  Focused, complete effort in larger areas of nuisance species  Selectively remove scattered nuisance species  Hydrology Improvements  Improve flushing and natural tidal regimes

Study Units  Based on changes in community and natural features  Allow assessment of:  Access restrictions  Cultural Resources  Permit complexity  Low, moderate, or high ranking assigned

Study Units Spoil Mound Removal

Study Units Nuisance Species Removal

Study Units Hydrology Improvements

Study Units Fire Units

Spoil Mound Removal - Hydroblasting  The process of moving soil with pressurized water  Portable water pumps  Specialized hoses  Blast mounds of spoil  Direct resulting slurry into existing mosquito ditches  Requires removal of nuisance species prior to Hydroblasting  Follow-up recommended  Grade lowered to that of surrounding wetland  Methodology yields mixed results  Amount of material removed  Elevation achieved  Type of soil remaining

Photo courtesy of SWFWMD

Cost Estimate (by Unit Acreage) Unit ID Unit Acreage Unit Access Restrictions Cultural Resources Permit Complexity Spoil Mound North Spoil Mound Removal Study Units SMR-1 2.62 $19,925 Low Low Low SMR-2 25.18 $191,494 Low Low Low Removal - SMR-3 8.94 $67,989 Low Low Low SMR-4 5.91 $44,946 Low Moderate/Low Moderate Hydroblasting SMR-5 8.02 $90,225 Moderate High High SMR-6 6.89 $52,398 Low High High SMR-7 6.49 $146,025 High High High SMR-8 12.35 $138,938 Moderate Low Low  Per Mound SMR-9 17.24 $193,950 Moderate Low Moderate SMR-10 11.27 $253,575 High High High  Low - $1,690 SMR-11 20.51 $155,979 Low High High SMR-12 43.23 $328,764 Low High High  Mid - $2,500 South Spoil Mound Removal Study Units SMR-13 15.34 $268,327 Low Low Low SMR-14 12.62 $220,749 Low Low Low  High - $5,000 SMR-15 18.62 $481,793 Moderate Moderate/Low Low/Moderate SMR-16 17.09 $298,938 Low Moderate/Low Low/Moderate  Estimated SMR-17 16.30 $421,763 Moderate Moderate/Low Moderate SMR-18 12.47 $645,323 High Low Moderate/High  Mound Size SMR-19 18.63 $325,876 Low Low Moderate SMR-20 18.15 $469,631 Moderate Low High  Number per Acre SMR-21 16.00 $414,000 Moderate Low High SMR-22 15.68 $405,720 Moderate Low High  419 Acres SMR-23 14.09 $729,158 High Low High SMR-24 13.90 $719,325 High Low High  $8.93 M SMR-25 20.61 $533,284 Moderate Low High SMR-26 13.93 $720,878 High Low High SMR-27 13.74 $355,523 Moderate Low Moderate  $21,310 per Acre SMR-28 13.39 $234,218 Low Low Moderate TOTALS 419.21 $8,928,710

Spoil Mound Removal – WIDO  “Walk In, Dig Out” (WIDO)  Includes temporary access roads (Walk In)  Spoil mound removal to create the temporary fill  Crane mats to reduce the amount of fill used  Temporary pipes to maintain flow

Spoil Mound Removal – WIDO  “Walk In, Dig Out” (WIDO)  Longer-term temporary access roads  Removed in phases

Spoil Mound Removal – WIDO  Long reach, amphibious excavators  Spoil used to selectively fill mosquito ditches  Or, hauled away

Spoil Mound Removal – WIDO  Dig the access road out (Dig Out)  Removal of remaining spoil mounds  Restoration of temporarily- impacted mangrove habitat  Fill backwater ditches  Hydrology Improvements  Improve Diurnal Flow  Deeper-water Refugia

Table 4-3 Sample Work Area Existing Conditions Spoil Mound Size Cover Type Square Feet Acreage % Removal - 83,457 Spoil Mounds 1.9 13.0% 381,517 Black Mangroves 8.8 59.4% Red Mangroves/Mosquito Ditches 177,000 4.1 27.6% WIDO 641,974 TOTAL AREA 14.7 100% Temporary Impact Quantities Size Work Area Square Feet Acreage % Access Road Impacts (fill) 74,620 1.7 11.6% Mosquito Ditch Impacts (fill) 7,172 0.2 1.1% Mosquito Ditch Impacts (dredge) 170,527 3.9 26.6% TOTAL TEMPORARY IMPACTS 252,319 5.8 39.3% Proposed Conditions Size Cover Type Square Feet Acreage % Black Mangroves Not Impacted 306,198 Restored Black Mangrove Temporary Impacts 74,620 Removed Spoil Mounds 64,022 Black Mangroves (Total) 444,840 10.2 69.3% Red Mangroves/Mosquito Ditches Restored 129,360 3.0 20.2% Deeper Water Refugia 41,167 0.9 6.4% Saltern/High Marsh 26,607 0.6 4.1% TOTAL AREA 641,974 14.7 100.0%

WIDO Results  Restored temporary impacts  Filled backwater ditches  Removed all nuisance species’ habitat  Hydrology Improvements  Improved diurnal flow  Created refugia

Table B-2 Equipment Cost Estimate Amphibious Excavator Spoil Mound Cost Type Cost Rate Type Cost per month 42,000 rental rate Removal - Manhours 10,000 160 hours, $25 / hr, 2.5 multiplier Fuel 3,500 50 gal/day @$3.50/gal WIDO Maintenance 4,200 10% rental rate Total Cost $ 59,700 Off-Road Articulating Truck Cost Type Cost Rate Type Cost per month 10,000 rental rate manhours 6,000 160 hours, $15 / hr, 2.5 multiplier Fuel 1,680 24 gal/day @$3.50/gal Maint 1,000 10% rental rate Total Cost $ 18,680 Front-end loader Cost Type Cost Rate Type Cost per month 2,315 rental rate manhours 6,000 160 hours, $15 / hr, 2.5 multiplier Fuel 1,680 24 gal/day @$3.50/gal Maint 232 10% rental rate Total Cost $ 10,227 Foreman Cost Rate Type Total Cost $ 10,000 160 hours, $25 / hr, 2.5 multiplier

Table B-3 WIDO Cost Estimate Equipment Plus Labor Cost Type Cost Spoil Mound Amphibious Excavator 59,700 Truck 18,680 Front-end Loader 10,227 Removal – Foreman 10,000 $ 98,607 per month $ 4,930 per day WIDO Construction Time Cost Type Days Cost Comment Main Access Road 1.1 5,423 1000 feet per day Spur Access Road 4.8 23,666 720 feet per day Long Reach Spoil Removal 12.0 59,164 6 mounds per day Fill Ditch 1.5 7,395 240 feet per day Dredge Ditch 3.9 19,228 350 feet per day Dig Out 4.8 23,666 720 feet per day removal TOTAL 28.1 $ 138,542 Incidentals (Reusable) Cost Type Quantity Cost temporary pipe 140 2,800 crane mats 10 5,000 $ 7,800 TOTAL Other Cost Type Quantity Cost Erosion Control 10% $ 14,634 Overhead 30% $ 43,903 Mobilization 10% $ 14,634 Contingency 10% $ 13,197 $ 86,368 TOTAL $ 232,710 PER ACRE $ 15,831