Understanding the Herbert Hoover Dike Rehabilitation Spillway, Plan 6 and EAA Storage Flow way Alternatives

Transcription

1 Understanding the Herbert Hoover Dike Rehabilitation Spillway, Plan 6 and EAA Storage Flow way Alternatives

2 HHD Rehabilitation Public safety is Corps highest priority Analysis of designs to address rehabilitation need is underway Analysis must cover the range of options Design based on lessons learned from New Orleans New design increases redundancy and resiliency Implementation strives to minimize impacts to individuals and communities

3 N 8 INDIAN PRAIRIE CANAL Okeechobee KISSIMMEE RIVER 5 OKEECHOBEE NUBBIN SLOUGH Martin 7 HHD Rehabilitation 6 Glades ST. LUCIE CANAL FISHEATING CREEK 4 MOOREHAVEN Reach Boundary Town/City Lake Okeechobee SAND CUT CALOOSAHATCHEE RIVER CLEWISTON LAKE HARBOR Hendry 2 PORT MAYACA SAND CUT CANAL POINT PAHOKEE BELLE GLADE SOUTH BAY 3 Palm Beach 1 Reaches in miles Project Priorities Reach 1, 2, 3 High

4 Herbert Hoover Dike Rehabilitation Conceptual Design Reach 1 CURRENTCOMPLETED ROW PROJECT ROW Seepage Berm Dike Seepage Berm Lake Fill Sands Peat Drain Swale Existing Toe Ditch Drain Swale Limestone Layers Sands NOT TO SCALE Cutoff Wall (type, depth, & loc TBD) Order of constructing the cutoff wall and seepage berm may vary based on risk reduction, availability of lands, funds and ability to issue construction contracts.

5 Reaches 2 and 3 Rehab Major Rehab Report (MRR) currently being prepared We must consider alternatives to proposed plan in our evaluations Several options under consideration Rehab similar to Reach 1 Fixed crest spillway

6 HHD Rehab Analysis Conceptual Spillway Alternative 2 mi long spillway set at Elevation mi of US Hwy 27 would have to elevated Very large Storm Water Treatment Area (STA) would be required for water treatment Possible relocation of sugar mill and other infrastructure Land acquisition and relocations downstream of flow way and STA Navigation dredging within Lake Okeechobee

7 HHD Rehabilitation Spillway Alternative Concept

8 Spillway Option Advantages Reduced need to rehab Herbert Hoover Dike avoids expensive rehab work Harmful discharges from Lake O to the estuaries greatly reduced

9 Disadvantages Spillway Option Total disruption of water management options and CERP by largely eliminating storage function of Lake O; over 2M acre feet of storage would be lost Low lake levels more common, lasting longer, and more severe. Low lake levels and reduced water storage increases risk of salt water contamination of drinking water. Requires acquisition of large area south of lake, relocation of many existing infrastructure facilities and additional dike construction to contain the southward flows. These would be built to handle water surges.

10 Spillway Option Other Disadvantages (continued) Very large STA required to protect/improve quality of water entering Everglades. 10 year storm: 140,000 acres 25 year storm: 650,000 acres STA would be a water consumer Potential HTRW issues within flow way and STA. Dredging of rim canal for navigation and access to lake during more frequent low water events may expose additional seepage paths in what is left of HHD.

11 Spillway vs. Plan 6 Concept Spillway for HHD Rehabilitation Purpose - evaluated as an option in lieu of rehab of HHD Plan 6 Concept Defined in Recon report for Comprehensive Everglades Restoration Plan as possible component for moving water south from Lake Was not included nor recommended in the Restudy report to Congress

12 HHD Rehabilitation Spillway Concept and Plan 6 Concept

13 Next Steps Northern Everglades program to address additional storage and water quality needs north of lake Will require re-exam of entire flow restoration process from north to south Analyze need for additional storage (eg. EAA Cell 2) and treatment south of lake as well as other alternatives for all potential flow paths needed to reconnect the system.