January, 2007, the news media reported that an ice skater fell through the ice on Donner Lake and died. Now eight years later the news media is reporting two youths fell through the ice and one died. We always talk about water safety, boat safety, yet we don’t talk about ice safety other than stay off. I retired from the 210th Air Rescue Squadron, Anchorage Alaska, I went on to manage delivery vehicles and was certified as an emergency medical technician with training in swift and cold water rescue. It is common place in Alaska for most forms of transportation to be accomplished on frozen rivers and lakes. The native Alaskans have over thirty words just to describe the consistency of snow. They have almost as many words to describe ice. This knowledge is truly a matter of life and death for surviving in Alaska. Knowing the type of ice you’re on and what to do in an emergency is a matter of life and death. Every year as the winter approached the newspapers run a lengthy article on ice safety. The following document, which has been compiled from the US Army Corps of Engineers and the Cold Regions Research and Engineering Laboratory (CRREL), is always the basis for the newspaper articles. Preparation is the first order of a day on the ice and contains four areas for evaluation. Physical condition needs to be a top priority. One should be in reasonably good physical condition able to sustain extended periods of intense exertion in the event of an emergency. Being able to swim or stay afloat in the event you end up in the water is critical of survival. Proper clothing that provides protection from low air temperatures, wind, and precipitation while at the same time allowing you mobility is an excellent investment. Moreover, clothing that has flotation properties, or a personal flotation device (PFD) is a good choice. It is wise to keep in mind the possibility of falling through the ice. Hip boots or waders should never be worn. Equipment is the next consideration and includes items for testing and measuring the ice thickness, as well as items for rescue or self-rescue. In the first category are a heavy ice chisel, an ice drill or auger (manual or powered), a measuring tape or stick that can be hooked under the bottom edge of the ice in an auger hole, and possibly a perforated ladle for cleaning ice out of the auger holes. A rope or rescue throw bag containing a rope that floats are essential if you are to aid someone in the water. Or a fishermen’s ice rescue picks are great for self-rescue. They thread through your jacket sleeves like childrens mittens and are immediately available in an emergency for pulling yourself out of the water onto the ice. Having a set of common-sense procedures is probably the wisest thing one can do and the following procedures are taken from the CRREL Ice Engineering Information Exchange Bulletin: Never go out on an ice cover alone, and never go out on the ice if there is any question of its safety. While you are planning the outing, obtain the record of air temperature for the past several days and continue observing air temperatures while the ice will be used to support loads. Always let someone know of your plans and when you will return. When you arrive at the waters edge, visually survey the ice. Look for open water areas, and look for signs of recent changes in water levels: ice sloping down from the bank because the water dropped, or wet areas on the ice because the water rose and flooded areas of the ice that couldnt float because it was frozen to the bottom or the banks. (If the ice is snow-covered, look for wet areas in the snow.) Listen for loud cracks or booms coming from the ice. In a river this can mean the ice is about to break up or move; on a lake larger than several acres such noises may be harmless responses to thermal expansion and contraction. Look for an easy point of access to the ice, free of cracks or piled, broken ice. If you are taking a vehicle or other equipment onto the ice, go out on foot first. Vigorously probe ahead of yourself with the ice chisel. If the chisel ever goes through, carefully turn around and retrace your steps back to shore, and try again some other day. Near shore, listen for hollow sounds while probing. Ice sloping down from the bank may have air space underneath. This is not safe; ice must be floating on the water to support loads. After getting on the ice, others in the group should follow in the leaders steps, but stay at least 10 feet apart. Only after you have learned the characteristics of the ice cover should any vehicle be taken on the ice. Once on the ice it is time to ask several questions because there may be many variations in the structure, thickness, temperature, and strength of a floating freshwater ice sheet. How thick is the ice? This is determined by drilling holes with the drill or ice auger. The technique is to drill a hole and check the ice thickness every 150 feet or so along the intended path. This should be done more frequently if the ice thickness is quite variable. Note whether the ice in each hole is clear (sometimes called black ice) or white (due to air bubbles-sometimes called snow ice). Measure the thickness of both kinds. On rivers the ice thickness and quality can change a lot in a short distance; be particularly alert to variations in ice thickness due to bends, riffles or shallows, junctions with tributaries, etc. For both rivers and lakes, warm inflows from springs can create areas of thinner ice. The ice near shores can either be thinner (due to warm groundwater inflow or the insulating effect of drifted snow) or thicker (due to the candle-dipping effect of variable water levels). Measure the snow cover thickness on the ice cover; significant variations in thickness may mean highly variable ice thicknesses. How thick does it need to be? A simple formula to estimate the minimum ice thickness required to support a load is ( ). Where h is the ice thickness in inches and P is the load, or gross weight, in tons; or you can also use the tables below to determine the minimum thickness. Required Minimum Ice Description of Safe Moving Load Safe Moving Load 1-3/4 One person on skies 2 One person on foot or skates 3 One snowmobile 3 A group of people walking single file 7 A single passenger automobile 8 A 2-1/2 ton truck 9 A 3-1/2 ton truck 10 A 7 to 8 ton truck Minimum ice thickness required to support a load Ice Load Required Ice Thickness Distance Between Loads (tons) (inches) (feet) 0.1 2 17 1 4 34 2 6 48 3 7 58 4 8 67 5 9 75 10 13 106 20 18 149 30 22 183 40 26 211 Loads on Ice The equation and table are valid when the load (such as a person on foot, or a wheeled or tracked vehicle) is distributed over a reasonable area of a continuous ice sheet. The larger the load, the greater the area it should cover for the calculation to remain valid. The graphs are neither designed for large loads that are concentrated in relatively smaller areas, nor loads that are at or near the edge of a large opening in the ice. The table assumes clear, sound ice. If white, bubble-filled ice makes up part or all of the ice thickness then counts it as only half as much clear ice. Any recent large snowstorm creates a new load on the ice. If the new snow is heavy enough, the ice sheet will sag and its top surface will be submerged below the water level. Then water will flood the top of the ice sheet through cracks, saturating the lower layers of the snow. Until this slush is completely frozen, stay off the ice sheet. When the saturated snow becomes frozen, it is an added thickness of white ice. Contrary to what you would expect, a rapid, large air temperature drop makes an ice sheet brittle, and the ice may not be safe to use for 24 hours or more. If the air temperature has been above freezing for at least 6 of the past 24 hours multiply the load by 1.3 obtaining a larger minimum ice thickness to account for any possible weakening. If the air temperature stays above freezing for 24 hours or more, the ice starts losing strength; table no longer represent safe conditions. Stay off the ice! You are likely to encounter cracks in the ice. Cracks are either wet or dry. If they are dry and they do not penetrate the ice sheet, then they are not a concern. If they are wet, multiply the load by 2, before you use the equation to obtain the required minimum ice thickness. If you plan to leave a load on the ice for extended periods, usually more than two hours, multiply the load by 2, before you use the equation to find the required minimum ice thickness. SAFE OPERATIONS ON THE ICE COVER If using an enclosed vehicle, always drive with the windows or a door open for quick escape. If you drive across wet cracks, your path should be as close to perpendicular to them as possible, instead of parallel to them. A load deflects the ice slightly into a bowl shape. When you drive on floating ice, this moving bowl generates waves in the water. If the speed of the waves equals the vehicle speed, the ice-sheet deflection is increased and the ice is much more likely to break. The problem is more serious for thin ice and shallow water. In general you avoid this danger by driving below 15 mph. When there are two loads on the ice, the safe distance between them is about 100 times the ice thickness at the required minimum thickness. This is shown in the third column of the table. When the two loads are different, choose the spacing shown for the larger load. At ice thicknesses greater than the required minimum, this spacing can be reduced. A loaded ice sheet will creep, or deform, over a long period of time, without any additional load. If an ice sheet has to be loaded for a long period, drill a hole near the load. If the water begins to flood the ice through the hole, move the load immediately. Remember this if your vehicle ever becomes disabled: if left for a few days, it may break through the ice as a result of long-term creep. If an emergency does occur the following steps are essential: If you don’t have the proper equipment or training to reach the victim from a safe distance, then don’t! Emergency services will be recovering two victims not just one. First is to notify emergency services. Advise them of a cold water rescue and the exact location of the emergency; then, appoint a lookout to wave down and direct emergency responders. This will ensure that the proper personnel and resources are dispatched and the quickest response time possible. If you must get within fifteen to twenty feet of the ice edge, then distribute your body weight by lying prone on the ice. DO NOT STAND UP! Have yourself tethered, preferably to a second person. In case you fall through the ice you, can be pulled back. DO NOT approach the victim from the front!! They are in panic mode, and they are apt to grab you and use you as a flotation device. Approach the victim from behind. REMEMBER! The integrity of the ice has already been jeopardized with in feet of its edge and in many instances will break-off. Remember that it is your responsibility for your own safety on ice. When in doubt, stay off the ice!
Posted on: Sun, 11 Jan 2015 01:08:33 +0000
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