Title: PowerPoint Presentation
Author: Catherine Olnick

Blue Lake Phase 2
Shoreline Stabilization Plan
Tuesday, August 25, 2026

Key Team Members

STOKES
PATTERSON, EI

JORDON
CHEIFET, PE

Project Engineer

Project Director and
Coastal Engineering Lead

Goals

Create a Shoreline Stabilization Plan
Creation of a shoreline stabilization plan with recommended solutions for each section of shoreline based on cost, aesthetic, constructability, CDD feedback, and monitoring

Develop Shoreline Stabilization Alternatives
Identify viable shoreline stabilization solutions to protect each criteria of shoreline against toe scour, shelf erosion, seawall overloading from wind and wave
conditions (where exposed)

Characterize the Existing Shoreline and Retaining Wall
Create a series of criteria to characterize the Phase 2 shoreline in terms of shoreline exposure (Immediate Action, Future Action, Monitor)

Conduct a Site Inspection
Conduct a site visit to inform existing shoreline conditions including topography, existing retaining wall condition, shelf width, exposure to wind and wave conditions

Process

Shoreline and Retaining Wall Criteria and Categorization
Create three criteria to characterize the shoreline based on exposure to wind and wave conditions, littoral shelf limitations, and the condition of the existing retaining wall
Protected, Vulnerable, Vulnerable (Narrow)

Shoreline Stabilization Alternatives

Shoreline Stabilization Plan

Site Visit

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Develop a series of
effective shoreline stabilization options for each criteria of shoreline.
Perform a qualitative assessment of the pros/cons, evaluate effectiveness, and provide a rough order or magnitude cost

Provide
recommendations for each stretch of shoreline
Provide recommendations for monitoring Provide recommendations for maintenance Provide recommendations for inspections

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Observe existing
shoreline topography, bathymetry, retaining wall condition, littoral shelf limitations, existing docks, vegetation, and surrounding land uses house-by-house Photograph and GPS

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Retaining Wall Condition
Assessment

The retaining wall was observed to be “intact and plumb” or “intact but undulated”
Location-specific defects

Retaining wall “intact and plumb”

Failed tie-rod
Small crack in wall
Loose tieback anchor plate Loose tie-back anchor
Sheets cut at the mudline with a void underneath

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Retaining wall “intact but undulated”

Retaining Wall Condition
Assessment

“Intact and Plumb” approximately
7,800 LF
“Intact but Undulated”
approximately 4,100 LF
No large-scale repairs to the existing retaining wall are anticipated
Minor repairs should be addressed during Phase 2

Fetch Analysis and Exposure

Determine areas of wind-wave exposure and estimated wave heights

Potential Hurricane Tracks

Fetch Analysis

Estimated wave heights of up to 1.56’ across Project Area
Wave height limited by water depth “depth limited”
Water depth with 1’ of surge assumed at 19.3’ NAVD (C.E.)
Water depth lowered due to conversations with residents/CDD claiming depths 2-3’ lower than usual

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Shoreline Condition and
Exposure Criteria

Vulnerable – exposed to wind and wave action with retaining wall intact – requires protection (~7500 LF)
Sheltered – not anticipated to be impacted by future storms – needs little to no protection (~3200 LF)
Vulnerable (Narrow Shelf) – still exposed to wind/waves with wall intact but have a narrow shelf (less than 15’ – limits alternatives) (~1200 LF)

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Shoreline Failure

Seawall Failure

Shoreline Failure

Erosion & Toe Scour

Seawall Failure

Sheltered (3 Alternatives)

Existing Conditions – Leaving shoreline
as-is (minimal protection)
Shoreline Plantings – Provide limited erosion protection (Provide a level of service (LOS) of less than 5 years).
Concrete Erosion Control Mats – Small pre-cast concrete units embedded into a geogrid mesh. Provide erosion and scour protection but variable wave protection. Installed landward of the retaining wall (10 – 15 year LOS*).

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Shoreline Plantings

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Concrete Erosion Control Mats (FlexMat)

Sheltered (3 Alternatives)

Existing Conditions – Leaving shoreline as-is (least protection)
Shoreline Plantings – Provide minimal erosion protection (Provide a level of service (LOS) of <5 years).
Concrete Erosion Control Mats – Small pre-cast concrete units embedded into a geogrid mesh. Provide erosion and scour protection but variable wave protection. Installed landward of the retaining wall (10 – 15 Year LOS*).

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Concrete Erosion Control Mats (FlexMat)

Anchor for Concrete Erosion Control Mats

Vulnerable (7 Alternatives)

Existing Conditions – leaving shoreline as-is (least protection)
Articulated Concrete Block Mats (ACB) – Heavy, pre-fabricated concrete block mats strung together by cables. Provide a high level of erosion, scour, and wave action. Installed waterward of retaining wall (50-Year LOS*).
Marine Mattresses – Polymer mesh filled with bedding stone installed landward of retaining wall. Provide a high level of erosion and scour protection (50-Year LOS*).

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Open-Celled ACBs – vegetation can be installed

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Marine Mattresses – vegetation will not develop

Vulnerable (7 Alternatives)

Rock Revetment – Multiple layers of armor stone installed waterward of retaining wall. Provides a high level of protection against erosion, scour, and withstands wave action. Unrestrained. 50-Year LOS*
Toe Stones – Thin layer of armor stone installed directly in front of retaining wall. Provides protection against scour. Erosion protection limited by small footprint. Unrestrained. 50-Year LOS*

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Rock Revetment

Retaining Wall with Toe Stones

Vulnerable (7 Alternatives)

6. Rock Revetment with Marine Mattresses – Highest level of protection against erosion, scour, and wave action. Phase 1 design. 50-Year LOS.
7. Metal Mattresses – Steel mesh filled with smaller stones to form a mattress. Provide a high level of protection against erosion, scour, and withstand wave action. Installed waterward of retaining wall. 50-Year LOS*

Rock Revetment with Marine Mattresses

Metal Mattresses – Vegetation can be Incorporated

Vulnerable (Narrow Shelf) (4 Alternatives)
Shelf is less than 15’ wide (limited
footprint)
1. Existing Conditions – Leaving shoreline as-is (least protection)
2. Vinyl Retaining Wall – Demolition of the existing wall and installing new, more robust wall. Designed for erosion, scour, and wave action. 50-Year LOS.

Existing Conditions (Narrow Shelf)

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Longer Sheets
Longer Tie Backs (e.g., helicals) Stronger Cap (e.g., concrete)

Vinyl Retaining Wall

Vulnerable (Narrow Shelf) (4 Alternatives)
3. Rock Revetment with Marine Mattresses and Rock Apron (Phase 1 Design) – Demolition of the existing wall with landward installation of armor stones, marine mattresses, and rock apron. 50-Year LOS.

Rock Revetment with Marine Mattresses and Rock Apron

4. Metal Mattresses – Demolition of the existing wall with landward installation of metal mattresses. 50-Year LOS.

Metal Mattresses – vegetation can be installed

Breakdown of Options

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Rough Order of Magnitude Cost-Estimate Per Linear Foot of Alternative

Maintenance & Enhancement
Plan Recommendations

Sheltered – Shoreline plantings to provide a degree of erosion protection where not significantly impacted by waves.
Vulnerable – Metal mattresses to provide erosion and scour protection from waves. Incorporate vegetation.
Adaptable.
Vulnerable (Narrow) – Rock revetment with marine mattresses and rock apron (Phase 1). Demolition of existing retaining wall with landward installation. Provides erosion and scour protection and withstands wave action.

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Metal Mattresses – vegetation can be installed

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Rock Revetment with Marine Mattresses and Rock Apron

Maintenance & Enhancement
Plan Recommendations

Sheltered – Shoreline Plantings
(~3200 LF of shoreline)
Vulnerable – Metal Mattresses (~7500 LF of shoreline)
Vulnerable (Narrow Shelf) – Rock Revetment with Marine Mattresses and Rock Apron with Demolition of Existing Retaining Wall (~1200 LF of Shoreline)
Total Recommended Costs -
$2.54M – $4.25M
Cost per LF – $215-$355/LF

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*Costs for material and install only. Mobilization, demolition, environmental compliance, layout/as-built surveys, and other associated soft costs (e.g., permitting, design, construction oversight) are not included.
*Final quantities and unit costs may vary as the design is refined

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Cummins Cederberg Additional
Recommendations
1. Establishment of an Annual Monitoring Plan to Evaluate Potential Shoreline Change ($25,000 – $50,000 Annually Estimated)

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Similar style to FDEP Beach Monitoring conducted since the 1970s to provide representative cross-sections
Use of LiDAR to provide full coverage of shelf
topography
Installing metal pipe into the existing shelf and monitoring changes visually (no cost anticipated)
Surveys recommended to be conducted annually, biannually, or after storm events
Recommended for data to be reviewed by a coastal engineer and presented in a Physical Monitoring Report to summarize shoreline position and volumetric changes over time to identify changes and potential recommended actions.

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Cummins Cederberg Additional
Recommendations
2. Develop a Planned Waterfront Inspection Assessment Program to Periodically Assess the Condition of Shoreline Protection Elements ($5,000-
$10,000 each inspection)

No more than every 5-6 years (per ASCE MOP 130 for low-salinity conditions, after a severe coastal storm, vessel impact, or other atypical event
Frequency may need to increase based on element conditions

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Questions?