The Salt Institute receives many questions, from the public and, especially, from winter maintenance agencies, about effective winter maintenance.   For agency personnel interested in the latest and best information, you may want to consider joining the snow-ice listserv initiated by the Transportation Research Board.   Below are some of the common questions received at the Salt Institute:

QUESTION: Why is a written policy on snow and ice control practices so important?

ANSWER: A written policy or even the existence of a generally-known verbal policy may avoid litigation or reduce payout in the event of litigation resulting from a vehicular accident or slip-and-fall case. If you can show that you have a policy reflecting "generally accepted practices" and you have done what is considered "reasonable and prudent" you have a fighting chance in court. You should have written documents on everything you do related to snow and ice control: when operations began, what was done and all details throughout the event. You should have everything documented because a court case will be some years in the future when the memory of the event may fade or persons involved may no longer be employed. Accurate records may negate a potential lawsuit or mitigate the process and/or potential payment. Written policies are great public relations tools, often used to advise the public what and when operations will be done.

QUESTION: The Salt Institute seems to indicate pavement design could alleviate some problems with snow and ice control, could you be more specific.?

ANSWER: If all departments collaborated during the design phase of a new street or highway many problems could be eliminated. One almost constant complaint is water running back across the pavement and re-freezing when snow left on the high side of a curve melts. Building a break-point so that melting snow or ice would drain/run off rather than onto the pavement would solve many problems. All water regardless of source should be directed away from the pavement at all times.

If all water could exit the pavement and not be repeatedly splashed by traffic back onto sidewalk, pavement or wherever, the re-freeze on the pavement would not be a problem requiring further treatment long after the event. This would be especially true with the need for windshield washer fluid sometimes long after the storm event.

QUESTION: How does the Salt Institute determine its recommended application rates?

ANSWER: We surveyed many agencies years ago and have adjusted our recommendations as new equipment and experience have dictated. The application rates are meant as guidelines. All guidelines should be subject to revision based on the storm conditions present at the time. These rates also were based on ambient temperatures because that was the only information generally available at that time. There is far more information available now and in the near future temperatures will be based on pavement temperatures. Some agencies now think those early thoughts were "low." Possibly because there was an effort to keep figures low in the early days of the environmental movement.

These application rates may be revised as we have more experience with many new aspects of snow and ice control, especially new computer and weather technology systems.

QUESTION: I’ve heard there are some new on-board pavement temperature sensing devices available. What information can you provide?

ANSWER: Just a few years ago, most agencies had to rely on ambient/air temperature because that was all that was available. Today there are many systems that will provide pavement temperature which is what is needed to more accurately determine what activity is required to combat ice and snow. In-pavement sensors have been provided with most road weather information systems for many years and there are now vehicle-mounted devices that read the pavement temperature as you drive the road.

The units are mounted under the vehicle, mirror-mounted or at some location so as to be somewhat protected. The SHRP anti-icing program has tested some new devices and reports from the field say they work great. Kentucky DOT says they provide instantaneous temperature even when switching from at-grade to bridge decks. The Village of Hanover Park, Illinois has an on-board sensor and says it works very well, providing necessary information as to whether further treatment should be necessary. The cost varies from a few hundred to a few thousand dollars.

Two devices available are from:

Sprague Controls, Inc.                           Control Products, Inc.
1140 N.W. 3rd Avenue                          1316 N.E. 134th Street
Canby OR 97013                                       Vancouver WA 98685
800/441-2048                                          360/571-0988

QUESTION: We’re just getting ready to begin spreader calibration and would appreciate any information available. Do you have any advice?

ANSWER: First and foremost, please make sure the spinner is turned off, out of the way or otherwise disengaged! Don’t place hands or other body parts near the spinner during calibration. I’m amazed at the number of agencies that have not gotten in gear with the calibration process. I’m very pleased that you are taking the initiative and can assure you your effort will be worthwhile. You should know what amount of material you are using for the varying storm conditions, for your own benefit and that of the questioning public. Employee safety cannot be overstressed! The calibration process is very simple, it just takes a little time. Calibration cards are available on this website.

QUESTION: Is prewetting something affordable enough and effective enough for smaller agencies to consider using it?

ANSWER: Prewetting is one more tool to be used to eliminate snow and ice from a street or road as quickly as possible, sometimes when temperatures are too low for straight salt to be as effective. Several prewetting agents are available: liquid sodium chloride, liquid calcium chloride, liquid magnesium chloride, liquid CMA, liquid potassium acetate and even straight water.

The cost varies with each prewetting agent and with the type of equipment used. On-board equipment is the most expensive and the most effective. Home-built equipment is probably the least expensive and most serviceable. The cost may range from a few hundred to a few thousand dollars depending on the system and product used. The bottom line is prewetting will make the salt work faster and at lower temperatures. If you want to eliminate the hazard presented by snow and ice, prewetting will help do it faster.

Liquid sodium chloride may be produced in-house for about 6 to 10 cents per gallon, calcium and magnesium chloride may be purchased for about 50 cents per gallon. Liquid sodium chloride must be stored in a heated facility because it will freeze at some temperatures in snow belts around the world.

QUESTION: What are your thoughts regarding road weather information systems (RWIS) and weather radar systems?

ANSWER: Several types of weather systems are on the market. They provide different information and all is useful. The more information you have the better prepared for the storm event and the better to deal with it as it unfolds. One little bit of information that might go a long way toward paying for any system would be the fairly accurate knowledge of when the event will begin and cease, possibly eliminating the need for premature or for further end-of-storm treatment. Several systems are in use and most agencies like the accuracy of information provided.

These systems don’t just provide winter weather information but also provide information helpful for construction, paving, planting and other operations.

QUESTION: What are other cities doing with anti-icing and how much is it costing them?

ANSWER: I think you were asking what is being done with the "new" anti-icing techniques using liquids. Fifteen state DOT’s tried and tested anti-icing and they liked it. Several cities have also tried anti-icing and/or the use of liquids for winter maintenance and they seem to like it. Some agencies are using liquids in order to eliminate abrasive use which may be causing a PM 10 problem. Costs are sometimes difficult to establish because of differing accounting methods.

QUESTION: What is a reasonable "cycle time", how many plows and spreaders should be used to achieve this cycle time? What equipment is required?

ANSWER: These are questions that can only be answered by the individual agency. What one municipality or highway department thinks satisfactory may not be satisfactory for another. Ultimately, the public demand or perception of service, level of service, will determine what an agency should be doing. Plowing and spreading cycle time may vary from as little as 45 minutes to as much as several hours. Cycle time is very dependent on the average daily traffic (ADT). What is required on a road with 200,000 ADT is probably not required on a 200 ADT road.

QUESTION: How much liquid calcium chloride should be used for prewetting salt?

ANSWER: It depends on the type of prewetting system used. The most efficient method of prewetting is with on-board equipment applying the liquid at the spinner, but that may also be the most expensive. There is thought that between 4 to 6 gallons may be used with on-board equipment. Prewetting on loader bucket prior to placing salt in spreader and wetting spreader load requires 6 to 10 gallons per ton of salt. Injection-wetting the entire stockpile is done at 8 gallons per ton using a 42 percent solution of liquid calcium chloride heated to 90 degrees Fahrenheit. The salt must be below 35 degrees Fahrenheit for proper recrystallization to occur. Other liquids available for prewetting include magnesium chloride, sodium chloride and calcium chloride.

QUESTION: What feedback are you getting regarding anti-icing?

ANSWER: So far most agencies trying/using anti-icing (with a variety of products/equipment) seem to like it. It apparently won’t satisfy all storm conditions but does have a place in the tools for combating winter storms. One complaint was the cost of anti-icing equipment. Several agencies solved that problem by designing and building their own equipment which seems to work very well.

QUESTION: Why are we no longer permitted to dump snow from the central business district (CBD) into the river?

ANSWER: The snow collected from the CBD may be contaminated with heavy metals and other debris not permissible for disposal in the river. The level of chlorides is not the concern so much as other things that might be in the snow. Sometimes, permits are required for the deposition of snow into waterways and landfills. Don’t attempt to deposit anything anywhere unless you have authorization and know that what you are doing is legal. Some little thoughts are beginning to surface that suggest heavy metals may not be as much a problem as once thought.

QUESTION: Is there much vegetation damage immediately adjacent to or near the shoulder of road?

ANSWER: Not very much that I see, but you should always check as you ride the roads. If you should note some damage, record and report it for investigation. Is it salt damage or is there another problem? Don’t assume until you have analyzed the situation. You may note that some agencies actually scalp the soil and vegetation as much as several feet from the pavement shoulder in order to ensure space for disabled vehicles, storage for future snow and to decrease the potential for accidents.

QUESTION: Are many agencies using tandem plowing operations?

ANSWER: Yes, tandem plowing operations are employed by many agencies both small and large for a variety of reasons. Although this effort may seem expensive on first thought, it gets the job done very quickly. The objective of the removal effort is to get the snow off the roadway as quickly as possible. You have to consider what you hope to achieve and what are you willing to pay for that effort. Tandem operations may consist of two to as many as ten or more plows. In SI’s Snowfighters video there’s one scene with more than fifteen plows working in tandem.

QUESTION: What deicer is effective at minus 23 degrees Fahrenheit?

ANSWER: If you have ice or snow on the pavement at this temperature you have major problems but there are deicers that still might work. Calcium chloride and magnesium chloride are probably the first two to consider because of cost and availability. If you just consider the eutectic temperatures ( the lowest temperature a product will remain in solution), aluminum chloride, calcium chloride, lithium chloride, magnesium chloride, ethylene glycol and methanol might all work. There is some product that will probably do the job if you can afford it. The best advice is to rid the pavement of the problem during the event when temperatures are usually much higher. If you wait until the storm is over, when temperatures often drop dramatically, you may have little chance to clear the pavement until temperatures rise.

QUESTION: Are many agencies using partnering in salt storage?

ANSWER: In the last several years several agencies have tried it with great success. There seems to be a renewed effort to try it now and it’s working very well according to Bill Gray, director of public works, City of Urbana, Illinois, which is partnering with Champaign County and Urbana Township, using a storage building large enough to house a full year’s supply for each agency. "It’s working very well. We have plenty of capacity with a full year’s supply for each agency. We’ve had excellent accounting of use just by keeping records of each truck load used". Each agency needed better storage and the county had available land for the facility.

The Illinois Department of Transportation District 1, (Chicagoland) has agreements with many agencies. The initial load is from an ILDOT yard but subsequent loads may be obtained from partnering agencies to avoid deadheading and stay on top of the storm. ILDOT has even instituted direct resupply from salt producers to some of the partners in order to avoid shuttling supplies from DOT facilities to partners and double hauling.

You might want to review Roads and Bridges December 1996 issue regarding the cooperation between Wisconsin DOT and Columbia County, WI. In Wisconsin, WIDOT contracts with the counties to perform all maintenance on the state trunk highway system and the DOT often helps with the materials needed for the performance of work on the state system.

These are just a few examples of partnering for the mutual benefit of all. Salt storage is an especially timely subject. The same concept is being used with many other phases of public works and highway operations. Access your needs and check with your neighbors to see if there could be a mutual need and benefit.

QUESTION: What spreading equipment is used for anti-icing?

ANSWER: A variety have been tried and tested, some homemade and some purchased, some inexpensive and some expensive. If you endeavor to use anti-icing you should obtain a copy of the Manual of Practice for an Effective Anti-Icing Program: A Guide for Highway Winter Maintenance Personnel, FHWA-RD-95-202. This document is available through the National Technical Information Service, Springfield, VA 22161. It is the most authoritative document on anti-icing to date. Brine making equipment is also discussed.

Equipment of your own design will probably be the least expensive and most serviceable. If it’s simple you can replace or repair it, maybe even during a storm event when so much equipment seems to fail. Simple designs also usually require less inventory of spare parts.

QUESTION: What materials are being used for snow and ice control besides salt?

ANSWER: Salt (sodium chloride) continues to comprise the bulk of material used for winter maintenance. Calcium chloride, calcium magnesium acetate, magnesium chloride, potassium chloride (in both solid and liquid form) and an assortment of packaged products (mixed deicers) are being used but much lessor extent.

QUESTION: How does one plow an overpass or bridge that is above another roadway and avoid plowing snow onto the road below?

ANSWER: If there is any way to avoid plowing snow onto any other roadway below, please try to do so. Plow it off the structure rather than cast it over the side. The plowed material might contain debris, hardpack, ice chunks or other foreign matter that might damage vehicles below or injure someone. The material could startle the unsuspecting motorist and cause a crash.

Agencies use a variety of methods to avoid the problem; decreasing speed so that the material is not pushed over the edge, storing the material at the edge of the structure to be loaded and hauled later, straightening the blade to try to push the material straight ahead and off the structure and a variety of other methods.

If the material is plowed to the edge, due care must be given to avoid creating a ramp that might allow a vehicle to catapult over the side. This also is a problem with plowing snow against guardrail.

QUESTION: Are the road weather information systems really worthwhile?

ANSWER: I think they are because they provide the latest weather information available via computer technology which almost everyone has today. You can see what's happening over a wide- range of territory but more specifically to the area where most of you storms will originate. You can track real-time what a storm is doing, how fast it is moving and what you might expect once it arrives in your area.

QUESTION: Are studded tires still used?

ANSWER: Yes, studded tires are still used and are permissible in some areas for specific time periods, but their use has been reduced. Studs have been determined to create damage to highways. Also, chains are still used in some areas. The severity of winter storms in a given area often dictates the use of these traction devices.

I don't recall ever hearing the problem in North America, but there are problems with particulate matter ground by studs from the road surface in Japan.

QUESTION: What additives are used in deicing salt and are they harmful to humans?

ANSWER: The only additive currently added to deicing salt is anticaking agents, either ferric ferrocyanide (Prussian Blue) or sodium ferrocyanide (Yellow Prussiate of soda). Both additives are non-toxic and harmless to humans. The Federal Food and Drug Administration allows the use of YPS anticaking agents in food grade salt.

QUESTION: Will salt freeze?

ANSWER: Yes, if moisture is present. The combination of moisture and salt forms a hydrated compound which freezes. However, after thawing the salt returns to its original composition and there is no change in its effectiveness. To prevent freezing, stockpiles should always be covered when not being used and recovered after loading. Preferably, all salt should be under a permanent roofed structure.

QUESTION: What are the latest publications offering information on salt use and potential affects on the environment?

ANSWER: The best information we have is, Highway Deicing: Comparing Salt and Calcium Magnesium Acetate, TRB Special Report 235 and The Use of Selected Deicing Materials on Michigan Roads: Environmental and Environmental Impacts. We see them as positive thoughts that salt is still the deicer of choice. They offer many thoughts and we would be pleased to provide them as necessary.

QUESTION: Can salt be stored for long periods of time?

ANSWER: Absolutely yes! No matter what type of salt you use, it can be stored many years, if not indefinitely, if it is stored properly, protected from rain and snow. Salt does not lose effectiveness when stored and only becomes ineffective once it goes into solution and is diluted beyond it's capacity to further lower the freezing point of the solution.

Mined salt is possibly 300 million years old. Solar salt may be relatively new (possibly having been harvested in the last year or so) but may be used and stored the same as rock salt.

QUESTION: What's the latest information regarding use of ground-speed oriented spreader controls?

ANSWER: There should be little doubt that ground-speed spreader controls are worth their cost. The latest models not only allow you to spread the precise amount you want, but they provide accurate information as to what was spread. They help determine effectiveness of operations, with whatever material used, and provide some information necessary to modify action to continue to provide safe highways.

QUESTION: What are other agencies doing and what equipment are they using for winter maintenance these days?