Bulkheads and Seawalls

The Difference between Bulkheads and Seawalls

For years different people and organizations have tried to differentiate the terminology between bulkheads and seawalls. As it turns out, in the world of Marine Construction, the two phrases can be used almost interchangeably.

When considering the barrier that comes between land and water, a retaining structure known as a Bulkhead or Seawall will prevent the erosion of the land or beach from falling in to the specific body of water.

For years the vertical structures (sheeting) that made up the bulkhead or seawall has been typically constructed with traditional materials such as pressure treated wood, concrete, steel, or piled up rocks know as rip rap. Though these materials can perform adequately for their intended sue, the problem occurs when considering the longevity of these products in harsh marine markets. Bulkheads and Seawalls have to be designed and built to withstand the rigors of the harshest marine environments.

The problem with pressure treated wood is the fact that even with harsh chemicals such as creosote or copper chromium arsenate (CCA) the pressure treated wood will inevitably succumb to the hunger of marine borers. As we continue to improve the quality of our waterways, most notably thanks to the Clean Water Act of 1972, chemically treated wood has become an increasingly less popular choice when choosing a material to be used in Seawall and Bulkhead construction.

Concrete sheet piling reinforced with steel rebar has traditionally been another popular choice when choosing a bulkhead or seawall material. Unfortunately, concrete is a porous material that allows water to penetrate its surface over time. Specifically when salt water eventually permeates concrete and gets to the steel rebar, the rebar will begin to rust and deteriorate. In this situation it becomes only a matter of time before the integrity of the rebar is compromise and the concrete will begin to crack and eventually crumble.

Steel sheet piling can be an adequate vertical barrier to achieve great heights. Historically this product has been used in seawall and bulkhead construction to achieve great wall heights for deep water marinas and shipping ports. Steel in salt water environments is generally epoxy coated which is applied to the raw steel to help delay the onset of rust and corrosion. However, during the installation process and throughout the performance life of the wall, the epoxy coating is inevitably scratched, scraped, or removed exposing the raw steel. Once this happens the rust process rapidly takes root, and the steel sheet pile seawall or bulkhead’s strength will be compromised.

Rip rap has long been considered the first “green” choice when considering a bulkhead or seawall material. Piled up rocks can help prevent land erosion from falling into a waterway. Unfortunately, the rocks do not provide a vertical separation. The rocks have to be piled on top of each other at an angle extending back into the property. Several feet of waterfront property will be lost to the large footprint of the piles up rocks. Additionally the rocks serve as a sponge for gathering trash and waste as it splashes up against the shoreline. If the rocks will be frequented by pedestrian or children the natural snake habitat that rip rap provide for can cause a dangerous waterfront solution.

In recent years the material of choice for the construction of bulkheads and seawalls has become vinyl and composite sheet piling. Vinyl Seawalls and vinyl bulkheads are manufactured using recycled or reclaimed rigid PVC. The best part about this material is that PVC has no natural enemies. Marine borers will not feast on your seawall, and rot, rust and corrosion become problems of the past. Historically as traditional materials begin to fail, new seawalls and bulkheads have been built out in front of the old. As this process continues waterways are becoming narrower as the footprint of the old and new seawall extend into the waterway. With vinyl and composite sheet piling becoming the first material being specified with an indefinite useful life, the problem of decreasing our waterway capacity can be considered a problem being solved. Vinyl sheet piling has proven to be cost effective, sometimes the same or just slightly more expensive than traditional materials.

Composite sheet piling has been successful in seawall and bulkhead construction for a number of reasons. As the impact and flexural strength numbers approach that of lighter gauge steel, taller walls can be achieved with synthetic materials that were once not though possible. Composites can be seen in everything from shovel and hammer handles to new aircraft construction materials. The benefit is the strength to weight ration where you can achieve tremendous strength without the need for steel and heavy metals. Additionally, with the proper marine grade resin system, composite sheet piling can expect extremely long life spans.

So, the bottom line is don’t get too caught up in trying to define the difference in bulkheads and seawalls. The biggest differentiator is typically the geographic area that you live. What might be a seawall in Florida may be called a bulkhead in New Jersey. The most important consideration in the last twenty years is the material used to construct your wall. Vinyl sheet piling and composite sheet piling seem to be the wave of the present and the future. You should jump on the band wagon, because I know we are! Visit Seawalls for more information.