This study includes portions of two CERP Yellow Book Components and the Southeastern ENP area that focus on seepage management in western Miami-Dade County. Seepage management will improve the quantity, quality, timing and distribution of freshwater in ENP and Florida Bay; including:

Improve freshwater flow volumes, timing and seasonal hydroperiods to restore and re-establish ecological resilience of wetlands in ENP, WCA-3B and Pennsuco wetlands over the 50-year period of analysis from 2030 to 2080.

To address the problems identified in the study area, a total of 33 management measures were identified and discussed at various locations. The management measures were then screened to 25 management measures and then used to create a draft initial array of 13 alternatives.  Based on screening criteria, an initial array of 4 alternatives was selected. Of those, Alternative 13 was determined to be the Preliminary Tentatively Selected Plan because of the ability to provide benefits in both WCA-3B and ENP, better meeting the project objective.

Alternative 2 (green dashed line): Construction of a semi-confining seepage wall (24-30 inches thick) west of the L-30 levee between the S-337 and S-335 structures and L-30 operations changes to reduce groundwater seepage from WCA-3B.

Alternative 4 (pink dashed line): Construction of a semi-confining seepage wall (24-30 inches thick) in the L-30 levee crown between the S-337 and S-335 structures and L-30 operations changes to reduce groundwater seepage from WCA-3B.

Alternative 11 (yellow dashed line): Construction of a semi-confining seepage wall (24-30 inches thick) in the L-31S levee crown between the S-331 and S-177 structures and South Dade Conveyance System operations changes to reduce groundwater seepage from ENP.

Alternative 13 (pink and yellow dashed line): Construction of a semi-confining seepage wall (24-30 inches thick) in the L-30 levee crown and the L-31S levee crown with operations changes in the L-30 canal and South Dade Conveyance System to reduce groundwater seepage from WCA-3B and ENP.

The Team reviewed existing data on seepage rates and wetland degradation in the study area to identify optimal locations for wall location and length. Three factors for determining length and location of seepage walls in Alt 13 were used: 

• Existing data on seepage and transmissivities
• Minimize potential impacts to water supply and adjacent well fields 
• Tie-in with existing structures to optimize seepage wall function and potentially improve efficiency of existing structures 

Based on this analysis, two alternatives were developed.   

ALT13A - (Yellow dashed line) - Construction of two semi-confining seepage walls (24-30 inches thick) in the L-30 levee crown and one semi-confining seepage wall (24-30 inches thick) in the L-31S levee crown. The north L-30 seepage wall extends 5.6 miles south from S-337, selected based on observed high transmissivities and seepage volumes in existing modeling information. The south L-30 seepage wall extends 3.8 miles north from S-356, selected based on observed high transmissivities and seepage volumes in existing modeling information with consideration to minimize potential impacts on the Miami-Dade Northwest wellfield. The L-31S seepage wall begins 0.2 miles south of the S-200 and extends 11.9 miles north, selected based on observed high transmissivities and seepage volumes in existing modeling information with consideration to minimize potential impacts on the Florida Keys Aqueduct Authority well-field while helping to improve efficiency of the S-332 B, C, and D pump stations and expand south from the existing 8.5 SMA seepage wall. The seepage walls will tie-in to existing water control structures where applicable. Additionally, operations changes in the L-30 canal and South Dade Conveyance System will be used to optimize reduction of groundwater seepage from WCA-3B and ENP.  

ALT13B (Pink dashed line) - Construction of one semi-confining seepage wall (24-30 inches thick) in the L-30 levee crown and one semi-confining seepage wall (24-30 inches thick) in the L-31S levee crown. The L-30 seepage wall extends 3.8 miles north from S-356, selected based on observed higher transmissivities and seepage volumes in existing modeling information with consideration to minimize potential impacts on the Miami-Dade Northwest wellfield. The L-31 seepage wall begins 1.5 miles south of the S-332D and extends 7.3 miles north, selected based on observed high transmissivities and seepage volumes in existing modeling information with consideration to minimize potential impacts on the Florida Keys Aqueduct Authority well-field while helping to improve efficiency of the S-332 B, C, and D pump stations and promote flows toward Taylor Slough while leaving a “gap” for flow east between this new seepage wall and the existing 8.5 SMA seepage wall. The seepage walls will tie-in with existing water control structures where applicable. Additionally, operations changes in the L-30 canal and South Dade Conveyance System will be used to optimize reduction of groundwater seepage from WCA-3B and ENP.  

The Final array will include evaluation of a Bird Drive Basin precipitation driven recharge feature and the benefits it provides for meeting the Southern Everglades Project objective.

1. Why are only 2 instead of 8 Yellow Book components being studied in Southern Everglades?

The Southern Everglades feasibility study was originally conceptualized in response to the continued degradation of the Southern Coastal systems, as reported by science through prior RECOVER system status reports. Originally encompassing eight potential CERP components, the Southern Everglades Feasibility Study was refined to ensure accelerated delivery within a $3 million, three-year scope. Through collaborative leadership between the South Florida Water Management District and USACE Jacksonville District, a high-opportunity actionable element was selected for immediate feasibility study consideration. By incorporating a 35% mandatory design requirement into the feasibility study to lower cost risk during construction, this phased approach provides a path for earlier execution while maintaining strict alignment with long-term CERP restoration goals.

2. What is RAPID Planning and how will it be implemented in Southern Everglades?

The RAPID framework is a new USACE-wide planning process to be faster and more effective in delivering high-quality, authorizable water resource projects. RAPID stands for Risk-aligned, Informed, Proportional, Iterative, Decisive. The RAPID framework ensures we do the right level of engineering at the right time to support study decisions, deliver a quality project, and scale analyses to the decision at hand to preserve time and resources.

The Southern Everglades feasibility study will fully implement the RAPID framework. This includes two (2) “Decision Points” with the Vertical Team instead of the Milestones previously implemented (Alternatives Milestone, Tentatively Selected Plan, etc.). The Southern Everglades is the first feasibility study in the nation to undertake this new framework, and we thank all our partners for their patience as we take this opportunity to shape a relevant and robust future for our Civil Works Planning program.

3. Will Bird Drive Basin and Pennsuco Wetlands be included as part of Southern Everglades?

The Bird Drive and Pennsuco wetlands are important features of CERP component U and BB, respectively, and will be assessed during the planning process for benefits aligning with the study objectives. Implementation of engineered solutions within these two areas will be limited. These features may provide benefits only as precipitation driven recharge features.

4. How will impacts to water quality, threatened and endangered species, and agricultural resources be addressed in the Southern Everglades project?

Concerns regarding potential impacts to water quality, threatened and endangered species, and agricultural resources will be evaluated and addressed as part of the Integrated Project Implementation Report (PIR) and NEPA document. The PIR and NEPA process includes detailed environmental and technical review to assess potential project effects and ensure compliance with applicable federal and state requirements.