|Crotched and SMI® Snowmaking 101
New England's Highest Production Capacity Snowmaking System!
Crotched is indeed among the ski resorts in the US that can boast the largest per acre production capacities. In terms of energy efficiency, we can lay claim to be among the best. These efficiencies are due to the fact we operate with 100% Fan gun which no one else can claim in New england. This capability is due to fan guns that operate with a water only system (read below on how you make snow). We do not have to operate with expensive and inefficient diesel generators to pump high pressure air in a network of pipes all over the mountain. Each SMI fan gun that we use have their own on-board air compressor. Along with these advantages, it is generally believed that Fan Gun snow provides a better skiing snow. A man-made snow that has a lower water content which translates into softer snow with less hard pack conditions.
At Crotched we have an extensive network of stationary fan type snow machines. What you can't see is the large underground network of electrical wire and over 3,000 feet of 12" and 8" pipe connecting over 100 tower snow guns. As stated above, this system allows us to pump a capacity of 200 gallons per minute per acre or over 6,000 gallons of water per minute on our slopes. It takes about 160,000 gallons of water to make one acres of snow one foot deep. This is 20 tons per minute or 1,250 tons per hour. Or stated another way, a truckload every minute. Pumping some 6,000 gallons of water per minute translates to about six inches of snow over the entire ski area in a 12 hour night!
When nature doesn't cooperate by providing natural snow, the Crotched Mountain snowmakers take over. Given water, electricy and temperatures below 32°F (0°C) snowmakers can provide snow.
Basically, snow is small particles of ice. So, the really old way of making snow, and the way they still do in the tropics and for special events, is to grind up blocks of ice. However, this is very expensive and labor intensive for larger scale requirements, so, if possible, machines that convert water into snow directly and on site are used.
These snowmaking machines make snow by breaking water into small particles, cooling the water by causing them to move through cold air, nucleating the water particles and distributing the resulting snow on a surface. Why don't people just sprinkle water to make snow? Water is a unique material, it expands when it freezes and it has high heat of fusion, thus your ice cubes float and last a long time. Heat of fusion means that one can cool a pound of water say from 65°F (18.3°C) to 64°F (17.8°C) or 34°F (1.1°C) to 33°F (.6°C) by removing 1 BTU. But to convert one pound of liquid water at 32°F (0°C) from a liquid to one pound of ice at 32°F (0°C) requires the removal of 144 BTUs. In summary, a large amount of heat removal (cooling) is required in snowmaking. Also, water can be cooled well below 32°F (0°C) and still stay a liquid unless it is nucleated. This phenomenon is called supercooling.
So a snowmaking machine (a) breaks the water into small particles, (b) cools the water to 32°F (0°C), (c) removes the heat of fusion, and (d) nucleates. Snowmaking requires relatively large quantities of water, for example, to cover an area of 200 feet (61 meters) by 200 feet (61 meters) with 6 inches (15 centimeters) of snow, one would need 20,000 cubic feet (566 cubic meters) of snow or 1,000 cubic feet (283 cubic meters) of water. This is 82,000 gallons (310,000 liters) of water or 11 truck tankers full. Thus, an excellent water supply is needed and the water pressure should be at least 100 PSI (pounds per square inch) (7 Bar) or 230 feet TDH (total dynamic head).
Snowmaking, while usually used at ski areas, is also used for frost protection on construction projects, freeze protection of crops, automotive and aircraft testing, and sewage disposal. There are over thirty snowmaking companies around the world. SMI® (the makers of Crotched's fan guns) is one of the largest companies dedicated primarily to snowmaking.
Surface conditions should also be considered. An inch or so of new snow coupled with freezing temperatures and good grooming will usually provide very good skiing conditions. A granular surface may range from somewhat slick conditions, before it is skied or groomed, to a loose, sugar crystal like surface that is very skiable. After an extended cold spell and build up of the ski base, the skiing can be very good even if the temperature shoots up into the forties and fifties during the day. In late winter these conditions are called "spring skiing" which means that there is plenty of snow. Daytime, above-freezing temperatures cause the surface to become granular, like rock salt and skiing can be from fair to good depending on the depth of the base and the previous night's temperature. Overnight temperatures in the low twenties will refreeze particles producing loose granular "snow". A report that contains the wording "icy spot" should NOT be regarded as a clear indication that skiing is likely to be poor. Some of the best ski days may be accompanied by icy spots where skiers have repeatedly turned and scraped their skis across a particular spot on the slope causing the surface to "ice-up".
All skiers should keep in mind that in spite of the area's very best efforts and sophisticated equipment, there may always be the unexpected, such as a fallen branch, a hidden root, or a chunk of ice on any slope.
Enjoy the Winter Season and we'll SEE YA ON THE SLOPES!