(This article is reproduced, with permission, from the Winter 2000-2001 (Volume 17, Number 1) issue of Tech Notes the newsletter of the Maryland Transportation Technology Transfer Center's Local Technical Assistance Program at the University of Maryland in College Park, Maryland.)

All agencies have to develop their own winter maintenance programs and policies. The Maryland State Highway Administration (MDSHA) recently summarized their strategies with a few facts and figures. In addition to plowing snow, most programs include two main strategies to handle ice:

• Anti-Icing proactive preventive winter maintenance strategy of applying a liquid chemical to roads and bridges prior to the onset of precipitation in order to prevent snow and ice from bonding to the pavement.

• Deicing -- traditional winter maintenance strategy of breaking the snow/ice/pavement bond after it has occurred. It requires more material to break the bond than to prevent it. SHA is expanding its anti-icing operations in an attempt to lessen its overall salt usage.

MATERIALS FOR THE 2000-2001 WINTER SEASON

Of a variety of possible materials, SHA uses:

• Rock Salt (sodium chloride) is the principal winter material used by SHA. It is effective down to 20 degrees Fahrenheit and at approximately $34 per ton, is relatively inexpensive.

• Salt Brine (liquid sodium chloride or liquefied salt) is a solution that can be used as an anti-icer on bridge decks prior to the onset of storms, or as a deicer on road surfaces during a storm. The material has a freeze point of -6 degrees Fahrenheit. Salt brine costs approximately 5 cents per gallon to manufacture, after the initial purchase of a brine maker for $5,500. Salt brine will be used at the brine making facilities and, in addition, will be distributed to thirteen other maintenance shops in Southern Maryland and on the Eastern Shore.

• Magnesium Chloride (mag) is the principal liquid winter material used by SHA. Mag is used in anti-icing and deicing operations just as salt brine is used. The material has a freeze point of approximately -26 degrees Fahrenheit. SHA evaluated the effectiveness and cost savings of using this material in conjunction with salt versus using salt only. At 67 cents per gallon, magnesium chloride was found to be the most effective in the colder regions of the state.

• Abrasives including sand, crushed stone, slag are used to increase traction for motorists during storms. They have no snow melting capability. SHA uses a limited amount of this material, concentrating its efforts on melting and plowing snow and ice from the pavement.

• Calcium Chloride is a solid (flake) winter material used during extremely cold winter storms.

• CMAK is a costly, non-chloride liquid chemical used in environmentally sensitive or other selected areas for winter operations.

BASIC EQUIPMENT

In addition to its fleet of salt spreading/snow plowing dump trucks, SHA uses:

• 5 salt brine machines: The shops with these machines produce brine for themselves and for surrounding shops.

• 7 truck-mounted liquid applicator spray tanks: These units are used to spray liquid chemicals on roads and bridges prior to precipitation to prevent snow and ice from bonding to the pavement (anti-icing operations).

• 177 truck-mounted saddle tanks: This equipment is used to prewet salt as the salt is spread on the highways. Prewetting salt helps it adhere to the pavement (reducing waste), go into brine solution quicker (more effective) and work at low temperatures.

• 6 fixed location overhead spray systems: These systems are used to prewet salt on trucks that do not have saddle tanks. The systems increase the effectiveness of salt.

• 1 automated bridge anti-icing system: This technology automatically sprays a liquid chemical on the I-68 bridge over Street Road in Allegany County, prior to the formation of frost or precipitation.

• 10 wing plows: A wing plow is an extra plow mounted on the right side of a plow truck, allowing crews to clear more snow from road and shoulder.