maine road salt risk assessment project university of maine maine department of transportation
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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
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
Maine Road Salt Risk Assessment Project University of Maine September 2009
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 Road Salt Risk Assessment Project University of Maine September 2009
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
Maine Road Salt Risk Assessment Project University of Maine September 2009
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
Maine Road Salt Risk Assessment Project University of Maine September 2009
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
Maine Road Salt Risk Assessment Project University of Maine September 2009
Current Practices
Maine Road Salt Risk Assessment Project University of Maine September 2009
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
Maine Road Salt Risk Assessment Project University of Maine September 2009
*
**
*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
Maine Road Salt Risk Assessment Project University of Maine September 2009
Source: survey data
Municipal Total Winter Maintenance Expenditures per Mile 2008-09
Source:l survey data
Municipal Practices:Winter Maintenance Budgets
Maine Road Salt Risk Assessment Project University of Maine September 2009
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
Tota
l Mat
eri
al C
ost
$2
00
9 M
illio
n
Tota
l Cu
bic
Yar
ds
(10
00
) o
f Sa
lt a
nd
San
d a
nd
Gal
lon
s (1
00
0) o
f C
alci
um
Clo
rid
ed
Co
mb
ine
d
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
Maine Road Salt Risk Assessment Project University of Maine September 2009
• 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
Maine Road Salt Risk Assessment Project University of Maine September 2009
OUTLINE• Water Cycle
• Fate of Road Salt • Environmental Receptors• Pathways
•Mass Balances
• Summary of Research• Water Quality• Ecosystems
• Trends
• Summary and Conclusions
Maine Road Salt Risk Assessment Project University of Maine September 2009
Road Salt - Environmental Receptors
Maine Road Salt Risk Assessment Project University of Maine September 2009
Road Salt – Pathways toEnvironmental Receptors
Maine Road Salt Risk Assessment Project University of Maine September 2009
Road Salt – Mass Balances
Maine Road Salt Risk Assessment Project University of Maine September 2009
Ion Exchange
Maine Road Salt Risk Assessment Project University of Maine September 2009
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
Maine 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
Maine Road Salt Risk Assessment Project University of Maine September 2009
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
Maine Road Salt Risk Assessment Project University of Maine September 2009
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)
Maine Road Salt Risk Assessment Project University of Maine September 2009
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)
Maine Road Salt Risk Assessment Project University of Maine September 2009
Trucking Industry: “rust jacking”Automobiles: brake lines & electrical connectors
Vehicle Corrosion
Photo courtesy of Jeremy Williams
Maine Road Salt Risk Assessment Project University of Maine September 2009
Vehicle Corrosion
Issues:
Multiple types of corrosion
Variety of metals and alloys in vehicles
Environmental factors
Chemical factors
Field tests vs. laboratory tests
Maine Road Salt Risk Assessment Project University of Maine September 2009
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?
Maine Road Salt Risk Assessment Project University of Maine September 2009
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)
Maine Road Salt Risk Assessment Project University of Maine September 2009
Road Salt Safety
Maine Road Salt Risk Assessment Project University of Maine September 2009
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.
Maine Road Salt Risk Assessment Project University of Maine September 2009
Crashes by Road Surface Condition1989-2008
Maine Road Salt Risk Assessment Project University of Maine September 2009
County Crash Rates1989-2008
Maine Road Salt Risk Assessment Project University of Maine September 2009
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
Maine Road Salt Risk Assessment Project University of Maine September 2009
Fatality Rates Compared
Winter conditions
Dry Pavement
Maine Road Salt Risk Assessment Project University of Maine September 2009
Maine & US Crash Rates1989-2008
Maine Road Salt Risk Assessment Project University of Maine September 2009
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.
Maine Road Salt Risk Assessment Project University of Maine September 2009
Thank you
University of MaineRoad Salt Risk Assessment Team
http://mcspolicycenter.umaine.edu/?q=RoadSalt
Maine Department of Transportation