"Ultra-Aire"

There’s more than one way to protect marinas and private docks from ice damage

By Scott D. Sargent

Ice damage to docks, pilings and boats during the 2003 - 2004 winter season was extensive, as well as unexpected, in some parts of the country. During the previous winter season, many marinas and private docks experienced a short term of very cold temperatures. More recently, the 2004 - 2005 winter season was “unusually mild for the country as a whole, “according to Douglas LeComte of the National Weather Service Following a series of fairly mild winters, many dock owners erroneously think that ice protection isn’t needed. Worse yet, many marinas don’t provide ice damage protection to docks, while undergoing massive construction at their facilities - adding to the damage and unnecessary additional costs to their bottom line.

Keeping waters warm

The laws of physics state, among other things, that water changes density at 39 degrees Fahrenheit. At this temperature, the water does a sort of “flip-flop.” That means that warmer water sinks and colder water rises. As water temperature decreases, ice can form at the water’s surface, sending fish to seek the warmer waters on the bottom. It’s possible to take advantage of the flip-flop, combined with using a little agitation, to prevent icing during the winter.

One way to do this is with propeller-type deicers. When installed properly, propeller-type deicers bring warmer water from below and push it along the surface. This particular method works best in at least six feet of water. Although there are several ways owners can install propeller deicers to obtain maximum efficiency, most aren’t installed properly. Unfortunately, most owners install propeller deicers pointing straight up, which is understandable give the purpose of the device. However, this is incorrect. The unit should always be installed at a slight angle.

What happens when deicers are installed straight up? Let this one specific incident, be your guide. The owner installed a propeller deicer by hanging it in front of a float that was pushing water straight up. There was a large ice sculpture building up on the front edge of the float where water was spraying. Three sides of the float were completely frozen in.

The bubbler system

Another deicing option is bubbler deicing systems, which use low pressure, high volume air pumped through self weighted hoses which lie on the bottom The air escapes through slits or holes in the hose to bring warmer water to the surface. The bubbles create a small amount of agitation on the surface and, with the warmer water, keep a small area free of ice.

Bubbler systems range from the ¼ hp systems that can supply up to 150 feet of hose, to full marinas of any size. Manufacturers design systems based on number of feet of hose needed, which then calculates to minimum cubic feet per minute (CFM) of air. From this, it’s possible to size the blower. All systems should be tailored to each specific need with an expansion factor built in. Bubbler deicing systems can be designed to protect individual pilings or suround a whole dock or boat. Bubbler deicing systems work well in shallow water situations because the hoses can be completely out of the water at low tide and will continue to work as the tide returns. These systems are adaptable and can be used in very unusual and special situations.

Propeller or bubbler ?

So which system should a marina or private dock owner choose for deicing its docks? The answer is: “It depends….” There are advantages and disadvantages to both types of systems.

Propeller deicers work best in deeper water because they are less apt to get clogged with debris from the bottom. They can be timed to run for “X” number of hours on and “X” number of hours off, and they will clear away ice of any thickness. They can also be mounted securely to a dock or piling and aimed away from the structure to push floating ice away.

On the negative side, they do not work as well in shallow water, as they can get jammed with debris or stuck on the bottom. If they are too close to the surface, they will suck air down and not push out as much water. Bubbler deicing systems must come on slightly before freezing temperature and remain on until the temperature rises above freezing. If they are turned off during freezing temperatures, they won’t clear any ice that forms. Also, water in the feed lines above the water will freeze and block air to the hoses. Bubbler systems only clear ice around the structures they are designed to protect. They do not clear large open areas of water, which could be a hazard to skaters or ice boats, etc.

Bubbler deicing systems do not work well at depths of 15 feet or more. In fact, only hoses with holes, not slits, can work at this depth or deeper. The initial cost of a bubbler system is usually two to three times the cost of a propeller system, but the durability and dependability of the system will usually even out the difference over time.

Bubbler systems can be more specific in their application. Outlying or isolated pilings can be protected individually with piling loops that only bubble around the pilings. The hoses supplying air to the loops would be non-perforated, so less volume of air would be needed. Individual piling deicers can be used for pilings on floating docks to protect only the pilings. They are made of PVC and put a stream of bubbles on each side of the piling, which keeps it clear.

Marinas and small dock owners should be wary of selecting the least expensive system because it may not always give the protection the marina or small docks needs. Moreover, marinas and small dock owners must properly design, install, and maintain any deicing system if it is going to work at its designed capacity. Marina owners and operators, as well as small dock owners shouldn’t wait until everything is frozen to discover their deicing system isn’t doing the job.