Case Study – Vashon Island Seawall Stabilization

A residential waterfront property on Vashon Island, Washington, had soil loss behind a 10-inch concrete seawall along Puget Sound. The engineering drawings showed 3-6 inches of material loss, creating stability concerns. Ram Jack West performed SW-RP1 seawall repair foam injection, coordinating with Wolden Structural Engineering, and obtained permits through local authorities.

Initial Assessment

Field inspection documented voids and sunken grade behind the seawall. The site’s location in a King County area vulnerable to sea level rise necessitated environmental protection during construction.

Proposed Solution

SW-RP1 was selected for its ability to penetrate loose soils, expand upon contact with water, and create a watertight structural matrix behind the seawall. The material transforms the surrounding soil into an impermeable mass, preventing soil erosion and providing long-term stabilization. The repair plan included 20 injection points at 6-ft depth with corresponding 2.5-inch filters to manage future drainage and prevent the buildup of hydrostatic pressure.

Procedures

1. Obtained all necessary environmental permits and installed protective barriers along the shoreline before starting work.
2. Identified panel joints with soil loss, and prepared access 1 foot behind each joint.
3. Injected SW-RP1 deep into the soil to stabilize and fill voids, approximately 1 gallon per vertical foot.
4. Core-drilled panels at the water line at 5-foot intervals.
5. Placed 2.5-inch pressure control filters in each hole for hydrostatic relief.
6. Removed temporary controls and restored the site post-completion.

Results

The two-day project successfully stabilized soil behind the seawall and eliminated voids. Work was completed without in-water activities and minimal site disturbance. Compared to traditional seawall replacement, this approach achieved approximately 70-80% cost savings while providing permanent stabilization and eliminating the need for heavy excavation equipment.

Case Study – Poulsbo Historic Seawall Restoration

A historic waterfront residence in Poulsbo, Washington, required soil stabilization behind a 135-foot-long concrete seawall built in 1901. Wolden Structural Engineering identified voids behind the 5-foot-tall structure, indicating ongoing soil loss. The project utilized SW-RP1 seawall repair foam to restore stability without replacement.

Initial Assessment

Engineering evaluation documented vertical cracks along the seawall without structural offset, but revealed substantial voids behind the wall. The erosion hazard area designation and 100-year floodplain location required engineered solutions to prevent continued property loss.

Proposed Solution

The design specified expansive polyurethane injection to fill voids and bind soil particles. SW-RP1 was selected for its rapid-setting properties and resistance to water infiltration. The system included 2.5-inch filter drainage ports spaced 5 feet apart to relieve hydrostatic pressure.

Procedures

1. Established 26 injection locations at 5-ft intervals along the 135-ft seawall.
2. Injected approximately 170 gallons of SW-RP1 resin using controlled techniques.
3. Monitored placement to prevent wall crack extrusion.
4. Drilled access holes to 6.5-ft depth behind the structure.
5. Installed 30 pressure control filters with geotextile filtration media.
6. Completed surface restoration within permit requirements.

Results

The three-day stabilization project addressed soil loss while preserving the historic structure. Post-construction monitoring confirmed successful void filling throughout the treatment area. A cost analysis demonstrated approximately 70-80% savings compared to complete reconstruction, while extending the existing structure’s service life by decades and reducing construction duration compared to traditional methods.

Case Study – Soverel Harbour Marina Seawall and Walkway Stabilization

Soverel Harbour Marina, a 2,700-linear-foot marina in Palm Beach Gardens, Florida, had significant underwater erosion and soil loss beneath its seawall and walkway. This repair project was initiated due to severe underwater erosion, verified by divers, which threatened nearby structures. The job was completed by Seawall Repair Network® contractors Stable Soils.

Initial Assessment

The inspection revealed that the underwater erosion was severe enough to require immediate attention. The team faced unique challenges, including working around luxury yachts without disruption, managing potential material travel in the water, and mitigating settlement issues in pavers.

Proposed Solution

To address these issues, the team proposed a phased injection approach using SWR-RP1 single-component polyurethane. This solution aimed to stabilize the soil, prevent further erosion, and maintain marina functionality while working around luxury yachts.

Procedures

1. Install turbidity barriers to contain potential material release.
2. Inject one gallon of SWR-RP-1 per vertical foot, every 3 feet along the joints of the seawall.
3. Install 3-inch steel pressure control filters between seawall panels for future maintenance.
4. Remove and replace pavers as needed.
5. Compact the soil and restore the pavers post-injection.

Results

The project began with an initial 250-foot test section, which was completed successfully using 830 gallons of SWR-RP1. After 18 months of monitoring with no reported issues, the Stable Soils team received approval to treat the remaining sections of the marina. To date, 1,000 feet have been completed, with plans underway to complete the remaining section.

Case Study – Treasure Island Marina Seawall Stabilization

Treasure Island Marina contacted Panhandle Seawall & Infrastructure in early 2024 to address severe erosion behind 600 feet of seawall. Soil loss had destabilized the structure, causing adjacent concrete sidewalks to settle and create trip hazards for customers. The marina required a solution that would stabilize the seawall, eliminate safety risks, and avoid disruptions to daily operations.

Initial Assessment

Inspections revealed minor deflection in the seawall panels, which were structurally sound overall. However, soil probing identified significant voids and eroded areas behind the wall. A previous repair attempt using concrete pressure grouting had worsened the issue; cementitious material added excessive weight to the seawall and adhered to the underside of sidewalk sections, exacerbating settlement. The primary challenges included large voids beneath the sidewalk and ongoing hydrostatic pressure imbalances.

Proposed Solution

The repair plan combined three strategies to address both immediate and long-term concerns. First, SW-RP1, a single-component polyurethane grout, was injected to seal the base of the seawall panels, bonding remaining soil to the structure and preventing future erosion. Second, AP Lift 430, a two-component structural polyurethane foam, was injected to fill large voids under the sidewalk and gently re-level the settled sections. Finally, permeable pressure control filters were installed in the middle of each panel to equalize hydrostatic pressure, reducing soil migration.

Procedures

1. SW-RP1 Application:

• Injection points were drilled 1 foot behind the seawall, extending 1 foot below the mudline.
• Material was injected every 4 feet along the wall behind each joint, using approximately 1 gallon per vertical foot.
• Overcame challenges from existing concrete grout by drilling 40-inch holes to reach native soil.

2. AP 430 Void Filling:

• An injection grid was established at 4-foot intervals through the sidewalk.
• Controlled volume injections prioritized void filling before precise lifting with dial indicators.

3. Pressure Control Filters:

• Filters were installed between injection points from the water side to manage hydrostatic pressure.

Results

The first 300-foot phase, completed in May 2025, stabilized the seawall, eliminated trip hazards, and maintained marina operations throughout repairs. SW-RP1 created a waterproof bond between the wall and soil, while AP Lift 430 lifted settled sidewalks by filling voids. The procedure saved an estimated 70-80%, representing over $150,000 in savings for the marina (this does not include the opportunity costs of having the marina temporarily shut down). Post-repair inspections confirmed no further soil migration or settlement, and plans to continue the remaining 300 ft are underway.

Case Study – Rum Cove Marina Seawall Repair

Rum Cove Marina first contacted Seawall Repair Network® contractors Stable Soils around 2017, experiencing severe soil erosion behind their 1,250-foot seawall. The primary issue was water concentration from the parking lot creating a “pressure washer” effect that was washing away soil behind the seawall. This erosion threatened the stability of boat slip pedestals and the marina’s infrastructure.

Initial Assessment

The seawall showed no significant lean, but the soil loss was critical. The marina’s pedestals were falling over, and the concentrated water flow was causing extensive washout. The site required immediate stabilization to prevent further damage and prepare for new infrastructure installation.

Proposed Solution

AP Lift 475 was recommended to fill the voids underneath the walkway due to its high compressive strength. To prevent further erosion from the seawall, SW-RP-1 was utilized to keep the soil from washing away.

Procedures

1. Void Filling:

• Establish a grid pattern for injection points (typically 3 feet apart) underneath the walkway.
• Inject AP-475 two-part polyurethane at a controlled volume to fill void.
• Use dial indicators to ensure that there is no unwanted movement of the walkway or seawall.

2. Single-Component Injection:

• Positioning injection points 12 inches behind the seawall and 12 inches below the mud line (5.5 feet below the cap) every 6 feet.
• Install 1/2-inch plastic jet filters between injection points along the seawall.
• Inject one gallon per vertical foot at every injection point.
• Monitoring for indicators of success such as air bubbles on the water surface and mud displacement near injection sites.

Results

Stable Soils completed the project in September 2020. Since implementation, no further issues have been reported with the seawall. The marina owners were satisfied and subsequently contracted additional sectional seawall repairs.

Case Study – Halifax River Seawall Revitalization

A 20-year-old concrete seawall along the Halifax River in Ormond Beach, Florida, faced significant structural and aesthetic challenges. The seawall, stretching approximately 170 feet, had endured years of soil erosion and environmental stress. The client sought a repair solution to stabilize the structure and prevent further damage to nearby property features, including a pool deck and house foundation.

Initial Assessment

Upon inspection, several critical issues emerged. The seawall cap showed extensive cracks and spalling, compromising both its appearance and structural integrity. While soil erosion was evident throughout much of the seawall, severe erosion near the pool area caused noticeable subsidence of the pool deck. Some weep holes lacked filter fabric, allowing the soil to erode directly through the wall during rainfall. Without intervention, continued erosion would have led to costly repairs for the pool area and potential structural damage to the house.

Proposed Solution

The repair plan aimed to stabilize the seawall structurally and address aesthetic concerns. It involved installing helical tiebacks to provide lateral support and prevent further movement or overturning. Additionally, polyurethane injection was planned to fill voids and stabilize eroded areas. The seawall cap was to be reconstructed using hydraulic cement and new rebar to restore its structural integrity and appearance.

Procedures

1. Helical Tieback Installation:

• Tiebacks were installed at every other panel along the seawall.
• These tiebacks provided lateral support to prevent further movement or overturning.

2. SW-RP1 Seawall Repair Foam Injection:

• Injection points were spaced evenly between joints.
• Due to large voids caused by severe soil erosion, 6–7 gallons of SW-RP1 seawall repair foam were injected per vertical foot.
• The foam expanded to fill voids, stabilize soil, and seal cracks in the wall.

3. Cap Reconstruction:

• The damaged cap was removed and replaced with a new concrete cap reinforced with rebar.
• Hydraulic cement was used to bond panels securely together.

Results

The repairs successfully stabilized the seawall, preventing further soil erosion and structural damage. The pool deck showed no further signs of subsidence after repairs. The client expressed satisfaction with completing the project at approximately 25% of the cost of a full seawall replacement. This project demonstrates how targeted repairs using helical tiebacks and SW-RP1 injection can effectively restore a seawall’s integrity at a fraction of the cost of replacement, ensuring long-term durability while minimizing disruption to surrounding property features.

Case Study – Chesapeake Bay Bridge Seawall Repair

The Chesapeake Bay Bridge repair project focused on fixing a damaged seawall. Large cavities had formed beneath the splash wall, which protects the structure from waves. When the first contractor tried filling these voids by pouring concrete at the seawall’s base, the attempt failed, forcing engineers to develop an innovative solution. The project was initiated due to concerns about the structural integrity of the roadway and the potential for further damage.

Initial Assessment

Upon inspection, it was discovered that the base material used to seal the bottom of the panels had deteriorated, creating substantial voids underneath the splash wall. The riprap, consisting of boulder-sized rocks, extended 15-20 feet above the waterline, with the splash wall situated on top. The voids were significantly larger than initially anticipated, requiring a more extensive repair approach.

Proposed Solution

A two-part approach was recommended:

• Apply two-component polyurethane AP Fill 430 to structurally fill voids.
• Apply one-component repair material SW-RP1 to stabilize the wall and seal leaks.

This solution was reviewed and approved by the project engineers, ensuring compliance with all necessary standards and regulations.

Procedures

Void Filling:

1. Applied AP Fill 430 to seal and fill the massive voids.
2. Free-shot the product without using injection rods due to the size of the voids.
3. Utilized full drum sets and additional material to ensure complete filling.

Seawall Repair:

1. Drove ½” steel rods 1 ft behind each panel down to 1 foot below the mudline.
2. Applied SW-RP1 following standard seawall repair protocols.
3. Injected material approximately one foot back from the wall and one foot below the mudline.
4. Administered half a gallon per vertical foot.
5. Monitored for bubbles and mud displacement to confirm proper filling.

Results

The project was successful, effectively sealing the voids and repairing the seawall. The client was satisfied with the outcome, leading to additional work opportunities. Approximately 200 gallons of SW-RP1 were used for the Chesapeake Bay Bridge project. The repair has shown no signs of deterioration since its completion, and the client has requested further testing and application of the product for other sections of the bridge.

Case Study – Duke University Marine Lab Seawall Project

At Duke University Marine Lab in Beaufort, North Carolina, facility managers faced a critical challenge with their aging seawall structure. An assessment revealed serious issues with the 20-foot tall panels, including breaches between joints and undercutting at the base that threatened the wall’s stability. With the potential risk of structural collapse looming, a reliable and efficient repair solution became essential. Seawall Repair Network ® contractor Acelution was brought in to address these urgent concerns.

Proposed Solution

The team proposed a targeted repair approach using SW-RP1, a specialized polyurethane product. This solution was selected for several reasons…

• Deep penetration capabilities: The product could reach and seal deep cracks and voids.
• Versatility: It could address both the joint breaches and undercutting issues.
• Minimal disruption: The repair method would not require extensive excavation or replacement of the existing structure.
• Cost: The price of this solution is roughly 70-80% of the cost that it would take to replace the seawall.

Procedures

1. The crew used ½ inch steel probes to run down the entire length of the panels to 1 foot below the mud line.
2. Work was focused on specific areas identified by the facilities manager.
3. The product was injected at single points, with additional injection points spaced 10 feet apart.
4. Approximately ½ gallon of product was applied per vertical foot.
   While injecting, the crew monitored for telltale signs such as bubbles and mud displacement.
   The technicians treated multiple areas across the facility, adapting the approach as needed.

Results

The project was successful, with multiple areas treated, using between 5 and 10 gallons of product at each spot. In total, approximately 150 gallons of SW-RP1 were used for the Duke University Marine Lab project. The success of this project led to positive recommendations for future projects on the same site.