Snow and Ice Control: Guidelines for Materials and Methods (2004) / Chapter Skim
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Attachment 1 - Using Road and Weather Information to Make Chemical Ice Control Treatment Decisions
Attachment 1 - Using Road and Weather Information to Make Chemical Ice Control Treatment Decisions
Pages 27-35
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From page 27... ...
Attachment 1 Using Road and Weather Information to Make Chemical Ice Control Treatment Decisions
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From page 28... ...
The adjusted dilution potential level accounts for precipitation type and rate, snow and ice conditions on the road, and treatment cycle time and traffic volume conditions. The recommended snow and ice control material application rates depend on atmospheric and pavement conditions at the time of treatment and on how these conditions are expected to change over the time period (window)
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From page 29... ...
An adjustment level of 2 would change a low level to a high level. The end result of adding various factor adjustment levels to the precipitation dilution potential is termed "adjusted dilution potential." The final adjusted dilution potential level cannot exceed "high." STEP 6 The sixth and final step in the procedure is to make a judgment of whether an ice/pavement bond condition exists.
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From page 30... ...
Wet Low Frost or black ice (thin ice) Low Slush or loose snow Medium None Packed snow or thick ice High TABLE A-2 Precipitation dilution potential in the absence of precipitation for various wheel path area conditions Precipitation Wheel path condition Increase precipitation dilution potential by number of levels Bare 0 Frost or thin ice 0 Yes Slush, loose snow, packed snow, or thick ice 1 TABLE A-3 Adjustment table to precipitation dilution potential for the presence of various wheel path area conditions Cycle time, hours Increase precipitation dilution potential by number of levels: 0 – 1.5 0 1.6 – 3.0 1 More than 3.0 2 For traffic speeds > 35 mph Traffic volume (vehicles per hour)
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From page 31... ...
The liquid application rate data in Table A-5 for unbonded ice-pavement conditions were derived from field test data and include the influence of such variables as precipitation type and rate, pavement wheel path conditions, maintenance treatment cycle time, and traffic volume. As such, the equivalent application rates for the five ice control chemicals in Table A-6 should be considered as starting points in determining the appropriate rates for snow and ice control operations.
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From page 32... ...
7. Application rates for chemicals other than sodium chloride will need to be adjusted using the equivalent application rates shown in Table A-6.
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From page 33... ...
The application rates corresponding to a dry solid NaCl rate other than 100 lb/LM are determined by multiplying the equivalent chemical application rates for a given temperature by the ratio of the desired dry solid NaCl rate to 100 lb/LM. For example, if a 200 lb/LM of dry solid NaCl application rate were recommended at a temperature of 20°F, then switching to a 90 to 92 percent concentration of solid CaCl2 would require a slightly higher application rate of 216 lb/LM.
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From page 34... ...
Traffic Volume (vph) Slush, Loose Snow, or Packed Snow in Wheelpath (Yes or No)
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From page 35... ...
R e c o m m e n d e d T r e a t m e n t Figure A-2. Form 2 -- Example snow and ice control treatment design worksheet.
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