Snow removal

From FIS Freestyle wiki

Snow removal is the job of removing snow after a snowfall to make competition track and course safer. This is done by both individuals, course crews, and the ski area, with tools and different types of machines and powered equipment.

Les Contamines FRA removing the fences to clear 50cm of snow off the course.

New Snow is recently fallen snow in which the original form of the snow crystals is recognizable. It is also considered to be the amount of snow fallen within the previous 24 hours.

Snow density is relatively constant over an area, but depth may vary considerably. An efficient and relatively accurate estimate of SWE at a given area can be accomplished by making lots of depth measurements relative to the number of density measurements.

Snow scoop is a push type of large snow shovel adapted for faster and easier removal of snow, without the need for manual lifting. The scoop usually includes a stamped, one-piece metal / plastic body having a relatively lightweight, rigid construction which facilitates shearing of snow from the surface to be cleaned and the easy ejection of snow from the scoop.

Snow removal is the job of removing snow after a snowfall to make competition track and course safer. This is done by both individuals, course crews, and the ski area, with tools and different types of machines and powered equipment.

Removing snow from the race arena is not rocket science.

It can however, seem like rocket science if some key principles are not observed. Over a period of years, key strategies have been developed to streamline the whole snow removal process.

A snowblower is a motorized machine that takes the backbreaking work out of clearing large areas of snow. They are indispensable for clearing snow from areas where traffic is heavy. Roads, train lines and airport runways, as well as sidewalks, driveways, parking lots and have the snowblower to thank for keeping traffic moving.

[edit] Concept Snow density

Snow density is commonly given as the density relative to water ( ρs/ρw), or specific gravity, expressed as either a dimensionless proportion, or as a percentage. For example, if we have a snowpack with;

• an average depth of 1.0 m,
• with a density of 35%,
• SWE would be 1.0m x 0.35, or 0.35 m.

[edit] Snow Density Considerations

Snow Density: The amount of space between molecules or particles of any substance is what determines its density. Density is equal to the mass (or weight) of a substance divided by its volume (d=m/V).

The metric system was set up in such a way so that the density of water can be written as 1 gram per milliliter (1g/mL). One mililiter (mL) is also equal to one cubic centimeter. 'Water' is "pure precipitation." Snow, on the other hand, is mostly air.

The density of snow is related to the measure of the water in snow.

• Pure water density is around 1000 kg (or one tonne) per cubic metre or 62.4 lb per cubic foot.
• Pure ice is just slightly less dense than pure water at about 917 kg per cubic metre (that is why ice floats on a pond or in our drink).
• Snow on the other hand has less density because it contains more air in a given volume than the ice.
• Heavily compacted snow, called firn, can be nearly as dense as ice (around 910 kg per cubic metre)
• Newly fallen snow more typically weights in at 70 to 150 kg per cubic metre (4.4 to 9.4 lb/cubic foot), but this increases rapidly once snow is on the ground and it begins to compact due to wind, the addition of liquid water and its own weight.
• Typically winter snowpacks have a density of 200-300 kg per cubic metre (12.5-18.7 lb per cubic foot),
• Vary with the moisture content (SWE) of the snow and that can vary across climatic regions.

[edit] Strategy

Depending on the snow accumulation and snow density, there is a fair amount of strategic planning involved in snow removal operations. A small 1-inch snowfall accumulation can usually just be slipped off the course. A heavier 2-inch snowfall calls for some strategy.

A 12-inch snowfall requires serious strategy. The figures below will give some idea of the physical reality.

The average width of a downhill course is 40 yards. The figures below are based on a section of the course 40 yards wide by 100 yards long.

• Snowfall of 1 inch (.03 yards) 100yds x 40yds x .03yds = 120yds3 that is 120 cubic yards of snow. If that were in a berm 100 yards long and 1 yard wide the snow would pile 1.2 yards high.
• Snowfall of 2 inches (.06 yards) 100yds x 40yds x .06yds = 240yds3. That is 240 cubic yards of snow in a berm 100yards long and 1 yard wide the snow would pile 2.4 yards high.
• Snowfall of 12 inches (.33 yards) 100yds x 40yds x .33yds=1320yds3 that is 1320 cubic yards of snow. In a berm 100 yards long and 1 yard wide the snow would pile 6.6 yards high!

The following points are valid:

1. Remove snow in the area where you wish to put the snow from the race line. This is always the first objective. If you slip and shovel snow from the race line first, you have a huge berm just outside the line that cannot be moved. Therefore you must completely clear the areas outside the race line first.

This gives a clear and open space where you can move the snow on the racing line to.

1. Remove snow on the low line/bottom of the slope first. On any slope or traverse snow must first be removed from the lower areas of the slope. As above, this is required to allow space for snow from further up the slope to be pushed down. When clearing the low line always add 30-50% more area to clear.

You will need to clear a greater area than you think.

1. A major goal of snow removal is to limit the formation of unwanted snow berms. Points 1 and 2 help to limit the formation of berms. Once developed snow berms are very difficult to move with slippers and usually require machines or shoveling. Collecting snow in berms near the fences so blower cats can deal with them is part of the removal plan. A berm in the middle of the race arena is not desirable.
2. Move snow away from the racing line and into small spill zones, or use snow storage areas.

The spill zones can be a good area to store small amounts of snow. These are areas where athletes normally will never get into unless they have fallen and slid into them. It is possible if time is short, to move excess snow into these areas and pack it down, by either sidestepping or with a snow groomer. Likewise, these are areas where large amounts of snow can be moved to and dealt with by blower cats. There are also designated areas where snow can be stored. Check on your section map to locate these areas. After snow has been collected in these areas, it must be packed and smoothed down. No clumps, piles, or bumps should be left protruding from the surrounding snow.

1. Move only the snow you need to. During the morning rush to move snow it is important to identify the areas where snow does not have to be removed. These areas can be dealt with in the period after the day’s race. Encourage workers to remain clear of these areas.

[edit] Other Principles

Boot Packing The mechanical reworking of snow to harden it and to prevent depth hoar formation, usually by a large number of people walking up and down the slopes. This affects deeper layers than ski-cutting. This compresses any depth hoar which has formed and helps prevent its formation by decreasing pore space. Boot packing increases snow density and strength. This method is generally limited to small areas due to the manpower required.

People moving, means moving snow No matter how many or how few, every person who moves on the course, to some extent, moves snow.

More personnel and softer snow means more snow movement; harder snow means less snow movement.

A practical example of this is the formation of moguls on a ski run.

For this reason all worker movement inside the race arena must be carefully controlled. Worker routes and exits should be used as often as possible.

Any movement inside the race arena should be coordinated to assist the section leaders in completing their pre-race tasks, rather than disrupting their efforts.

[edit] Reference

1. Wikipedia See Snow removal [1]

[edit] Also see

• Job Descriptions:
• Mogul Course Check List
• Aerial Check List
• Course Preparation Crews
• Aerial Maintenance Crews
• Finish Area Maintenance Crews
• Snow Density
• Section Leader
• Air Bump Crew
• Fencing Crew
• Snow and Course Preparation
• Snow Water Equivalent

Return to Snow and Weather Glossary, Working with Snow, Freestyle Skiing