Seawall foam injection.
Understand uses and limits.

What injection is meant to do

Injection pumps a resin through the wall or into the soil behind it to fill voids and seal leaking joints so backfill stops washing out. The U.S. Army Corps of Engineers’ grouting manual distinguishes the jobs: epoxy resins are often used to repair structural cracks because of their bond strength, while urethane and acrylic grouts are mainly used to control water infiltration or act as filler.

That distinction is the key question for a Jacksonville owner. Sealing a leak is not the same as restoring the strength of a cracked panel, a rotted timber bulkhead or a failed tieback.

EM 1110-2-3506, Grouting Technology (31 March 2017)

Not all polyurethanes behave the same

The Bureau of Reclamation’s concrete repair guide explains that water-activated hydrophilic resins can form a foam or gel depending on how much water they mix with and may shrink in dry conditions, while hydrophobic resins need little water. How much they expand depends on the formulation and how confined they are.

In Reclamation’s underwater lab tests, hydrophobic grouts injected underwater floated to the surface as they cured and did not fully seal cracks, while hydrophilic grouts sealed cracks but clouded the water. In a field demonstration, two grouts performed differently on the same canal. Ask which product is proposed, why it suits your wall and water, and how it will be contained.

Guide to Concrete Repair, Second Edition (2015) · Underwater Performance of a Hybrid Polymeric Repair Material to Seal Cracks in Concrete (DSO-2016-04) · Underwater Cure Polymeric Repairs to Seal Seepage Cracks (project 2398)

When injection may be a reasonable option

• The wall is plumb and the cap, panels or sheets are sound, but soil is escaping through joints or small gaps.
• Sinkholes behind the cap are recent and the cause has been traced.
• An engineer or experienced contractor has confirmed anchors and the toe are in good condition.

When injection is the wrong first step

• The wall is leaning, bowing or has moved outward.
• Timber bulkhead members are soft, rotted or attacked by marine borers.
• Panels are broken, rebar is exposed or the cap is split along its length.
• Tiebacks, deadmen or the toe have failed, or scour has undermined the base.

In these cases, injection may hide the symptom while the wall keeps failing. Start with an assessment and compare repair and replacement scopes.

Wood-Boring Marine and Estuarine Animals in Florida (SGEB-15)

Water-quality rules still apply

Florida limits turbidity to 29 NTU above natural background, and work under state exemptions must control turbidity and sedimentation. Cloudy water from injection near the wall is exactly what turbidity rules address. Ask how the contractor will contain material and monitor the water.

Rule 62-302.530, F.A.C. – Table: Surface Water Quality Criteria · Rule 62-330.050(9)(b)5., F.A.C.

Questions to ask before paying for injection

• What caused the soil loss, and how do you know?
• Which product will you use, and is it hydrophilic or hydrophobic?
• How will you keep resin out of the water and confirm the voids were filled?
• What happens if sinkholes return, and what does the warranty cover?
• Is this a stopgap before replacement, and if so, how long should it buy?