Snow grooming

Introduction

The main reason for grooming is to make the snow consistant and safe to ski, jump and board on. For competitions there are special requirements and details that demand extra knowledge and skills.

The general snow preparation is done with the same basic machines for all the snow disciplines. The 200 – 500 horsepower grooming machines are from 2.5 – 7 meters (8 – 22 feet) wide. Good driving routines are important since every hour in a machine is expensive (labour, fuel, fluids, parts, maintenance, etc). The basic grooming is, in normal conditions, done by using mainly the front blade and the tiller.

Front: The front blade is controlled by a hydraulic system. It is used to push snow around, clear out bumps and dumps, create even downhills and courses such that the surface is re-established after heavy use or snowfall (or established initially after snowmaking) 



Tiller (rear): The tiller is the most important piece of equipment for grooming, and will create a more consistant and compact surface by altering the distribution and size of the snow crystals. Speed, down pressure, angle and direction of the tiller (forwards, backwards) are adjusted according to the nature of the snow at the moment of grooming. 

For ski jumps and alpine hills, it is also often necessarry to use a winch. 

The winch is used when moving snow or grooming on steep hills where it is required, for safety, to anchor the machine’s winch cable to a winch anchor point at the top of the hill. When grooming using the winch-cat it is important to drive very slow such that the snow becomes as compact as possible. 

The fuel/diesel cost for a grooming machine is between 10 – 25 liters per hour, depending on the size of the machine. As in other industries, electric models as well as models fueled with hydrogen (See “News” section) are also now available.

Currently, fully electric model large grooming machines can operate for 2.5 – 3 hours (both Pistenbully and Prinoth). The Finish model EV snowmobile in the photo has a 9.5 kwH capacity and can drive 40 km before needing recharge.

The special and detailed grooming requirements for each of the snow disciplines are covered in the chapters below. Some of the disciplines require special attachments (see photos below of front mounted snow blower and snow bucket, and rear mounted track setter).

Snow density

The density of the snow varies a great deal between cold new snow and old compressed snow. Cold, dry new snow (powder snow) may have a density as low as 100 kg/m³, while snow that has partially melted, frozed again and been compressed can have a density of 500 – 550 kg/m³. Grooming machines will (usually) increase the density, and provide better ski conditions. For optimal competition conditions in Cross-Country, Biathlon and Ski Jumping, the density should be around 450 kg/m³, for snowboard ca. 530-550 kg/m³ and for alpine ca. 530 – 620 kg/m³ (depending on the competition event). When both recreational and competitive alpine skiers share the same course, the density should be reduced a bit.

1

Cross-Country/Biathlon

Base preparation

Summer

Base preparation is done both summer and winter, and both are important for the final product. Preparation of the courses during the summer is especially important where the snow conditions are marginal. The ground surface should be smooth enough that light grooming machines (snow mobiles, ATV with tracks or a grooming machine with “summer tracks”) can pack the snow as soon as a few centimeters cover the ground.   The ground surface will naturally vary, but short or cut grass may be the very best goundcover for a ski trail.  

Drainage is also very important, especially ditches along the trail towards higher terrain or slopes.  In long downhills it is important to put diagonal water bars to avoid erosion when rainwater runs long stretches down the trail.

Winter

After the first natural precipitation, the snow should be packed to a 10 – 15 cm deep and hard base layer.  It is important to get the air out of the snow by using a roller, drag og similar attachments (see photos). The first base grooming/packing is often done using ATVs or snowmobiles. 

General ski trails (with video examples)

Ski trails are groomed all over the World (both indoors and outdoors), and are used by all levels of skiers, from recreational beginner skiers to Olympic athletes. To increase the level of competency for the local associations, municipalities and venues that groom trails in Norway, the Norwegian Ski Federation and the “Association for the promotion of skiiing, Holmenkollen” created a National trail grooming manual (in Norwegian only) including educational videos. The manual covers the main topics of:  

• Machine basics 
• Safety and safety education 
• Grooming for Cross-Country 

The trail grooming manual covers grooming for both recreational trails and competition courses (see excerpts regarding classical track setting below) and includes videos with practical guidance in:  

• Packing the trail/course 
• Classical track setting
• Using the front blade 
• Buiding a “snow row” 
• Using the tiller

Methods and equipment for competition grooming

Grooming for competitions require specific knowledge and experience, and is performed following detailed requirements from the responsible event organizer. The snow conditions at different venues are hardly ever the same, so the local groomers’ knowledge of the snow conditions is perhaps the most useful tool.  However, a few general rules might be useful:  

Timing 

Since the snow takes time to “set up” after grooming, it is almost always best to groom well in advance of the first skiers.   For recreational trails it may not matter so much if the snow is soft and freshly groomed when the venue opens, but for competition courses a firm snow surface is always best:

• When the skies are clear or no precipitation is forecasted, groom during the evening or night prior to the competition (always groom when the temperature is falling, such that the snow and track firms up/hardens better)
• If snow or rain is forecasted the night or morning prior to the competition, wait as long as possible with the grooming. However, finish at least a couple of hours prior to the course opening time such that the snow surface and classical tracks firm up/harden.  
• Avoid grooming during the day and when skiing goes on. Close the whole or parts of the courses (if necessary) in the morning prior to when the competition warm-up and testing start. This may avoid soft conditions and sugar snow due to heavy use.

Use of tracks, front blade and tiller 

Most Cross-Country and Biathon venues use large grooming machines. The width of the machines vary from 2.5 – 7 meters, but they all provide similar results if advice from experienced groomers are followed. 

• Use the machine tracks to compress the snow across the entire course width (“edge to edge” as well as in the middle) such that the surface is evenly firm across (don’t drive the same alignment every day).
  
  
• After heavy rain it is sometimes good to drive without using the tiller (“open” up the snow to let it dry out faster).  
• During heavy snowfall it is best to groom for every 15 – 20 cm of new snow (gives good compression and makes further grooming easier). It is important to use the tiller on high speed such that the large new snow crystals are broken up and can compress/compact better
• When enough snow, use the front blade to push snow towards the middle of the course (the course should be a bit higher in the middle part)
• During clear and warm days with wet snow and cold nights (when snow freezes) it is best to groom close to the time when the freezing starts in the late afternoon (some of the water in the snow has then evaporated which might reduce icy conditions in the morning)
• In icy and hard snow conditions, using the tiller in reverse on the first grooming pass may give better results
• 12 – 14 km per hour is the recommended grooming speed in good snow conditions. 

Grooming with snowmobile

If the snow is not too icy, it is sometimes advantagous to groom both for classical and skating using snowmobile/ATV and attachments (such as Ginzugroomer or equivalent that lightly scrapes, renews the surface and/or sets new classical tracks). In addition to less operating/fuel costs, the snow is then spared the wear and tear that frequent heavy grooming causes. The desireable snow crystals and snow quality may be prolonged, and sugar snow avoided.

Even in big Championships the courses are somtimes groomed using snowmobiles and attachments.

• The best example of clever snowmobile grooming is the 2015 Biathlon World Championship in Kontiolahti. The courses were exclusively groomed with snowmobile and Ginzugroomer/rollers the enire duration (the snow was dry and cold).

Setting of classical tracks for training and competitions

For skating (free technique) we normally do not set classical tracks (not even on the edge of the course in downhills). The competition jury may change this in certain cases, especially for long, straight downhill sections. For individual start competitions in classical technique, one classical ideal line track is normally set. For mass-start or for multiple lap competitions with many participants, the jury may likely decide to set more classical tracks (depending on the available course width).  When setting three or four tracks (in mass-start competitions) using a large machine with a quad track pan will give the best result.

Ideal line track in classical technique is defined as: The track is set such that it is the most natural and shortest path for the skier to follow. This means that the track cuts in towards the inside of corners. When using two classical track the track setter uses the same approach.

Removing classical tracks in corners:

Setting the track will depend on the snow conditions and the assumed speed of the skier. In downhills with corners the classical tracks are removed where the person setting the track (the track setter) or jury believe it is too difficult to stay in the tracks. In sharp corners in other places (flat terrain or uphill) the classical tracks are removed or not set such that the skier can change direction easier (pushing off with the outside ski). For high level competitions it is required to mark the start and stop of these “free zones”.  

To remove or not set track in the correct places requires some experience. It may be smart to discuss this with some of the skiers and coaches the day prior to the competition. A “rule of thumb” is that it is better to remove too much than too little. Often the locations of the “starts and stops” are marked as a visual tool for the groomer or track setter.

Width of courses and the tracks:

A normal adult skier needs about 1.5 meter width when skiing in classical technique (half of this is for the pole plants). This means that it should be approximatelly 1.5 meter between each skier (measured from the centerline of each person) where there are multiple tracks. In the start area for a mass-start, or otherwise in narrow courses, the distance can be 1.25 meter. There are also standards for the distance and depth of the actual grooves comprising the classical tracks.

• It should be ca. 22 cm between the right and left ski or groove (measured from the middle of the ski).
• Each of the grooves should have the following shape:
  • 13 cm wide on the snow surface and 5-6 cm on the bottom. 
  • The depth is 5 cm

Track setting for competitions:

• In general, the track should be set at the nearly coldest time of the night and when the temperature is still falling.  
• When the weather changes from wet & warm to cold: Wait until some of the humidity has evaporated and the snow starts to dry up (otherwise it will be very icy the next morning) 
• When the weather changes from cold to wet & warm: The track should be set when it is still cold, or as early as possible prior to the first skiers (for it to harden and stay firm longer).
• At zero degrees Celsius and new snow: If possible, the track should be set close to the competition’s start-time (it will firm up fast with the humid snow)  
• When falling snow: The track should be set close to the competition’s start-time. An experienced track setter would be able to drive the machine and the track setting attachment directly over the old tracks. During snowfall forerunners are also required to ski in the tracks prior to the start of the competition.  

Trails for recreational use 

Trails for recreational use should be groomed for both classical and free techniquer (skate) skiing. Proper and safe track setting for classical technique will depend on the available width.

If the course is 4 – 5 meter wide, one classical track is set on one side of the course, 50-70 cm from the edge such that there is space for the poles.

If the course is wider than 5 meters, two classical tracks can be set. These should be set in parallel together on one half of the course, or one on each side of the course. In both cases, it should be a 3 meter space for skating. All lit trails, and most training- and recreational trails should be groomed this way.

Removal of tracks: 

The classical track should be removed in sharp corners and in curvy downhills also for recreational trails. For recreational trails, it might be smart to remove tracks even in straight downhills to make it easier to snow plough. It is better to remove the classical track more than too little. A recreational skier needs more time to get into and out of the classical track while maintaining good balance, even on flat terrain. Often it is beneficial if the person driving the grooming machine skis the trail him/herself to gain personal knowledge of the appropriate track setting in changing snow conditions and on the up- and downhills.  

Mixing the snow layers 

Sooner or later, all venues and courses will be experiencing icy conditions. With a frequent melting/freezing cyclus (often typical at late winter or spring time) a renovator can be used to create better conditions. A front renovator is quick mounted on the machine (exchanged with the front blade) and can mix the snow down to 30 cm depth.   

• Frequent use of the renovator can delay the formation of icy conditions by mixing old and new snow  
• By using the renovator after new snowfall, the new snow can be mixed with the old snow layer, and create a smooth high quality surface that will last much longer  
• Old, colder snow closer to the ground can be mixed with the wet- or slurry like snow during warm days and nights. If this is done early in the evening, the mixture will freeze better and faster, and give a much better surface the next morning.  
• During icy condition, a renovator can reduce the grooming time by 50%!

2

Alpine

Base grooming of alpine slopes

Grooming of alpine slopes are described in details in the Norwegian Ski Federation’s manual published in 2014 (in Norwegian only).  The manual’s general advice is repeated here:  

After the first major snowstorm(s) leaving 15 – 30 cm snow on the ground, it is common to pack the snow to establish a base layer. It is important to not use the large grooming machine too early since it will then likely mix grass and small rocks into the snow. When using the machine the first time, it is important to be very careful if using the tiller. Keep the tiller depth at a minimum with as little down pressure as possible. On steep dowhills it is important to not drag the snow down to the bottom.   

It is important to ensure a good base layer before allowing the large grooming machine onto the slopes. Too early access may cause long lasting damage to both the snow and the machine.

Grooming in different conditions 

How to best groom in different conditions depends on experience and expertise. Several variables also influence the driving.

• visibility  
• depth of snow  
• snow consistency  
• temperature  
• gradient of the slope  
• hardness of the surface (if icy or not) 

Following are a few principles for how to approach different snow types and conditions:  

Dozing artificial snow

Grooming artificial/man-made snow already starts when planning the snow production. Producing the right amount of snow in the right location is essential for end result when dozing and distributing the snow.  

The snow should be produced higher up the slope such that it can be dozed or pushed downhill or diagonally downhill to its planned location. If the produced snow is a bit wet, it should dry out for 1 – 2 days before being distributed. Man-made snow is “expensive”, so be careful and distribute evenly. This may be challenging if the slope is long, the produced snow piles large and the ground uneven. Normally the snow is distributed 40 – 60 cm deep, but sometimes deeper in places where the wear and tear is high.

Modern grooming machines have GPS sensors and equipment that read the terrain and are very helpful when controlling the depth during dozing and distribution of the snow. This will also prevent having rocks or soil suddenly appear later in the season.  

When the man-made snow is distributed and in place, it provides an excellent base for the rest of the season. It will secure enough snow through the whole skiing season even with warm weather and heavy skier wear and tear.

Snowfall

If snow is forecasted for the evening or overnight, it is best to groom in the morning. The operator then saves money avoiding double grooming. The exception is if snow needs to be pushed back to heavily used (and scraped off) areas or if the high amount of new snow needs to be mixed with old snow.  

It is important to thoroughly mix new and old snow, especially on slopes that will be used for training or competitions.  

When grooming for competitions, it is important to mix the snow and avoid layers of different consistency. The skier should not be able to ski/break through a hard top layer down to a softer layer. This creates a hole on the surface that is both dangerous and difficult to repair during the competition. By thoroughly mixing the upper 30 cm of snow, a homogeneous layer will prevent any formation of holes. This should be done regardless of any plans for water injection or salting. The consistency of the competition courses should be checked using drills and augers to make sure the firm top layer is thick enough.

Wet new snow

New wet snow may be difficult to groom since the snow will clump up in fron of the blade and easily leave uneven stripes of snow behind the tiller. It is best to minimize using the front blade or use the tiller on high speed while experimenting with the depth of the tiller (and driving with a constant speed). A slick blade and slick rear comb will also ease the work and improve the result. 

Wet corn snow

This is some of the most difficult snow to groom. It is easy to do a mistake, and usually not possible to repair or fix. Wet snow can normally only be groomed in one pass, so everything must be done correctly. The use of the blade and tiller must be appropriate while avoiding overloading the machine such that it starts digging itself down. make sure to groom before the snow freezes up in the late afternoon or evening, otherwise it may become lumpy.

Winch machines

Winch machines (also called winch cats) are now quite widespread in alpine and ski jump venues since they ease the grooming in steep and challenging terrain. The machine also makes it easier to move snow back to “wear and tear” areas, while ensuring that it does not slide uncontrollably resulting in a damaged slope.  

To be able to groom properly everywhere, the proper placements of the winch anchor points are important. This will minimize wear on the steel wire by avoiding contact points with rocks etc. It is important to realize the danger of a tensioned wire, especially since it is hard to see. The wire must therefore be secured by proper warning/strobe light and signs.

Grooming during opening hours

Grooming during skiing and opening hours should be reduced to a minimum and only be done when absolutely necessary and with clear guidelines.

When grooming during opening hours the machine must have high-beam lights and yellow warning lights on. The particular slope being groomed must be physically closed as well as signed (sign saying that grooming is going on).  

Sound signal should be used by the operator if required in the particular situation. The machine should be operated/driven in moderate speed in the most visible part of the slope.  

If the machine needs to be driven in reverse, assistant operators must to be present (and be in radio communication with the driver).  

During grooming after closing hours – especially when using a winch machine, yellow blinking warning lights and signs should be placed at the entrance to any slopes that may be used by local cabin residents or back-country skiers etc.

Grooming of off- and on lift ramps

Lift ramps are especially important for the alpine skiers. Poles and fences that may be in the way of the grooming machine must be easy to remove. List attendance staff should in addition do some manual snow-work at the ramps during the day. Off-ramps are often on top of small hills, and therefore prone to wind and blowing snow in addition to wear and tear from the skiers. Small snow fences should therefore be installed to protect and collect the snow.

Grooming for training and competitions

In addition to ensuring a homogenously firm and deep top layer of snow (see above), it is important to treat the race course correctly, especially for speed competitions (downhill and super-G). For example, sometimes new snow must be removed without destroying the base layer. This means that the venue’s operators driving the heavy machines and the event’s volunteer hill-crew must communicate and cooperate well.  

Features of a competition course/slope:

• Firm snow surface and in some cases also a layer of ice on top (not for younger competitors)
• Stable, robust and compact snow through the whole top snow layer such that no skier will punch through and create large holes. The main task is to create a hardened 10 – 20 cm thick top layer. 

Methods for creating a more robust snow surface and layer:

• Compacting the snow by using grooming machines properly
  • The machine should drive slow and with a high tiller speed. Using the tiller in reverse may produce even better results, but the last pass must be in normal tiller direction.
  • In steep terrain, winch must always be used.
  • In diagonal traverses and curves, the machine must drive in 90 degrees angles to avoid spinning or slide uncontrollably
  • Sufficient time must he planned such that the snow wil freeze and “settle” suficiently. 
• Packing the snow manually by skis or boots
  • This is appropriate if the snow is wet and there is a chance that the grooming machine will damage the surface. Foot packing is used for packing the snow before salting, and should only be done in small and steep sections.
• Using high density man-made snow
• Watering or water-injection (see main menu selection “Preservation”)
• Using sea-salt (see main menu selection “Preservation”)

Choosing the correct grooming method in different weather and snow types:

The challenges in grooming a competition course are usually related to one of the following snow conditions: 

• cold, dry snow (not dense enough)
• large amounts of new snow 
• wet, soft snow 

The table below provides an overview of recommended methods for the different conditions. All the methods require intimate knowledge of snow and weather conditions. 

Type of snow	Grooming choices
Dry and cold snow	Snow must be compacted with machine followed by 8 hours course closure. Water injection followed by grooming will ensure increased density and bonding of the snow crystals
New snow	Small amount of new snow can be compacted on the competition course if 8 hours course closure is possible. Large amounts of new snow must be removed from the course (using machines, skis, shovels, snow blowers)
Wet snow	This snow can easily be compacted. Very wet snow (more than 5% water) can be hardened with salt for a short amount of time.

For FIS competitions the final part of the grooming is often controlled by a FIS expert. The density, smoothness and “hardness” of the top layer varies with the competition format and the quality of the competitors. Different grooming is required for a FIS World Cup than for a FIS junior competition or for an IPC World Cup competition (especially for the mono/sit-ski courses).    

3

Snow parks

Building, maintaining and grooming the elements in a snow- or terrain park is described in details in the manual published in 2019 (only in Norwegian) by the Norwegian Ski Federation and the Department of Culture and Sports (see https://snowpark.no/vedlikehold/). The general advice for grooming snow parks are summarized here:  

A snow park must be groomed with a machine every day. The most important grooming task is to ensure that the slope and the shape and proportions of the elements are preserved throughout the season.  

Another important purpose with grooming is to work the snow every day such that the slope and elements do not become icy and slick due to the natural weathering and hardening. Daily grooming also ensures that the park is visually attractive. 

• In practical terms this means that snow that has moved throughout the day must be moved back to recreate the correct shape of the elements, as well as remove marks and uneven surface that is caused by wear and tear and weather conditions.  
• The following daily tasks should be prioritized:
  • move all snow back for the inrun, landing and the slope in general by using the front blade  
  • fill in and remove the divids/tracks on the take-offs by using the front blade  
  • ensure that there are no holes, waves, banking og other uneven parts on the elements or the slope due to the grooming itself. This is especially important for the take-offs, landings and where the skiers maneuver for their elements
  • ensure that the snow is well compacted without becoming too hard or icy  
  • keep an eye on and maintain/fix the elements every day. Dont procrastinate and create too many large “maintenance projects”  

Grooming, compacting and hardening the snow

The snow compacts by driving over and tilling the snow with the grooming machine. However, the compaction decreases when the driving speed increases. 

High driving speed causes more uneven compaction and more heterogenous snow quality. The risk of “wounds”, lumps or holes on or just below the snow surface increases when the skiers are putting a load of the snow. To achieve a best possible homogenous snow quality the grooming machine should hold a steady and controlled speed as well as constantly using the blade to move snow in place of break up the surface that is being groomed.

High down-pressure, deep tiller depth or high tiller speed can never compensate for poor use of the front blade. This will rather cause more wear and tear on machines, poor quality of the downhill slopes and increased fuel use. 

We should use reasonable down-pressure, depth and rotational speed on the tiller such that lumps are crushed and we archieve an even distribution of snow crystals on the snow surface, without making edges or washboard between the tiller overlaps. Gosd finishing is important, but the primary purpose is to move the snow back to its correct position.

Since most of the users of snow parks often snow-plough or skid, small divids (or “wounds”) that appear on the surface are rapidly filled in. The grooming of the downhill parts must always consider the snow type, but the best time for grooming is immediately after the park’s closing time. 

Grooming at this time ensures that the snow that has moved during the day will not freeze or settle, and the snow will be simple to handle and shape with the tiller. Grooming right after closing will also give the slope and elements longer time to harden, which is very important for the parts and elements with high wear and tear.

The wear and tear is often most prominent on areas around and on top of the “beginner ” elements. In times with wet snow that freezes over night, the take-offs are prioritized before the snow freezes.

Sections or elements that are in the shade should therefore be groomed first. It is very difficult to groom and achieve an even surface after the snow has frozen.

With falling snow the slopes should be groomed and packed for every 15–20 cm. The proportions of the elments must be preserved.  

New snow will often cause take-offs, rails and boxes to sink compared to other parts of the elements such as inrun, access trails and areas for maneuvering. This means that the rails, boxes and take-offs must be lifted accordingly to the surrounding terrain.

4

Ski Jumping

Successful grooming depends on operators with the required competency and experience. Correct and functional equipment (track setter, markings, safe rails and fences, etc) is also required to be able to present a well groomed and safe ski jump venue in all weather conditions. 

For larger venues, the packing and preparation of the snow is usually done with grooming machines and mechanical implements, while the final tuning is done manually (raking, boot packing next to fences, etc). In smaller ski jump venues, all snow packing is often done manually.

The first snow fall often consists of moist snow. This provides for a good and firm base layer. It is important to pack the base layer firm, even and smooth across the entire length and width of the hill. The section along the ski jump’s mid-line (length wise) must be preparered meticulously.

• The transition to the jump table and the jump table itself must be especially well compacted and even. This is where the ski jumper feels the highest pressure.  
• For smaller jumps with less advanced jumpers, the knoll must be well prepared and safe for the skiers.   
• In the landing hill, the preparation and packing must be especially well done towards the K-point/landing zone, the transition to the outrun and the beginning of the outrun.  

If the first snow fall consists of light and dry snow, water must be added and worked into the base layer. 

This is best done by using a snowmaking- or garden hose. Large amounts of water is not needed, since too much water may create ice and uneven sections. The water must be distributed evenly on the entire hill. After watering, manual boot-packing creates the most consistant and best base layer for the rest of the season.

When building up the ski jump with man-made snow, the process usually involves distributing and pushing piles of snow using a winch-cat. The landing hill is always built from the bottom-up. After the snow is distributed evenly, the actual tilling of the surface is done. The best winch-cat operators keep a steady and very low speed to avoid spinning and damaging the surface. It may still be required to water and boot-pack a hill at a later time.

A good and thick base layer will prevent heat from the ground to rise and transform the snow to lesser quality (for example sugar snow). Due to the requirement of the hill’s certified profile (if they are used for FIS competitions), the snow depth must be even the entire landing hill.

During the season mechanical grooming should be kept to a minimum to preserve the snow quality and snow crystals. After small and light snowfalls, the hill can be manually sidestepped with skis. However, with new snow prior to competitions grooming should take place, especially if the new show has a high moisture level.

In-run track

In the last few years, it has become common to prepare an inrun track that is cut in ice. This requires that a layer of slush is manually packed or water frozen on top of installed elements. The track is then rooted or cut in by a mechanical device.

To keep the inrun track in good and safe condition between training and competitions it must be covered by a tarp (usually stored and attached under the edge of the take-off and rolled/pulled up by the track setting device). 

Safety

Due to the high speed safety concerns, the hills must always be maintained in good order. The snow quality should be the same for young beginners as for international competitions.

It is important to check all parts of the hill for soft snow, holes or other elements that can cause the skier to crash. All guard rails and fences at the bottom (around the outrun) should be in place to prevent any injuries from “run-away” skis.

5