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 runs into the millions each year. Many private dock owners watch in frustration each year as the ice slowly tears their dock to pieces. There are three main docks for ice-damaged ships.
One way this happens is if the frozen surface of a body of water moves slowly with the wind or current. This may be imperceptibly slow, but there may be plenty of mass behind the movement, enough to crush a spring.
Another common problem is “Piling Jacking” which occurs when the water level changes. Ice forms around the pilings at low tide and then floats up when the water level rises, pulling the piling up from the bottom. When the water falls again, a new band of ice forms on the water line and the process is repeated.
The final source of damage occurs when loose slabs of floating ice, driven by wind or currents, collide with the pier. These rams don’t have to move very fast to deal a lot of damage.
The best way to prevent dock damage is to remove the dock from the water during the winter months. However, that is not always possible. Fortunately, there are a couple of options to help protect docks from ice. The first solution is called “Dock Bubbler”. Dock bubblers consist of a source of compressed air and a perforated pipe or hose that is secured to the bottom of the lake or river around the perimeter of the dock. If set up correctly, a bubbler will emit a curtain of bubbles causing the water to circulate. The bubbles will push warmer water from below to the surface, melting the ice.
The second option is to install a de-icer in the water. In-water de-icers, sometimes called marine or dock de-icers, have a submersible motor ranging from 1/4 HP to 1 HP driving a propeller. These units are suspended below the dock or from a float anchored just outside the dock. In-water deicers create a flow of water, again drawing warmer water from below the surface and directing it to the target surface area. If suspended vertically, a de-ier pier will create a roughly round area of clear ice. If they are suspended on an angel, they will clear an elliptical area. They need to clear an area larger than the pier, creating open water around the pilings or floating parts of the structure. In-water de-icers can be installed even after ice has formed, purchase by cutting a hole and suspending the unit. Under normal circumstances, ice will be removed from the target area within hours.
There are several popular brands of in-water de-icers that are readily available and vary in unit wattage, voltage, and cord length. The voltage will be determined by the power source available on 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 place your unit in water, but plug it into a dry ground fault interrupted power source or a suitable extension cord. The connection should be located where there is no danger of submersion. Typical cable lengths range from 25′ to 150′. The power of the unit is determined by your typical ice cleaning needs. A handy de-icer performance chart can help you decide what size unit you’ll need for your dock application.
As you can imagine, running one of these electric defrost options for months can add to your electric bill. Many dock owners install a special thermostat or timer that controls the operation of the bubbler or defroster. These units are located above the water and control power to the de-icer unit. The thermostats will turn on when the air temperature drops below a set point and turn off when the temperature rises above a set point. That means if the temperature rises above freezing for several days or so (or even during the afternoon), the defroster turns off and saves energy. Keep in mind that many thermostats are calibrated for freshwater or saltwater, so be sure to choose one that is appropriate for your application.
Timers work on a similar principle, allowing the defroster to run for several hours and then turn off for several hours. It may take some trial and error to determine the optimal timing sequence for your particular conditions.
While de-icers will protect against icing around a pier and can be used to form an open breakwater to prevent moving ice from crushing a pier, they will not protect against floating ice. In some areas, particularly rivers, large chunks of ice driven by current or wind can act like a battering ram, hitting piers. If you are faced with this hazard, you may need to set up protective pylons or floating booms to deflect moving ice away from the pier and shore-side structures.