Seawall foam injection in Alabama: when it works and when it does not

Foam suits a sound wall whose only fault is a void. A sound wall has a straight line, tight joints and anchors that still hold.

• A small void under a walkway or cap slab.
• Settling soil behind a wall that has stopped moving.
• A gap that a contractor has traced to one failed joint, now sealed.

If the wall leans or the cap has split, foam only hides the sign. See the tiebacks and anchors page for those cases.

Foam is a poor choice when the soil keeps leaving. Fill a hole and the next tide can open it again. A wall with a broken panel, a missing tieback or a bad toe needs the cause fixed.

• The wall is leaning or bulging.
• Panels are cracked through or displaced.
• The base is scoured and the toe is exposed.
• Water is pouring out through joints at every tide.

In those cases the soil loss and drainage page and the repair or replace guide are better starting points.

A crew drills small holes through the cap or the soil and pumps foam under pressure. The foam expands to fill the gap and then cures hard. Good work is monitored so it does not lift or crack the slab.

1. Find the void with probes or a camera.
2. Seal the leak path that let soil out.
3. Inject in stages and watch for movement.
4. Recheck the area after the next high water.

• What caused the void, and how will you stop it coming back?
• Is the foam rated for use in salt or brackish water?
• Will you tell me if the wall needs anchors instead?
• What happens to the foam if the wall is later replaced?

Get the answers in writing. A contractor who dodges the first question is selling a patch.

No method works if the leak stays open. To find the leak, start with the soil loss and drainage page.

• The contractor never inspects the wall, only the hole.
• There is no talk of why the soil left.
• The price is given before any measurements.
• You are told foam will straighten a leaning wall.

A sound pitch starts with a wall inspection and ends with a plan to recheck. If a wall is leaning, go to the assessment page first.

Watch the area for a season. Re-measure any settling after the next heavy rain and the next high water. Keep photos with dates. If the surface drops again, the cause was not fixed, and the contractor should say so.

Also keep the invoice, the product name and a sketch of where the foam went. A later wall repair or sale will need those records. The maintenance plan page shows how to keep them.

It can. Repairing an existing, permitted structure may fit the maintenance permit of the U.S. Army Corps of Engineers (the Corps), called Nationwide Permit 3. That permit covers rehabilitation of a serviceable structure with minor changes. Corps Nationwide Permit 3

ADEM conditions that permit in the coastal area. The work cannot be in or near wetlands, grassbeds or natural oyster reefs, and it needs State Lands authorization. ADEM concurrence conditions

Local offices differ. In unincorporated Mobile County, almost any residential or commercial work needs a permit. Mobile County permits page Inside Mobile, a flood-zone parcel needs a development permit for repair. Build Mobile flood permit Call before drilling.

Sources: Build Mobile website Mobile County Inspection Services Dauphin Island Town Hall Baldwin County Building Department

No sourced price for foam injection in Alabama turned up in our research. The closest published figure is for soil stabilization, which national guides put at $120 to $270 per linear foot. ^[7] Treat that as a rough range and get written quotes. See the cost guide.

Look for a marine contractor, not a general paving or slab crew. Foam under a seawall cap has to cope with tides, salt water and moving soil. Ask for references on waterfront jobs, and confirm the license before you sign. The contractor check guide lists what to verify.

Water levels around the bay can swing hard. During Sally, one gauge fell to about 7 feet below the average low-tide level. NHC Sally report Big swings stress the ground behind a wall, so recheck a filled void after any major storm.

Where wakes scour a wall's base, as on Fowl River, a filled void can empty again. Fowl River plan Read the Fowl River guide and the Dog River guide for those shores.