City of Hollywood

North Lake Dredging Feasibility Study Project No.: BES-05-043

Purpose of the Study



Analyze aquatic habitat and segrass populations



Coordinate interagency permitting requirements



Develop dredging options, projected construction costs and potential external funding sources



Evaluate The Feasibility of Dredging North Lake

Benefits of Dredging

•

Improve Navigation

•

Enhance Water Quality

•

Improve marina operations

Aerial Vicinity Map

Sailors Point

Feasibility Assessment Components Permitting Geotechnical and Sediment Investigation North Lake Dredging Feasibility Economic Analysis Benthic Assessment

Benthic Assessment

Purpose and Methodology Benthic Assessment

Avoidance/Minimization/ Mitigation Survey Seagrass and other Threatened and Endangered Species. Divide Lake into transects 200 feet apart Diver swims along transect looking for threatened or endangered species

Benthic Assessment

Benthic Assessment

•

Significant Findings

No Johnson Seagrass Present, Limited to sparse Paddle Grass Colonies

Benthic Assessment

Benthic Assessment

Benthic Assessment Sparse Seagrass Colonies

Impact of Benthic Assessment Findings

• Dredging Area is Limited by Presence of Protected Benthic Species • Dredging Areas with Protected Benthic Resources (i.e. Paddle Grass/Seagrass) will Require Mitigation

Benthic Assessment

Geotechnical & Sediment Investigation

Geotechnical Investigation

Rock Recovery and Quality

Determine Characteristics of Rock Substrate

Geotech & Sediment Invest.

Rock substrate can be dredged Core #1 Core #4 Core #2 Core #3 Core #5 Core #6

Sediment Investigation

West Sample

N 26 00.929

W 80 07.786

East Sample

N 26 00.961

W 80 07.231

Geotech & Sediment Invest.

Sediment Sampling Locations

Geotech & Sediment Invest.

•

Sediment Investigation

Tidal Water Level Fluctuation

Navigation limited by water depth at low tide

Average Tidal Fluctuation - 2ft

7 foot draft standard depth maintained by City of Fort Lauderdale 7 foot draft accommodates personal and small water crafts 2’ 4.5’ Mean High Water Mean Low Water

Geotech & Sediment Invest.

• • •

Sediment Investigation Results

Initial assumed Lake contained thick sediment/silt layer Rock substrate must be removed to obtain 7 feet of draft.

Hydraulic Dredge Will Be Used To Remove Rock and Sediment

Sediment Thickness Map

Geotech & Sediment Invest.

Permitting

Permitting Requirements

“Fatal Flaw” Regulatory Analysis Coordination with agencies to address concerns regarding seagrass, dredging, and sediment Commenting agencies include U.S. Fish and Wildlife Service, NOAA/National Marine Fisheries Service and Florida Fish and Wildlife Conservation Commission

Permitting

Environmental Resource Permit (ERP) from FDEP Section 404/7 Permit from US Army Corps of Engineers (ACOE) Environmental Resource License from Broward County EPD

Permitting Interagency Meeting/Coordination

Key findings of 1/13/05 meeting attended by City of Hollywood and representatives from NMFS and Broward County EPD Additional seagrass surveys will be required for Johnson seagrass prior to permitting Avoidance/minimizations needs to be shown for areas where seagrass exists Dredging must create a system that is beneficial to the growth of seagrass Agencies recommended a project that improves navigation but minimizes seagrass impact, improves existing habitat, enhances flushing and expands the benthic system

Permitting

Permitting Meeting Results

• BCDEP, and NFMS indicated options that minimize environmental impact are preferred.

• • Mitigation will be required Options that impact the entire basin will not be permitted.

Economic Analysis

Economic Analysis Options for Dredging North Lake

• • • • Option 1 – Remove Sediment Only Option 2 – Dredge entire lake to 7 feet below mean low water (MLW) Option 3 – Dredge entire lake to 7 feet below MLW except for areas with seagrass Option 4 – Dredge 100 foot wide perimeter channel to 7 feet below MLW.

Option # 1 (Remove Sediment) Economic Analysis Option # 1 Remove Sediment Only North Lake, Hollywood, Florida

Option 2 (7ft Draft)

Economic Analysis Option # 2 7Ft. Draft – Entire Lake North Lake, Hollywood, Florida

Option 3 (7ft – No seagrass)

Economic Analysis Option # 3 7Ft. Draft Lake No Impact North Lake, Hollywood, Florida

Option 4 (100 ft. Channel)

Economic Analysis Option # 4 100’ Channel North Lake, Hollywood, Florida

Economic Analysis

Benefits Summary

Benefits Improves navigation Improves water quality Requires Mitigation Minimizes Environmental Impact Option 1   Option 2    Option 3    

Total Cost $ 9.9M

$ 19.7

M

$16.0M

Option 4    

$5.9 M