In some parts of the country, ice can cause a lot of problems for dock owners. According to the boating industry publication “Trade Only”, this damage amounts to millions each year. Many private dock owners watch in frustration each year as ice slowly rips their dock to shreds. There are three main was ice damages boat docks.
One way this happens is if the frozen surface of a body of water slowly shifts with wind or current. This can be imperceptibly slow, but there can be a lot of mass behind the motion – Enough to crush a dock.
Another common problem is heave or “Piling Jacking” which occurs when water levels change. Ice forms around pilings during low water and then floats when the water levels rise, pulling the piling from the bottom. When the water drops again, a new band of ice forms at the water line and the process is repeated.
The final source of damage occurs when loose slabs of floating ice, driven by the wind or currents collide with the dock. These battering rams don’t have to be moving very fast to cause a lot of damage.
The best way to avoid dock damage is to remove the dock from the water during the winter months. However, that isn’t always possible. Fortunately, there are a couple options to help protect docks from ice. The first solution is called a “Dock Bubbler”. Dock bubblers consist of a compressed air source and perforated pipe or hose that is secured to the lake or river bottom around the perimeter of the dock. If set up correctly, a bubbler will emit a curtain of bubbles that will cause water circulation. The bubbles will push warmer water from below to the surface to the top, melting the ice.
The second option is to install an in-water de-icer. In-water de-icers, sometimes called dock or marine de-icers have a submersible motor ranging between 1/4 HP and 1 HP that drives a propeller. These units are suspended below the dock or from a float anchored just outside of the dock. In-water de-icers create a flow of water, again, pulling warmer water from below the surface and directing it at the target area of the surface. If suspended vertically, a dock de-ier will create a roughly round area of cleared ice. If suspended at an angel they will clear an elliptical area. They need to clear an area larger than the dock, forming open water around the pilings or floating portions of the structure. In-water de-icers can be installed even after ice forms, buy cutting a hole and suspending the unit. Under normal circumstances, the ice will be cleared from the target area in a matter of hours.
There are several popular brands of in-water de-icers that are readily available, and they vary in unit power, voltage and cord length. Voltage will be determined by the power source available at the dock. 110v is the most common, but many docks are equipped with 220v. You will need a cord long enough to allow you to position your unit in the water, but plug in to a dry ground-fault interrupted power source or suitable extension cord. The connection will need to be located where it is not in danger of being submerged. Typical cord lengths range from 25′ to as long as 150′. The power of the unit is determined by your typical ice clearing needs. A handy de-icer performance table can help you decide what size unit you’ll need for your dock application.
As you can imagine, running one of these electric de-icing options around the clock for months at a time can run up the electric bill. Many dock owners set up a special thermostat or timer that controls the operation of the bubbler or de-icer. These units are located above the water and control power to the de-icer unit. The thermostats will turn on when air temperature drops below a set point, and will turn off when the temperature rises above a set point. That means that if the temperature rises above freezing for several days, or (or even for the afternoon) the de-icer is shut down and saves power. Note that a lot of the thermostats are calibrated either for fresh water or salt water, so make sure you choose one that is appropriate for your application.
Timers work on a similar principal, allowing the deicer to work for several hours, then shut down for several hours. It may take a little trial and error to determine the optimal time sequence for your particular conditions.
While deicers will protect against ice forming around a dock, and can be used to form an open water break to keep the shifting ice from crushing a dock, it won’t protect against floating ice. In some areas, particularly on rivers, large chunks of ice propelled by the current or wind can act as a battering ram, pummeling docks. If you are faced with this danger, you may need to place protective pylons, or floating booms to deflect moving ice away from the dock and shore side structures.