Why Seawalls Are Failing in Apollo Beach and Mirabay

Many properties in Apollo Beach—particularly in Mirabay Subdivision—were developed using a marine-grade backfill material behind the seawalls. While intended for coastal construction, this material behaves very differently than native soil.

Here’s the problem:

During development, canals were either dug before or after seawall installation, and then the space behind the walls was backfilled with marine-grade fill. This material holds water and fine sediments, making it extremely prone to water retention.

The result?
That saturated backfill creates an unbalanced load:

• Excess hydrostatic pressure builds up behind the wall

• Lateral forces increase beyond design capacity

• Over time, walls begin to tilt, crack, or collapse

Even newly installed walls can fail prematurely if the drainage design doesn’t account for this unique soil condition.

This issue affects most of Mirabay, as well as other Apollo Beach canal-side properties, and is one of the leading causes of seawall and retaining wall failure in the area.

Engineering Solutions for Seawall & Retaining Wall Failure in Apollo Beach

Seawalls in Apollo Beach and the Mirabay community often fail because the marine-grade backfill used during development retains water differently than native soils. Once saturated, this material can exert lateral earth pressures exceeding 250–350 psf — far more than many residential seawalls were originally designed to resist. Combined with seasonal tides and storm surge, hydrostatic pressure can rise rapidly behind the wall, creating uplift and causing progressive leaning, cracking, or full structural collapse.

Foundation Masters LLC engineers and repairs seawalls and retaining walls by first performing a geotechnical assessment to evaluate backfill composition, water table depth (often just 3–5 feet below grade), and drainage performance. Our solutions may include deep vinyl sheet pile replacement, engineered weep/drainage systems that reduce hydrostatic buildup by over 80%, and structural reinforcement with carbon fiber and tie-back anchors rated to 60–120 kips. By addressing both soil and water pressure, we prevent premature wall failure and extend the service life of waterfront properties in Apollo Beach and Mirabay. Learn more about our engineered retaining wall and foundation solutions »