Update on Canal Restoration Demonstration Projects Prepared by Wendy Blondin, AMEC

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1 Update on Canal Restoration Demonstration Projects Prepared by Wendy Blondin, AMEC

2 Canal Water Quality Improvement Program A.The Canal Management Master Plan was completed in September 2013 which evaluated the water quality in all Keys canals. B.Monroe County initiated a restoration demonstration program by funding $5 Million for canal restorations in Unincorporated Monroe County. C.The Village of Islamorada funded $100,000 to join in the demonstration program. D.An objective process to select the demonstration canals was developed. 2

3 Demonstration Canal Selection Process A.Only canals with Poor Water Quality were selected B.Canal Management Master Plan Ranking utilized to prioritize canals for water quality improvements C. Selection Criteria Ease of Permitting Ease in Implementation D.Grouped Canals by Applicable Technology Weed barriers to minimize additional organic accumulation Removal of accumulated organics Culvert connections to facilitate flushing Pumping systems to facilitate flushing Backfilling to remove deep stagnant zones E. Stakeholder Meetings 3

4 Monroe County Board of County Commission Approval of Canals for Demonstration Funding Weed Vi Barriers Organic Removal Culvert Installation Pumping Backfilling 2 Same Canal 2 categories 3 4

5 Village of Islamorada Approval of Canals for Demonstration Funding Weed Barriers Vi Organic Removal Culvert Installation Pumping Backfilling 2 5

6 Related Grants & Timelines EPA: Water Quality and Seagrass Monitoring Grant $300,000 Awarded to FIU in September 2013 For all canals Pre-construction demonstration monitoring to determine baseline Post construction monitoring to determine results of project Was water quality restored? Limited time availability of funds 3 years 6

7 Weed Barriers Objective prevent seaweed from entering and being trapped in a canal Several Types Air curtain Diffuser disks placed across canal mouth near the bottom Compressor or blower placed on shore near mouth Combination air curtain and physical barriers Air curtain in center of canal for boat access Physical barriers on each side consisting of pilings with netting Swing weed gates 7

8 Ineffective and Effective Weed Barriers Canal #266 Canal #290 8

9 Organic Removal Objective remove organics accumulated in canals that are decaying and using up dissolved oxygen Conceptual Design Hydraulic Dredge Dewatering System examples Design for water quality discharge Geotubes or settling basins Polymer addition (tested Solve 426 and 164 already been permitted in the Keys) Land Disposal of Material - Reuse Test results #266 meet <SCTLs, #290 low level Arsenic and Copper could allow mixing with clean fill 9

10 Sediment Sampling for Physical and Chemical Characterization and Bathymetry Canal #266 Canal #290 10

11 Culvert Connections Objective increase natural tidal flushing; reduce seaweed entrapment in the dead ends of the canal Conceptual Design Concrete box or elliptical culverts Connect two dead end canals under a road (#472/#470) or add a second opening to a canal to connect to open water (#459 under a road, #277 across private property) Similar to other designs in the Keys - e.g. Little Torch 11

12 Pumping Systems Objective increase dissolved oxygen and decrease stagnation by pumping in clean bay water to dead ends of canals Conceptual Design Intakes wet wells with submersible in-line pumps placed just inside the canal headwalls with piping placed just outside canal mouth Discharges diffuser manifolds placed at multiple dead end fingers in canals, scour protection Powered by solar panels 12

13 Backfilling Objective backfill canals to an average depth of 8 feet mean low water elevation to reduce deep stagnation zones and increase dissolved oxygen Conceptual Design Clean fill staged on shore Earthmoving and mechanical equipment to place the material on a barge from the canal shoreline An excavator located on the barge will place the fill material into the canal system Phase work from end of canal out to mouth 13

14 Aerator Modification Combined with Air Curtain Installation Objective reduce seaweed loading as well as enhance an existing aerator system to increase dissolved oxygen Already existing permitted aerator system in Treasure Harbor Basin Diffusers to be added to front of canal as an air curtain to block entry of seaweed as well as back end of basin to increase dissolved oxygen 14

15 Aerator Diffusers 15

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