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Attachment 2 Example of Designing a Chemical Snow and Ice Control Treatment

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B-2 ATTACHMENT 2 EXAMPLE OF DESIGNING A CHEMICAL SNOW AND ICE CONTROL TREATMENT This Attachment provides an example of how to select a snow and ice control treatment using the treatment design procedure given in Attachment 1--Using Road and Weather Information to Make Chemical Ice Control Treatment Decisions. Assume a snow and ice winter weather event is in progress on January 16, 2002. It is 1100 hours and a treatment is being designed for immediate implementation. The available weather and pavement condition data are arrayed on Form 1 (Figure B-1). Using the data in the column for 1100 hours on Form 1 and the data in Table A-1, go to Form 2 (Figure B-2) and complete the column for 1100 hours. Precipitation and Trend: The precipitation is ordinary snow falling at a moderate rate. The trend is toward lighter intensity; however, we will choose the conservative approach and call it ordinary snow falling at a moderate rate. From line 1 of the Precipitation Dilution Potential Table A-1, the dilution potential is "medium." This is entered on Form 2. Cycle Time: From Form 1, the anticipated cycle time is 2 hours. From Table A-4, the cycle time adjustment is "1." This is entered on Form 2. Wheelpath Condition: On Form 1, there is no slush, loose snow, or packed snow in the wheelpath. From Table A-3, the adjustment for this is "0." This value is entered on Form 2. Traffic Volume: From Form 1, the maximum traffic volume is likely to be 100 vph and the maximum speeds will be in the range of 50 mph. From Table A-4, the traffic adjustment is "0." This value is entered on Form 2. Adjusted Dilution Potential: There is only one required adjustment of +1 level to the precipitation dilution potential of "medium." This comes from the cycle time effect and makes the adjusted dilution potential to "high." Note that even though the sum of the adjustment may exceed "high," the adjusted dilution potential cannot exceed "high." Pavement Temperature and Trend: From Form 1, the projected pavement temperature for 1 to 2 hours after treatment is 28F; this is entered for pavement temperature and trend on Form 2. Ice/Pavement Bond: From Form 1, the ice/pavement bond has been determined from field reports to be "no." This is entered on Form 2. Treatment: Using the data on Form 2 for Adjusted Dilution Potential, Pavement Temperature and Trend, and Ice Pavement Bond, go to Table A-5 and determine the proper application rate for solid sodium chloride. In this case, the appropriate application rate is 190 lb/LM of solid NaCl.

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B-3 Weather and Pavement Condition Sheet Date 2002 1/16 1/16 1/16 1/16 1/16 1/16 1/16 Time 1100 1200 1300 1400 1500 1600 1700 Forecast (F) or Actual (A) A F F F F F F 1 1 1 2 Precipitation Type OS OS OS PS None None None Precipitation Intensity M L L L (H, M, or L) Percent Clouds 100 100 100 100 90 70 50 Weather Data Cloud Density (H, M, or L) H H M M L L L Radiational Effects 0 0 0 0 + 0 (0, + or ) Air Temperature (F) 25 25 25 24 23 22 21 Air Temperature Trend 0 0 (0, + or ) Wind Velocity (mph) 6 7 8 8 9 10 12 Wind Direction SE S SSW SSW W W NW Relative Humidity (%) Dewpoint (F) Pavement Temperature 28 28 27 27 26 26 25 (F) Pavement Condition Data Pavement Temperature 0 0 0 Trend (0, + or ) Treatment Cycle Time (hr) 2.0 Traffic Speed (mph) 50 Traffic Volume (vph) 100 Slush, Loose Snow, or Packed Snow in No Wheelpath (Yes or No) Ice Pavement Bond No (Yes or No) Text Forecast and Other Operational Data 1 Ordinar y snow. 2 Powder snow. Figure B-1. Completed Form 1--Example weather and pavement condition worksheet.

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Agency________________________ Date__________________ Route__________________________________ Operator_________________________________ Date 1/16/02 Time 1100 Dilution Potential Precipitation and Trend (L, M, or H) M Cycle Time (0, +1, or +2) 1 Wheel Path Condition (0 or +1) 0 Traffic (0 or +1) 0 Adjusted (do not exceed H) H Pavement Temperature (F) and Trend 28 Ice/Pavement Bond (Yes or No) No Recommended Treatment 190 lb/LM of solid sodium chloride Figure B-2. Completed Form 2--Example snow and ice control treatment design worksheet.