Snow removal
Snow removal is the job of removing snow after a snowfall to make travel easier and safer. This is done by both individual households and by governments and institutions.
Clearing by individuals
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In countries with light snow, brooms can be used to brush off snow from walks and other surfaces. In colder regions with more precipitation, the main tools of the private snow clearer are the snow shovel, a large lightweight shovel used to push snow and lift it, and the snow scoop, a large and deep hopper-like implement fitted with a wide handle and designed to scoop up a load of snow and slide it on any slippery surface to another location without lifting. Shovelling entails a considerable amount of work and can be a strain on the back and the heart. Each year many senior citizens and middle aged persons die from heart attacks while shovelling snow[citation needed]. Those unwilling or unable to labour, especially those with large driveways or other substantial surfaces may use a snow blower, as well as people that live in areas with long lasting winters with large amounts of snowfall. Others may hire a contractor with a plow bearing truck or a shovel. After a large snowfall businessmen with plow trucks often drive through cities offering to plow for money. A recent technological advance is the snowmelt system that heats the pavement from below and melts snow and ice after a period of time. Such systems are expensive to install and operate and they are not cost effective in areas with very low winter temperatures and large snowfalls. Some governments offer free snow clearing for the elderly and others in need.
Dealing with ice is more difficult. Snow blowers are rarely effective. Picks are sometimes used, but a solid spade can break through most ice. There is always the risk of damaging the pavement with these instruments. Icy areas can be covered with salt or some other substance, bags of which are widely available.
Clearing by contractors
Hiring a contractor with a winter service vehicle or a shovel.
In many high elevation or heavy snow accumulating areas, companies with snow removal equipment offer to provide services to remove the snow.[1] Contractors may work on a per-time basis, full season contract, or will-call status. Per-time service (or per-push) is usually invoiced monthly and customers will be charged for each time services are provided. Some companies will charge per-time and per-inch where the depth of the snow is even taken into account. A full season contract is quoted and paid upfront at the start of the season and services will be provided automatically according to the contracted terms. All companies have different terms so make sure to understand the agreement. For example, some full season contracts will expire after X amount of trips where others are unlimited. And finally, will-call service is where the client makes contact with the snow removal company to initiate a single clearing. This is not an automatic service and charges are usually higher for will-call jobs.
Snow removal services may include driveway[2] and parking area snow removal, walkway and deck handwork, and occasionally roof clearing. Contractors use hand shovels, walk behind snowblowers (or snow throwers), truck plows, skid-steers, light-weight tractors, and heavy front-end loaders. Many times, these machines will require use of tire chains to perform their tasks. Snow may be pushed by plowing methods or blown to an area of the property by snowblowers. Contracts may apply sand or salt in some locations to help melt ice accumulations.
Many snow removal contractors will require installation of snow poles or snow staking along the driveway. This is to keep equipment out of the landscaping and to help identify the perimeter of an area.
Contractors should be licensed and insured.
Clearing by cities
Cities clear snow on a much larger scale than individuals. Most cities in areas that get regular snow maintain a fleet of snow clearing vehicles. The first to be dispatched are gritters who do some plowing but also salt the road. The salt, via freezing point depression, helps melt the snow and ice and also gives vehicles more traction. Later, generally once the snow has ceased falling, front end loaders with snowplow attachments and graders cover every street pushing snow to the side of the road. Salt trucks often then return to deal with any remaining ice and snow. The trucks generally travel much faster than the plows, averaging between 30 and 40 kilometers per hour. Most cities thus have a least twice as many plows as trucks. Smaller narrow body plows, with Caterpillar tracks or huge snow tires salt and clear sidewalks in some cities, but in many others with less snow fall and/or less pedestrian traffic individuals are tasked with clearing the sidewalk in front of their homes. Ecological movements often oppose this use of salt because of the damage it does when it eventually washes off the roads and spreads to the environment in general.
In cities where snow steadily accumulates over the winter it is also necessary to remove the piles of snow that build up on the side of the roads known as windrows or snowbanks. There are a number of methods of doing this. Pulling snow is done when temperatures rise high enough for traffic to melt snow. The windrows are then broken up and spread over the road. Casting is the moving of snow by means of a shovel or plow to nearby public lands. On boulevards or highways winging back is done, which consists of pushing the snow banks further from the road. The most expensive option, but necessary when there are no nearby places to dump the snow, is to haul it away. This is most often done by large self propelled snowblowers that gather the piles of snow at the side of the road and load it into dump trucks. The snow is then dumped on the outskirts of town, or in a nearby lake, river or harbor. (Some jurisdictions have banned dumping snow into local bodies of water for environmental reasons - modern roads can be contaminated with melting salt, motor oil, and other substances.) Snow melting machines may be cheaper than moving snow, depending on the cost of fuel and the ambient temperature.[3]
The windrows created by the plows in residential areas often block driveways and imprison parked cars. The snow pushed there by any plow is a dense, packed version of "normal" fallen snow. When the temperatures are significantly below freezing this packed snow takes some of the characteristics of solid ice. Its removal is nearly impossible without mechanical means.
The largest roads and highways are the first to be cleared; roads with steep hills or other dangers are also often a priority. Streets used by buses and other mass transit are also often given higher priorities. It often takes many hours, or even days, to cover every street in a city. In some places, a snow emergency will be declared, where automobile owners are instructed to remove their vehicles from the street (or one side of a street). If cars are in the way when the plows come around, they may be hauled away by tow trucks. Some communities have standing snow emergency rules in winter, where vehicles are not allowed to be parked on streets overnight, no matter if it snows or not. After smaller snow storms only main roads are cleared while residential ones are left to be melted by the passing traffic. Decisions on immediate removal versus "natural melting" can be hard to make because the inconvenience to citizens and the economy in general must be weighed against the immediate effect on the snow removal budget at that particular moment in the season.
In large cities with heavy snowfalls like Montreal and Ottawa, the snow clearing expense for each season is an important part of the seasonal public works budget and each snow storm provokes a major logistical operation involving thousands of employees working in shifts 24 hours a day. The effort can vary greatly depending on the amount of snow. Montreal gets about 225cm of snow each winter and spends more than $128 million Canadian each year to remove it. Toronto, with about 50 per cent more population and 28 per cent more road surface, gets only 125 cm of snow a year and spends about half that.[4] The higher cost in Montreal is due to the need to perform "snow removal" as opposed to simple "snow clearing" necessitated by both the high snowfall amounts and fewer melting days.
It is estimated that Canada spends $1 billion on snow removal.[5] The employees who do this work are generally the same workers who do road maintenance work during the summer months, but in some US cities garbage trucks are also equipped with plows and used for snow removal. Many smaller US communities sign contracts with insurance companies, under which the insurance company assumes the risk of a heavy winter. The insurance company of course sets the rates such that averaged over time they will make a profit; the town is willing to overpay for snow removal in mild winters so as to avoid the risk of running dramatically over budget in the occasional severe winter.
Large organizations such as universities and airports also often have their own mechanized snow clearing force. Public transit systems generally clear bus stops while post offices clear around mail boxes. Railroads have their own snow clearing devices such as rotary snowplows.
Surface treatments
Various salts and other substances are used on roads and walkways to induce freezing-point depression, which (except in extremely cold weather) causes ice and snow to melt, greatly improving traction. These include:
- Sodium chloride (common table salt, NaCl)
- Calcium chloride (CaCl2)
- Potassium chloride (KCl)
- Magnesium chloride (MgCl2)
- Ammonium nitrate (NH4NO3)
- Ammonium sulfate [(NH4)2SO4]
- Potassium acetate (CH3COOK)
- Urea [(NH2)2CO]
- Propylene glycol (C3H8O2)
- Calcium magnesium acetate (C4H6O2Ca and C4H6O2Mg)
- Sodium ferrocyanide (hydrous, Na4Fe(CN)6•10H2O)
- Methyl alpha-D-glucopyranoside (C7H14O6) [6][7]
Sand is also sometimes used to improve traction, though after the snow and ice has melted, sandy pavement has lower traction than sand-free pavement.
The choice of treatment may include consideration of the effect on vegetation, pets, the local watershed, and effectiveness with regard to speed and temperature. Some chemicals can degrade concrete, metals, and other materials. The resulting meltwater and slush can cause frost heaving if it re-freezes, which can also damage pavement.
Snow removal tools
See also
References
- ^ "Hiring a Snow Removal Contractor". Tahoe Workz LLC Snow Removal Services. Retrieved 2008-12-21.
- ^ "Professional Snow Removal Photos". Tahoe Workz LLC Snow Removal Services. Retrieved 2008-12-21.
- ^ [1]
- ^ [2]
- ^ [3]
- ^ http://www.wrightwoodcalif.com/forum/index.php?topic=2245.0;all
- ^ http://www.chemexper.com/chemicals/supplier/cas/97-30-3.html
External links
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