Winter Plowing and Deicing: Saving Money, Salt and Labor by Distinguishing Best Practices From Urban Legends Stephen J. Druschel, PhD, PE, F. ASCE
Winter Roadway Maintenance
Winter Roadway Maintenance
Story of Three Operations: Plow, Deice & Protect the Waters Goals Safety Improve efficiency Cut costs Make the job easier Make the job better Choices Labor Materials Equipment Predictability Level of Service Level of Safety Can t Control Precipitation Temperature Drivers
Every plow driver is a scientist: Observe Hypothesize Test Evaluate But how to do evaluations when: The weather changes; The sun moves; Traffic comes and goes; And every geography has its own snow and ice?
Side by Side Comparisons Start with a really big piece of pavement Add snow or ice Plow and salt -- side by side lanes Test factors < Same time < Same weather < Same snow < Same traffic Back it up with repeatability, in both field and lab < Luck should not be your best approach
How to Improve Efficiencies Through Research? Listen to operators, supervisors and managers < Hear really hear the observations of the experts Listen to vendors what is available? Add in science and math to construct experiments < Isolate factors and test < Compare conditions < Organize, verify, emphasize Write and explain < Context and history < Emphasize characteristics and controlling factors
MSU Mankato & MnDOT: Winter Area Road Maintenance Research (WARMR) Phase I: Ice Melt Capacity Lab Study 25 products/over 50 blends +30 to -30 F Cost model Phase II: Field Study Winter 2013-14 (brrrr!) 9 lanes at 1000 ft plowing and deicing effectiveness Bridge pavement runoff and chloride timing Phase III: Field Study Winters 2015-16 and 2016-17 (grrrr!) Compare plow types and cutting edges Define controlling factors of deicing, esp. traffic effects
Experimental Units 1. Ice coupons (+30 to -30 F) 2. Pavement patches (28, 20 and 12 F) 3. Bridge cast (1000 ft x 3 lanes each way) 4. Bridge drainage (8 scuppers at 200 ft x 2 lanes each) 5. Test patches (square foot) 6. Test units (20 at 50 feet by lane width) 7. Test lanes (9 at 1000 ft and 35 mph)
Winter Area Road Maintenance Research (WARMR) 1. Evaluate ice melt capacities/effectiveness (MSU Mankato laboratory) 2. Test plows and cutting edges for differences in performance (ValleyFair!) 3. Compare deicers and prewets (Canterbury) 4. Evaluate traffic influence on deicing (ValleyFair! and Canterbury) 5. Assess effects of coloration and chloride content in prewets (Canterbury) 6. Evaluate residence time of deicer on pavement through drainage monitoring (US169 North Star Bridge) 7. Evaluate deicer movement through plow cast (US169 North Star Bridge) 8. Evaluate speed of deicers and prewets (MSU Mankato laboratory) 9. Compare effects of pavement types and ages (MSU Mankato laboratory)
Comparing Plows for Cast & Cloud
25 mph, 30 mph, 35 mph
Carver County Nine Plows
Comparing Plows for Cut & Compaction
Comparing Effects of Traffic on Deiced Lanes
600#/LM: 28 F, mid-day full sun; January 5 th Just After Plowing No Traffic Truck: Three Passes
600#/LM: 28 F, mid-day full sun; January 5 th 10 Minutes After Traffic or Plowing No Traffic Truck: Three Passes
600#/LM: 28 F, mid-day full sun; January 5 th 20 Minutes After Traffic or Plowing No Traffic Truck: Three Passes
600#/LM: 28 F, mid-day full sun; January 5 th 30 Minutes After Traffic or Plowing No Traffic Truck: Three Passes
600#/LM: 28 F, mid-day full sun; January 5 th 60 Minutes After Traffic or Plowing No Traffic Truck: Three Passes
600#/LM: 28 F, mid-day full sun; January 5 th Just After Traffic Car: Five Passes Truck: Three Passes
600#/LM: 28 F, mid-day full sun; January 5 th 10 Minutes After Traffic Car: Five Passes Truck: Three Passes
600#/LM: 28 F, mid-day full sun; January 5 th 20 Minutes After Traffic Car: Five Passes Truck: Three Passes
600#/LM: 28 F, mid-day full sun; January 5 th 30 Minutes After Traffic Car: Five Passes Truck: Three Passes
600#/LM: 28 F, mid-day full sun; January 5 th 60 Minutes After Traffic Car: Five Passes Truck: Three Passes
600#/LM: Truck Three Passes Just After Traffic 22 F, mid-day full sun 2/5/16 28 F, mid-day full sun 1/5/16
600#/LM: Truck Three Passes 10 Minutes After Traffic 22 F, mid-day full sun 2/5/16 28 F, mid-day full sun 1/5/16
600#/LM: Truck Three Passes 20 Minutes After Traffic 22 F, mid-day full sun 2/5/16 28 F, mid-day full sun 1/5/16
600#/LM: Truck Three Passes 30 Minutes After Traffic 22 F, mid-day full sun 2/5/16 28 F, mid-day full sun 1/5/16
600#/LM: Truck Three Passes 60 Minutes After Traffic 22 F, mid-day full sun 2/5/16 28 F, mid-day full sun 1/5/16
Comparing Effects of Color and Chloride Content
January 14; 28 F Cloudy; 20 minutes Rock Salt (top) vs Sand; No Prewet, Brine & Apex
Bridge Drainage Evaluation of Deicer Lost to Melting
Bridge Cast Evaluation of Deicer Lost to Plowing
Anti Icer Persistence: Pavement Patches (28, 20 and 12 F)
What Have We Learned?
What Everyone Knows, But Forgets/Ignores Drivers should slow down best improvement in safety Level of Service how clean are the roads, and how soon? Significant influence on cost, labor, materials Risk equation and management decisions Plowing/mechanical removal is generally best Environmentally friendly Quickest Clears greatest amount of snow and ice Deicing takes time; can t rush physical chemistry 20 minutes minimum (unless traffic there to help)
Proving the Hunches Rock salt works best at warmer temperatures < Not great below 20 F < Not at all below 12 F Sand is lost quickly with traffic < Creates false confidence for drivers < Chokes stormwater systems Organics in liquid deicers can cause problems < Oxygen sag in receiving streams when melt out < Stickiness can encourages corrosion Prewets of any kind don t increase melt capacity much
New Concepts and Interpretations Traffic on deicers improve performance < As little as three passes < Trucks best, but cars not bad < Tire pressure seems to enhance melt initiation and speed, plus destroys ice crystal structure Prewets don t make much difference < Unless dry snow then prewets make huge difference Sun on deicer solid has little effect < Sun on pavement improves temperature about 10 F Deicers detach from pavements quickly in drainage Plow cast removes large amounts of deicer in longer storms
Reports MnDOT Research Services Phase I: 2012-20 Phase II: 2014-43 Phase III: 2017-45
On Being Photogenic
Acknowledgements MnDOT Research Services Canterbury Park, Shakopee MN ValleyFair!, Shakopee MN MnDOT Metro District Chaska (MN) Truck Station MnDOT District 7 Mankato MN Carver County Public Works