Soil leaves a waterfront property quietly. It goes out through the joints of the wall on falling tides, a little at a time, for years. The first visible sign is usually a depression in the lawn, a settled paver, or a patio slab that has started to tilt.
By then the void underground is normally larger than the hole at the surface, and often there are several — connected to each other and to the same leak path through the wall.
Diagram
What this repair actually does
Two distinct jobs, which is why the page has two names.
Void filling replaces the volume that has been removed, so the ground is solid again where it was hollow.
Soil stabilization improves the material that is still in place but has been loosened and weakened by years of water moving through it. A void is the obvious problem; disturbed, low-density soil around it is the one people miss. New fill placed on weakened ground settles, and then you are back where you started.
Done properly, the zone behind the wall ends up able to carry load again — which matters if there is a patio, a pool deck, a driveway or a structure anywhere near the top of the slope.
Diagram
Why topping up the lawn does not work
It is the most natural response in the world and it does two unhelpful things.
First, it does nothing about the mechanism. Soil is leaving through the wall. Fill poured in at the top is just more material queued up to leave through the same route. The hole comes back, usually bigger.
Second, loose fill dropped into a void does not restore bearing. The surface looks right and the ground underneath still cannot carry anything.
Owners who top up for a few seasons often arrive at a repair several times the size of the one they would have had at the start.
Sequence: seal, then fill
This is the part that decides whether the repair holds.
- Establish the extent. Where the voids are, how far they reach, and where water is moving through the wall. Part of a marine inspection.
- Seal the leak path — chemical grout injection closes the route through the wall.
- Fill the voids and stabilize the soil so the ground carries load again.
- Fix the drainage. If water is still being delivered to the back of the wall by downspouts, irrigation or grade falling the wrong way, the pressure that drove the original problem is still there.
- Restore the surface — grade and finish.
Skipping step 2 is the classic and expensive error. New material behind a wall that still leaks becomes the next thing the tide takes.
Where it applies
- Behind seawalls and bulkheads that have been losing soil through joints
- Under settled patios, pool decks, walkways and driveways near the water’s edge
- After storm surge has scoured material from behind a wall — see storm damage repair
- Around dock and boat lift foundations where the surrounding soil has been washed out
- As part of broader erosion control and shoreline stabilization
When it is not the answer
If the wall itself is structurally finished — rotated, tiebacks gone, embedment lost to scour — stabilizing the ground behind it is temporary by definition. The soil will stay put only as long as the wall does. In that case the conversation is about seawall replacement or bulkhead replacement, and we will tell you that rather than sell you the smaller job twice.
If you have depressions near your wall, call (904) 327-3931 or send us photos.
Frequently asked questions
Can I just fill the sinkhole with dirt myself?
How do you know how big the void is?
What is the difference between void filling and soil stabilization?
Will the sinkhole come back?
Last reviewed October 2026 by Barefoot Marine Construction. Permit requirements and agency rules change — confirm current requirements with the reviewing agency before you plan work.