Maine Road Salt Risk Assessment Project University of Maine Maine Department of Transportation.

Maine Road Salt Risk Assessment Project

University of Maine

Maine Department of Transportation

Project Goals

•Develop among stakeholders a common understanding of the public policy issues and the relationships of funding, current research, levels of service, and risks associated with the use of road salt.

•Inform the policy making process in Maine related to winter road maintenance practices.

Maine Road Salt Risk Assessment Project University of Maine September 2009

GOOD NEWSLevel of Service = High

Public Safety = Improved (causal link unclear)

Environment = Less Sand/Silt in Runoff


GOOD NEWSLevel of Service = High

Public Safety = Improved (causal link unclear)

Environment = Less Sand/Silt in Runoff


BAD NEWSLevel of Service = High Cost

Public Safety = Corrosion (vehicle/infrastructure)

Environment = Salt Effects

UMaine Project Research Team

•Per Garder, Professor of Civil Engineering

•T. Olaf Johnson, Graduate Research Assistant, Department of Civil Engineering

•Margaret McKee, Research Associate, Margaret Chase Smith Policy Center

•Charles Morris, Senior Research Associate, Margaret Chase Smith Policy Center

•Kenneth Nichols, Professor of Public Administration

•John Peckenham, Director, Maine Water Research Institute & Senior Research Scientist, Senator George J. Mitchell Center for Environmental and Watershed Research

•Jonathan Rubin, Professor of Resource Economics & Policy, School of Economics & Margaret Chase Smith Policy Center

•Adam Stern, Graduate Research Assistant, School of EconomicsMaine Road Salt Risk Assessment Project University of Maine September 2009

Project Advisory Committee•AAA•Federal Highway Administration•Federal Motor Carrier Safety Administration•Maine Auto Dealers Association•Maine Chapter of American Public Works Association•Maine Chiefs of Police Association•Maine Custom Auto Association•Maine Department of Environmental Protection•Maine Department of Inland Fisheries and Wildlife•Maine Department of Public Safety•Maine Department of Transportation•Maine Fire Chiefs Association•Maine Motor Transport Association•Maine Municipal Association•Maine State Legislature •Maine Town and City Management Association•Maine Turnpike Authority•U.S. Department of Transportation•U.S. Geological Survey, Water Resources Discipline


Maine Roads

22,830 miles of public roads

• MaineDOT 4,164 mi. (18%)

• MTA 635 lane miles

• 488 towns/cities

• 3 reservations

• counties

Maine Winter

•20-40 storms November to late April

•Salt preferred chemical since 1930s

• Readily available

• Effective

• Relatively low-cost


Snow Removal Practices

De-icing• Plow after 1-2 inches. Spread sand and salt mix• Remove snow pack (salt)• Clean up sand at end of season

Disadvantages of Sand• Build up & drainage problems on roads• Siltation of waterways • Air quality issues• Benefit is temporary. No melting properties • Skidding hazard on pavement• High cost of storage, handling


Anti-Icing

1996 FHWA SHRP Anti-Icing Manual of Practice

• Pre-Wet Solids

• Pre-Treat Roads

MaineDOT initiated in late 1990s (salt priority)

• Mostly salt

• Requires accurate forecasting, timing

• Bare pavement sooner after storms


Current Practices


MaineDOT• Anti-icing 95% • Salt is still most effective choice above

15o

• Pre-wetting salt with brine, with Ice-B-Gone, & with blend

• Pre-treating small percentage of roads

Municipal/County• Practices vary widely

•Sand and Salt Liquids•De-Icing Anti-Icing and Pre-Treating

Materials•Salt (NaCl)

•Winter Sand (mixed with salt)

•Salt Brine (23% salt in water, for pre-wetting or pre-treating)

•Chlorides• Calcium Chloride (CaCl2)

• Magnesium Chloride (MgCl2)

Ice-B-Gone (MgCl2 blend with by-product of alcohol distillation process)

•Acetates • Potassium Acetate (KA)• Calcium Magnesium Acetate (CMA)

•Carbohydrate based solutions • Corn, Beet, Grains

Salt Usage in Maine 2008-09


*

**

*estimate based on survey data

**based on national estimate (USGS)

Municipal Practices: Percent Using These Materials

winter 2008-09 Source: survey data

Level of Service (MaineDOT)

Priority 1 (26%)6 daylight hours to bare pavement, plow cycle 1 to 1 ½ hours40-45 mphRoute length 10 centerline miles

Priority 2 (36%)8 daylight hours, plow cycle 1 ½ to 2 hours35-40 mphRoute length 12 centerline miles

Priority 3 (38%)24 hours, plow cycle 1 ½ to 2 hours35 mphRoute length 14 centerline miles

Source: MaineDOT

Level of Service: Municipal


Source: survey data

Municipal Total Winter Maintenance Expenditures per Mile 2008-09

Source:l survey data

Municipal Practices:Winter Maintenance Budgets


Personnel

Equipment

Materials

Source: survey data

Material Cost MaineDOT

Source: MaineDOT

Material Cost MTA

23

3331

27

42

33

-$0.3

$0.2

$0.7

$1.2

$1.7

$2.2

0

5

10

15

20

25

30

35

40

45

50

2001 - 02 2002 - 03 2003 - 04 2004 - 05 2005 - 06 2006 - 07 2007 - 08 2008-09

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Sand Salt Calcium Total Material Cost Number of Storms

Source: Maine Turnpike Authority

Total Winter Maintenance Expenditures 2008-2009

*estimate based on survey data

*

Factors in snow control policy


• Level of Service• Temperature • Speed of response • Availability & amount of material • Melting properties • Cost • Equipment, training • Infrastructure & environmental impact• Driver reaction to snow clearing • Vehicle condition

Road Salt Effects On Environmental Quality


OUTLINE• Water Cycle

• Fate of Road Salt • Environmental Receptors• Pathways

•Mass Balances

• Summary of Research• Water Quality• Ecosystems

• Trends

• Summary and Conclusions


Road Salt - Environmental Receptors


Road Salt – Pathways toEnvironmental Receptors


Road Salt – Mass Balances


Ion Exchange


NaCl + H2O

Na+ + Cl- aqueous

2Na+ Ca2+

Na+ K+

2Na+ Mg2+

Na+ H+

In soil

Road Salt and Water Quality•Short Term

• Increased Na and Cl in surface waters

•Long Term• Increased Na and Cl in ground waters• Increased salinity of ponds• Soil chemistry change through ion exchange

-release of Ca and Mg then H (acidification)• Soil “stores” salt and releases it over time

• Trends• Increased Na and Cl in surface waters (0.2 to 2

mg/L/yr)• Increases persist for months to decades• Occurrence of high salt waters limited to near

roads and storage areasMaine Road Salt Risk Assessment Project University of Maine September 2009

Road Salt and Ecosystem Quality

•Short Term• Increased attraction of salt-loving species• Foliar burning• Loss of salt sensitive species (plant and animal)

• Long Term• Decrease in surface water diversity• Dominance by salt-tolerant invasive species (e.g.

phragmites)• Vernal pool decline• Toxic thresholds exceeded for sensitive species

• Trends• Loss of overall diversity• Increases in invasive species (plants)• Ecological footprint ~ 600 meters wideMaine Road Salt Risk Assessment Project University of Maine September 2009

SUMMARY AND CONCLUSIONS

•Road Salt Affects Water Quality and Ecosystems

(600 m)

• Seasonal Effects- Larger Magnitude, Shorter Duration

• Chronic Effects- Lower Magnitude, Longer Duration

•Reversibility

• Seasonal Effects are mostly reversible

• Chronic Effects- Require years to decades to change


SUMMARY AND CONCLUSIONS

•Trends

• Increase in Chloride in surface waters and ground water

• Cation exchange leads to nutrient depletion and acidification of soil and water

• Loss of biodiversity

• Increased prevalence of invasive species


Infrastructure Corrosion

Bridgeso 2,279 bridges in Maine

o 649 “structurally deficient or functionally obsolete” 28% (2007)

o 386 MaineDOT Watch List (2008)

Pathways of corrosion

• Corrosion of steel

• React with cement paste

• Physical impact on cement (atmospheric)


Infrastructure Corrosion

•Increase # of freeze/thaw cycles.

•All chlorides equally high in corrosion of rebar.

•MgCl2 and acetates highest impact on paste deterioration.

•All chlorides high impact on atmospheric corrosion, with CaCl2 and MgCl2 higher due to retention of moisture. NCHRP Study 577 (2008)


Trucking Industry: “rust jacking”Automobiles: brake lines & electrical connectors

Vehicle Corrosion

Photo courtesy of Jeremy Williams


Vehicle Corrosion

Issues:

Multiple types of corrosion

Variety of metals and alloys in vehicles

Environmental factors

Chemical factors

Field tests vs. laboratory tests


Hexavalent Chromium

End-of-Life Vehicle Directive, July 2007 deadline

Eliminated:

• 1990s Volvo, Opel

• 2003-2006 GM

• 2004-06 VW

• 2005 Ford

• 2006 Toyota, Hyundai

• 2007 Nissan, DaimlerChrysler

Alternatives?


Conclusions

Chloride-based salts are all corrosive to motor vehicle components in laboratory tests.

Magnesium and calcium chlorides retain moisture longer.

Inconsistency of laboratory results means no risk ranking of chemicals possible. (Fay, 2009)

Diffusion of chloride into porous materials is linked to moisture.

Field conditions may contribute more to relative corrosiveness than chemical or coating. (NCHRP, 2008)


Road Salt Safety


Data

All police reported accidents in Maine from 1989-2008.

Annual estimated vehicle miles traveled (VMT) for all individual counties in Maine as well as state totals.


Crashes by Road Surface Condition1989-2008


County Crash Rates1989-2008


Total Crashes

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

January

Febru

aryMarc

hApril

MayJune

July

August

September

October

November

December

2000

2002

2004

2006

2008


Fatality Rates Compared

Winter conditions

Dry Pavement


Maine & US Crash Rates1989-2008


Costs of Accidents

• Maine accident data shows a 10 year average cost of $1.5 billion dollars annually

• Cost per accident measured in constant $2008

• The total number of accidents has fallen 26% over the decade.

• Possible reasons: driver behavior, vehicle technology, road way improvements, winter maintenance.


Thank you

University of MaineRoad Salt Risk Assessment Team

http://mcspolicycenter.umaine.edu/?q=RoadSalt

Maine Department of Transportation

Maine Road Salt Risk Assessment Project University of Maine Maine Department of Transportation.

Documents

Transcript of Maine Road Salt Risk Assessment Project University of Maine Maine Department of Transportation.