Highway Deicing: Comparing Salt and Calcium Magnesium Acetate Comparing Salt and Calcium Magnesium Acetate -- Special Report 235 (1991) / Chapter Skim
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4 Road Salt Impacts on the Environment 69 Vegetation, 69 Surface Water , 77 Soil, 80 Hypothetical Sites, 82 Summary, 92 5 Road Salt Impacts on Drinking Water 99 Relevance of Salt to Health, 99 Road Salt Concentrations in Drinking Water, 103 Mitigation Measures , 105 Cost, 108 Summary, 110 6 Calcium Magnesium Acetate 113 Discovery and Development, 113 Field Experience, 115 Health and Environmental Effects, 123 Compatibility with Automotive and Highway Materials, 129 Production Technologies and Price, 134 7 Summary of Cost and Use Issues 139 Road Salt Costs, 139 CMA, 148 Cost and Use Issues, 152 Outlook for Reducing Deicing Costs, 156 Appendix A State Highway Agency Questionnaire 159 Study Committee Biographical Information 165 x
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Executive Summary Each year about $1.5 billion is spent on highway snow- and icecontrol programs in the United States. Apart from plowing, the most important element of these programs is chemical deicing, which represents about one-third of winter maintenance expenditures.
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2 HIGHWAY DEICING the true cost of salting, which was last estimated 15 years ago for the Environmental Protection Agency. In addition, the committee reviewed what is known about CMA as a deicer and identified major cost and use issues that need to be addressed when CMA is considered as a replacement for salt.
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Executive Summary 3 cosmetic corrosion has been greatly reduced. Today the most clearly identifiable cost of road salt is the more expensive corrosion-resistant materials and coatings used in new cars and trucks.
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I 4 HIGHWAY DEICING currently sound decks that become damaged by continued salting will be about $125 million to $325 million per year. Bridge components other than concrete decks that are vulnerable to salt-induced damage include reinforced concrete supports (e.g., beams)
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Executive Summary 5 repair and maintenance requirements due to corrosion (from numerous sources) and other sources ·of damage are serious problems with large annual costs.
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6 HIGHWAY DEICING cost ranging from approximately $2 billion to $4.5 billion per year. Inclusion of other cost items that are based heavily on committee judgment provides a more complete, although less precise, cost estimate ranging from approximately $3.5 billion to $7 billion per year.
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Executive Summary 7 and that common roadside shrubs and grasses tend to tolerate salt better than do trees . Soil Salt's effect on soil is usually confined to 15 ft of the pavement edge.
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8 HIGHWAY DEICING not reflect the value of the injured tree to society or other indirect costs, such as diminished roadside aesthetics and secondary effects on the roadside ecosystem. Drinking Water Road sait can enter drinking water suppiies by migrating through soil into groundwater or by runoff and drainage directly into surface ~water.
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Executive Summary 9 CMA Since 1980, numerous laboratory and field studies have been conducted to evaluate CMA's field performance, likely impacts on the environment and human health, compatibility with automotive and highway materials, and prospective production technologies and market price. Findings from published reports of CMA field evaluations and interviews with current CMA users indicate the following: • Field experience: To date, CMA has had limited use, which complicates efforts to determine its likely performance under a wide range of conditions.
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From page 18... ...
10 HIGHWAY DEICING tually all automotive metals, plastics, coatings, parts, and components tested in laboratory experiments have exhibited fewer negative reactions when exposed to CMA than when exposed to salt. The potential for CMA spray to adhere to vehicle windshields and body parts, which has been reported by some field users, would probably require further study before more widespread use.
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Executive Summary 11 have little effect on the corrosion of many older, salt-contaminated infrastructure components or on many other costs related to corrosion prevention. Even in the absence of road salt, the continued corrosivity of the highway environment due to atmospheric pollution (acid precipitation)
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12 HIGHWAY DEICING materials, and other measures to mitigate salt's adverse effects. This is especially true for environmentally sensitive areas, because each roadside has a unique environment and valuations of environmental damage vary by location.
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1 Introduction The year-round use of the highway system is both expected by the public and essential to the national economy, causing many highway agencies to use large amounts of deicing chemicals to keep roadways free of winter snow and ice. The most widely used deicing chemical is sodium chloride, or common road salt, 1 which, because of its low price, easy application, and reliable ice-melting performance, has been a primary element of snow- and ice-control programs for many years.
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14 HIGHWAY DEICING cated that the total cost of highway deicing by salt exceeded $3 billion per year, or about 15 times the amount spent purchasing and applying salt each winter (Murray and Ernst 1976)
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Introduction 15 on findings from a survey of state highway agencies conducted for the study (see Appendix A)
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2 Road Salt Use in the United States Under many snow and ice conditions, the use of deicing chemicals is necessary to maintain clear pavements. In terms of 1 both time and budget, common salt, or sodium chloride, is widely regarded as the most effective means of deicing highways.
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18 HIGHWAY DEICING After World War II, as the expanding highway system became essential to the public and the national economy road salt use began to soar. The bare-pavement concept, under which motorists could expect snow- and ice-free pavements shortly after storms, soon became a policy in most cities and their suburbs.
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Road Salt Use in the United States 19 SALT APPLICATION AND STORAGE Early in the century, when salt was used selectively on busy city streets, it was often shoveled from the back of trucks. As its use grew, innovations were made in salting equipment and practices.
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20 HIGHWAY DEICING and highways, such as multilane freeways, are typically treated most intensely, through higher application rates and more frequent treatment. Lower-priority streets and secondary roads are often left untreated for longer periods, or not treated at all (see Figure 2-2)
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FIGURE 2-2 Top: Primary highway. Middle: Secondary highway.
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22 HIGHWAY DEICING TABLE 2-1 OFFICIAL SALT USE POLICIES IN VARIOUS STATES Region and State New England Connecticut Massachusetts Middle Atlantic Maryland West Virginia Great Lakes Michigan Ohio Wisconsin Plains Iowa Kansas West Colorado California Summary of General Policy Salt applied at 215 lb/lane-mi on multilane roads; no more than 150 lb/lane-mi on two-lane state highways Salt applied at less than 300 lb/lane-mi on state highways <;::o:ilt -:i.ru"\l~ro-:it~n.n rn1~rlf3l~np.
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TABLE 2-2 A VERA ON STATE HJG WA~ NORMALLY APPUEi=> Region and State New England Maine Massachusetts New Hampshire Vermont Middle Atlantic Delaware Maryland New Jersey New York Virginia West Virginia Great Lakes Illinois Indiana Michigan Ohio Wisconsin Plains Iowa Minnesota Missouri Nebraska Oklahoma South Dakota Mountain and West Alaska California Idaho Nevada New Mexico Road Sall Use in the United States 23 ANNUAL SALT LOADINGS WHERE SALT IS Average Annual Loading (tons/lane-mile) 8.0 19.4 16.4 17.1 9.0 7.1 6.7 16.6 3.0 6.3 6.6 9.0 12.9 9.1 9.2 3.8 5.0 1.0 1.5 1.5 1.0 1.2 3.0 0.3 1.9 0.5 NoTE: Data are from only those states that responded to relevant qttestions in survey.
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24 HIGHWAY DEICING FIGURE 2-3 I Iighw<1 y maint nanc yard. Top: Salt hopper and spreader truck.
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TABLE 2-3 ROAD MILEAGE CLASSIFIED BY FEDERAL-AID SYSTEM AND JURISDICTION (FHWA 1989, 114-116) Federal-Aid System Mileage Interstate and Other Secondary Non-Federal-Aid Total Jurisdiction Primary (Rural)
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26 HIGHWAY DEICING County 15% Total Salt Use • 10 million tons State 45% Municipal 35% Tolls 5% FIGURE 2-4 Salt use by jurisdiction (source: state survey and Salt Institute)
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Pacific West FIGURE 2-6 Definition of regions. SPENDING ON ROAD SALT Road Salt Use in the United States 27 Upper Mlddle AUenllc The average price of salt is approximately $30 per ton delivered.
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28 HIGHWAY DEICING Annual Spending by States • $750 million Ma11power 40% Abrasives/Other 10% Deicing Chemicals 20% Fr URE 2-7 State spending on snow and ice control by t rpe of expenditure (source: state survey and Salt Institute)
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Road Salt Use in the United States 29 or practices that threaten to reduce these benefits often arouse public concern and opposition. MANAGING ROAD SALT Whereas salt is an effective snow- and ice-control tool, its limitations require careful management.
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30 HIGHWAY DEICING management practices, equipment, and spreading techniques have improved both the effectiveness and the efficiency of many salting programs.
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3 Effects of Road Salt on Motor Vehicles and Infrastructure Road salt's impacts on motor vehicles and infrastructure are examined in this chapter. The focus is on three major areas: motor vehicles, bridges, and parking garages.
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32 HIGHWAY DEICING FIGURE 3-1 Top: Structural corrosion (perforations)
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Effects of Road Salt on Motor Vehicles and lnfrasrructure 33 dissimilar metals contact)
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34 HIGHWAY DEICING sea spray, calcium chloride, and road salt are greatest. Other corrosive environments are in the southern coastal areas of Florida and the Gulf Coast, where salt from sea spray, high humidities, and warm temperatures are especially conducive to corrosion.
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Effects of Road Salt on Motor Vehicles and Infrastructure 35 • Resin sealers for insulating body joints and crevices; • Design configurations that reduce entrapment areas and improve the ease with which protective coatings can be applied; and • New manufacturing technologies, such as more reliable robotics and adhesively bonded panels. These advances and others are now used widely by most manufacturers of cars and trucks sold in the United States and Canada.
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36 HIGHWAY DEICING of many of these improvements. Today the stated goal of the industry is to eliminate all exterior surface rust on new vehicles for at least 5 years and perforations for at least 10 years (Piepho et al.
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TABLE 3-2 CORROSION WARRANTY COVERAGE BY MAJOR AUTOMOBILE MAKERS, 1990 MODELS (Automotive News, 1989) Corrosion Coverage Make or Model (years or miles)
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38 HIGHWAY DEICING increased the cost of manufacturing vehicles. In response, the cost items listed were primarily special paints, coatings, and materials.
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Effects of Road Salt on Motor Vehicles and Infrastructure 39 vehicles longer and demand long-term protection from all types of corrosion and premature wear. Estimates of savings in the cost of corrosion protection that would result from reductions in salt use vary depending on the importance ascribed to these other considerations.
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40 HIGHWAY DEICING T .ABLE 3-3 PERCENTAGE OF SURVEYED VEHICLES WITH RUST DEFECTS (Bryant et al.
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Effects of Road Salt on Motor Vehicles and Infrastructure 41 Cost of Persistent Corrosion Murray and Ernst, in their 1976 economic analysis of the environmental impact of road salt conducted for the Environmental Protection Agency, estimated that the cost of salt-related vehicle corrosion, including corrosion protection, was about $2 billion per year (in 1975 dollars) (Murray and Ernst 1976)
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42 HIGHWAY DEICING $1 billion to $2 billion per year (9 million vehicles x $125 to $250 per vehicle = $1.1 billion to $2.2 billion)
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Effects of Road Salt on Motor Vehicles and Infrastructure 43 Crack Concrete Rebar Corrosion lack full shoulders, even minor irregularities and potholes can result in hazards that require prompt repair. Bridge Deck Repair and Rehabilitation Conventional methods of deck repair range from patching of individual potholes during early stages of deterioration to complete deck replacement if potholes and patches cover a large portion of the deck.
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44 HIGHWAY DEICING FIGURE 3-5 Patching of a severely contaminated conuete deck. reached, deck deterioration usually continues, regardless of the subsequent use of salt or noncorrosive deicers.
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Effects of Road Salt on Motor Vehicles and Infrastructure 45 states that are already severely damaged or critically contaminated with chloride. 3 Repair and Rehabilitation Costs According to the National Bridge Inventory, about 55 percent of concrete decks in the United States are in sound condition and not already critically contaminated with chlorides.
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TABLE 3-5 ESTIMATED NUMBER OF DECKS THAT WILL BE DAMAGED BY CONTINUED SALTING DURING NEXT 10 YEARS No. of Undamaged Decks Damaged During Current Next 10 Years No.
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Effects of Road Salt on Motor Vehicles and Infrastructure 47 deterioration in the low-salt regions of the South and West are used instead, one would expect only about 5 percent, or approximately 3,000, to be damaged (Table 3-5)
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48 HIGHWAY DEICING that they routinely use some type of protective s"ystem on bridges built where road salt is used. By far the most common is epoxycoated reinforcing steel, the use of which is standard in 25 states.
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Effecls of Road Salt on Motor Vehicles and Infrastruc1ure 49 cost x 20 million to 30 million ft 2 of deck surface, rounded to the nearest $25 million)
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50 HIGHWAY DEICING ped or ponded water, which can be hazardous to traffic and contribute to deterioration of the bridge understructure. Most drajnage systems use metal pipe that funnel water from tb deck to th ground.
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Effects of Road Salt on Motor Vehicles and Infrastructure 51 detected before it becomes a serious hazard. Repairs are made by removing the rust and applying a protective paint or coating or by replacing the rusted steel section with metal plating.
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FIGURE 3-6 Concrete spalling on bridge structure.
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Effects of Road Salt on Motor Vehicles and Infrastructure 53 sioning of steel strands in the concrete. Because several prestressed segments can be strung together with minimal intermediate support, this design is popular for long-span bridges crossing stretches of rough terrain, bodies of water, and congested urban areas.
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54 HIGHWAY DEICING prestressed concrete bridges eventually be discovered, the total cost would be considerably higher. Summary of Impacts on Other Bridge Components In addition to decks, components of bridges that are vulnerable to salt damage include concrete supports, steel framing, bearings, and joint devices.
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Effects of Road Salt on Motor Vehicles and Infrastructure 55 Road salt can exacerbate this problem, both by increasing freezethaw cycles and by forming expanding crystals in the concrete. This effect is no longer a serious .concern for most highway agencies, however, because air entrainment has been a standard construction practice for many years.
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56 HIGHWAY DEICING and gutters. Because drainage systems account for about 10 percent of highway construction and maintenance expenditures and are important to highway operations and safety, their performance and durability are critical (TRB 1978, 3)
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Effects of Road Salt on Motor Vehicles and Infrastructure 57 vandalism, obsolescence, and vibrations from traffic (American Public Works Association 1985)
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58 HIGHWAY DEICING PARKING GARAGES According to estimates from Census Bureau data, there are about 10,000 multilevel parking garages in the United States. About half are located in the salt-using regions of the Northeast and Midwest.
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Effects of Road Salt on Motor Vehicles and Infrastructure 59 TABLE 3-7 IN REMENTAL CO T OF VARIOUS PARKING STRU '"J'lJRE REPAIRS (Tighe and Van Volkinburg 1989, 71) Repair Option Patching and sealing Patching and membranes Conventional concrete removal and replacement with high-performance overlaY Cost ($/ft2)
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60 HIGHWA y DEICING imately $1 million ($7.50 x 150,000 ft2) , and the cost of repairing 50 to 150 per year is $50 million to $150 million.
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£/feels of Road Sall on Mo/or Vehicles and lnfrastruclure 61 UNDERGROUND OBJECTS Corrosion damage to utility lines, pipelines, and steel storage tanks buried under or alongside highways is sometimes attributed to the use of road salt, especially in urban areas, which have a high density of underground utility lines and heavy salt usage. Altogether, the United States has about 2 million mi of natural gas and water distribution lines and service laterals (TRB 1988, 14)
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62 HIGHWAY DEICING valve components (e.g., stainless steel bolting on valves) (personal communication, American Water Works Association)
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Effects of Road Salt on Motor Vehicles and Infrastructure 63 SUMMARY OF COSTS Great strides have been made in the past 10 years in reducing the adverse side effects of salting by protecting motor vehicles and infrastructure from corrosion. Advances are continuing, and the outlook for further reductions in damage is promising.
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64 HIGHWAY DEICfNG able, such as persistent motor vehicle corrosion and damage to highway components, can be approximated only on the basis of committee judgment and conjecture to provide a rough sense of scale (Category II)
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Effects of Road Salt on Motor Vehicles and Infrastructure 65 agencies as a possible concrete rehabilitation treatment for the future (Broomfield and Jawed 1990; Manning and Pianca 1991)
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66 HIGHWAY DEICING Bennet, L., J Kruger, R
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Effects of Road Salt on Motor Vehicles and Infrastructure 67 TRB.
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4 Road Salt Impacts on the Environment Hundreds of reports have been written during the past three decades documenting the impact of road salt on the environment. The literature clearly indicates that the impacts can be significant but depend on a wide range of factors unique to each site.
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70 HIGHWAY DEICING Investigations of salt's impact on vegetation were conducted during the 1960s and 1970s in New Hampshire, Minnesota, Michigan, and several other snowbelt states, usually in response to concerns about damage to roadside trees (Lacasse and Rich 1964; Sucoff 1975; Bowers and Hesterberg 1976; Scharpf and Srago 1975)
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Road Salt Impacts on the Environment 71 of the plant may result because of the added weight of the salt deposit, but tissue damage due to local dehydration is more common (Wilcox 1984; Bowers and Hesterberg 1976; Foster and Maun 1978)
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72 HIGHWAY DEICING • Temperature: The effects of salt are compounded by higher temperatures, which cause increased dehydration through foliage, faster movement of salt to the plant, and increased salt absorption through roots. • Light: Exposure to direct light increases the rate of dehydration.
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Road Salt Impacts on the Environment 73 trees tend to retain less chloride as a percentage of tissue weight. Table 4-1 gives 12 species of salt-tolerant trees and 10 species of intolerant trees (Shortle and Rich 1970)
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TABLE 4-1 SALT TOLERANCE IN COMMON ROADSIDE TREES (Shortle and Rich 1970)
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Road Salt Impacts on the Environment 75 flowering and the dieback of shoots that are associated with increased levels of sodium and chloride in twigs. Chloride accumulation in tree tissues was found to increase from February to April, during the peak salting season.
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76 HIGHWAY DEICING scaping (Cordukes 1968)
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Road Salt impacts on the Environment 77 For many situations, however, redesign of roadsides is not practical. As a result, most highway agencies are faced with three options: acceptance of some salt-related damage to roadside vegetation, discontinuance or restriction of salt treatments in especially sensitive areas, or use of a deicing substitute with fewer side effects than salt (Hanes et al.
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78 HIGHWAY DEICING enter larger water systems. For example, Schraufnagel found chloride concentrations higher than 10 000 mg/L in spring runoff in Wisconsin, yet the maximum concentration in adjacent surface waters was only 45 mg/L (Schraufnagel 1965)
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Road Salt Impacts on the Environment 79 Lakes and Ponds Some correlation has been found between salting activity and higher sodium and chloride concentrations in lakes and ponds. However, unlike small streams and creeks, ponds and lakes are often recharged by a large and varied watershed (including groundwater)
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80 HIGHWAY DEICING and Judd 1972)
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Road Salt lmpacls on the Environment 81 Sand, gravel, and coarse-textured soil allow fast infiltration, whereas clay and fine-textured soil slow infiltration (Jones et al.
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82 HIGHWAY DEICING roadside soils were similar to those in nonhighway locations (Pilon and Howard 1987)
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I Application of salt I to highway t t Salt remains on I I Splashed. sp |
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Road Salt Impacts on the Environment 85 Forest Trees Salt damage to roadside trees typically occurs as a result of (a) salt accumulation in soil, (b)
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86 HIGHWAY DEICING is approximately $500. Multiplication of $500 by the estimated 10 to 25 trees per year that might die on this site yields a cost of tree removal and replacement of $5,000 to $12,500.
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Road Salt Impac1s 0 11 the Environment 87 Site 2 Site 2 consists of deciduous, coniferous, or mixed forest trees adjacent to a 1-mi section of a two-lane rural (or secondary) highway with open drainage.
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88 HIGHWAY DEICING vehicle speeds, traffic levels, and salt loadings result in even less salt being deposited on the roadside, reducing the frequency of gypsum treatments and other mitigation measures. Treatment once every 10 years yields an average annual cost of $250 (see discussion of Site 1)
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Road Salt Impacts on the Environment 89 aquatic life, and, therefore, reduction in salt use or changes in highway drainage may be necessary for stream recovery (Bubeck et al. 1971; Diment et al.
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90 HIGHWAY DEICING topography is assumed, resulting in no significant potential for erosion damage. Damage to soils, if any, is covered in the discussion of Site 1.
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Road Salt Impacts on the Environment 91 Site 5 Site 5 consists of a maintenance yard adjacent to a highway bordered by a residential area and forest trees and shrubs. The maintenance yard is assumed to contain uncovered salt stockpiles.
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92 HIGHWAY DEICING TABLE 4-3 ROAD SALT DAMAGE TO FRUIT CROPS FOR SITE 6 (Bacchus 1987) Full Value of Crop• Percent of Value of Loss Type of Crop ($/acre/year)
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Road Salt Impacts on the Environment 93 regions of the country, especially in forests and parklands adjacent to highways. Trees and other roadside vegetation can be injured by salt through changes in soil chemistry and from salt splash and spray on foliage and branches.
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94 HIGHWAY DEICING were not intended, nor can they be accurate enough, to compare the overall cost of salt with that of other deicing chemicals. Meaningful estimates of the cost of environmental damage can be accomplished only for individual sites, whereby local circumstances can be evaluated in depth.
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Road Salt Impacts on the Environment 95 Berthouex , P
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96 HIGHWAY DEICING Goldman , S
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Road Salt Impacts on the Environment 97 Kenaga, D
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98 HIGHWAY DEICING Schraufnagel F
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5 Road Salt Impacts on Drinking Water Many studies during the past 30 years have linked increased salt concentrations in drinking water with highway salting operations. Concerns about road salt as a potential contaminant in drinking water date back to the 1950s, when it was discovered that salt was contaminating drinking water supplies because of improper storage and, in some cases, highway runoff.
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100 HIGHWAY DEICING is necessary for the body and cells to regulate fluids and for the transmission of electrical impulses in the nervous system and muscles (NRC 1989b, 413)
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TABLE 5-1 PERCENTAGE CONTRIBUTION OF MAJOR FOOD GROUPS TO DAILY INTAKE OF SODIUM (Pennington and Young 1991) " Age and Sex Group (%)
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102 HIGHWAY DEICING Sodium Concentrations in Drinking Water Sodium concentrations in drinking water are variable . For example, a study conducted by the U.S.
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Road Salt Impacts on Drinking Water 103 daily. AHA has no position on sodium concentrations in drinking water for the general public.
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104 HIGHWAY DEICING spring thaws can produce high concentrations of salt. For example, meltwater samples near several large snowbanks in Wisconsin contained sodium concentrations exceeding 1000 mg/L (Schraufnagel 1965)
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Road Salt Impacts on Drinking Water 105 after the program began, average sodium concentrations in the wells dropped by more than 50 percent, from 79 to 36 mg/L (Pollock 1990)
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106 HIGHWAY DEICING Though it appears that most egregious salt storage problems are now being corrected, during the past 20 years concerns about the potential for salt contamination of water from highway runoff have increased (Murray and Ernst 1976, 14)
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TABLE 5-2 DISPOSITION OF ROAD SALT CONTAMINATION COMPLAINTS BY PRIVATE WELL OWNERS IN MASSACHUSETTS, 1982-1988 (Pollock 1988) Public Annual Well Supply Water Drainage Salt Expenditure for Year Replacement Connection Treatment Change Substitute Other Fiscal Year (S)
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108 HIGHWAY DEICING for example, 34 wells with sodium concentrations exceeding 20 mg/L were connected to public water systems at a cost of $430,000, or about $13,000 per complaint. Well replacement (whereby wells are drilled deeper and carefully sealed)
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Road Salt Impacts on Drinking Water 109 ever, the nine states apply about one-half of all salt used by states, and their reports are useful reference points for estimating nationwide spending on prevention and remediation. All nine statesIllinois, Indiana, Maine, Massachusetts, Michigan, New Hampshire, New York, Pennsylvania, and Vermont-are located in the northeastern and central United States, where concerns about salt contamination of drinking water are greatest.
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110 HIGHWAY DEICING with a health risk to the general public. As a result, no attempt was made in this study to estimate public health risks and costs.
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Road Salt Impacts on Drinking Water 111 cipally because of the uncertain effects of salt on health. As a result, no attempt was made in this study to estimate other costs of salting, if any, that might be related to public health.
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112 HIGHWAY DEICING Pollock, S
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6 Calcium Magnesium Acetate What is known about calcium magnesium acetate (CMA) is reviewed in this chapter.
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114 HIGHWAY DEICING closer to that of salt. Whereas both chemicals were deemed suitable from the standpoint of a number of deicing criteria, CMA was selected for continued development because of its greater environmental acceptability and handling and spreading characteristics that more closely resembled those of salt.
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Calcium Magnesium Acetate 115 The primary producers of CMA at the time-Chevron Chemical Company, Verdugt, Inc. (Netherlands)
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116 HIGHWAY DEICING melting capacity is not the only characteristic important to deicing. As the following results from field tests indicate, chemical deicing also involves ice prevention, penetration, disbanding, and interactions with traffic and weather.
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Calcium Magnesium Acetate 117 CMA was applied in quantities ranging from 1.2 to 1.6 times greater than those of salt. At these rates its deicing performance was comparable with that of salt.
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From page 126... ...
118 HIGHWAY DEICING Depending on storm conditions, CMA was applied in quantities ranging from 1 to 3 times those of salt, but typical amounts were between 1.3 and 1.8 times greater. By experimental design, the frequency of application did not vary by deicer.
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Calcium Magnesium Acetate 119 back to salt. At temperatures above -5°C (23°F)
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120 HIGHWAY DEICING Each of these users was contacted for this study and asked about CMA's performance. Most comments concerning CMA's deicing effect were similar to those from reports cited previously.
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From page 129... ...
Calcium Magnesium A cetate 121 However, because dusting tended to increase during prolonged storage (periods exceeding 6 weeks) , well-ventilated storage facilities were recommended.
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122 HIGHWAY DEICING equipment and adhere to truck beds. Several reported that CMA spray occasionally stuck to the windshields of passing cars.
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Calcium Magnesium Acetate 123 although CMA was sometimes applied less frequently during longer storms. Several highway agencies found that early application (i.e., at the outset of the storm, before significant snow and ice accumulation)
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124 HIGHWAY DEICING Transportation (Caltrans) and the National Cooperative Highway Research Program (NCHRP)
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Calcium Magnesium Acetate 125 conducted to investigate impacts on metals in roadside soils and to track environmental effects over an extended period of time. NCHRP Study Following completion of the Cal trans study, researchers at the University of Washington embarked on an NCHRP-sponsored study (Horner 1988)
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From page 134... ...
126 HIGHWAY DEICING • Vegetation: Various applications of CMA to vegetation by spraying and flooding did not affect the yield, cover, vigor, or rooting of various herbaceous and woody plants. All species tested withstood root zone applications of up to 2500 mg/L.
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Calcium Magnesium Acetate 127 • Chevron Chemical Company (Hiatt et al.
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128 HIGHWAY DEICING • The effect of CMA on soil metals was also investigated by Amrhein and Strong (1990)
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Calcium Magnesium Acetate 129 salt to reach groundwater. CMA has demonstrated no detrimental effects on soil compaction or strength, and it may increase the fertility and permeability of some roadside soils.
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130 HIGHWAY DEICING Major findings were as follows: • Paints, coatings, and adhesives: Automotive paints and coatings exposed to CMA exhibited some breakdown, but the same specimens exposed to salt exhibited more severe effects. Neither salt nor CMA affected adhesives.
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From page 139... ...
Calcium Magnesium Acetate 131 beams, and rebars. A study by the state of Michigan compared the effects of CMA and salt on many of these applications (McCrum et al.
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132 HIGHWAY DEICING (active) corrosion potential.
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Calcium Magnesium Acetate 133 Other Highway Materials The most comprehensive investigation of CMA's compatibility with highway materials was conducted by Slick (1987)
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From page 142... ...
134 HIGHWAY DEICING and body parts, which has been reported by some field users, would probably require further study before more widespread CMA use. Laboratory tests also indicate that CMA is less detrimental than salt to common highway materials, including those used for paving, road marking, and construction.
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From page 143... ...
Calcium Magnesium Acetate 135 wastes, such as dairy whey and pulp and paper mill sludges. Preliminary engineering and economic analyses based on the use of dairy whey as a feedstock projected an ultimate CMA price of $280 per ton (Leuschner 1988)
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From page 144... ...
136 HIGHWAY DEICING NOTES 1. Environmental concerns about rneU1anol include its pot ntial volatility during handling and storage and its lethality to human.
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From page 145... ...
Calcium Magnesium Acerare 137 In The Environmental Impact of Highway Deicing (C.
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From page 146... ...
138 HIGHWAY DEICING Peart, J
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From page 147... ...
7 Summary of Cost and Use Issues Findings from Chapters 3 through 5 on the adverse side effects of road salt are summarized in this chapter. That discussion is followed by a review of what is known about the effects of calcium magnesium acetate (CMA)
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From page 148... ...
140 HIGHWAY DEICING Motor Vehicle and Infrastructure Costs (Chapter 3) Sodium chloride, as well as calcium chloride, can damage motor vehicles and infrastructure primarily because of the corrosive effects of chloride ions on metals.
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From page 149... ...
Summary of Cost and Use Issues 141 for the more than 15 million new vehicles purchased each year in the United States is between $1.9 billion and $3.9 billion (15.4 million new vehicles x $125 to $250)
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From page 150... ...
142 HIGHWAY DEICING has increased the cost of constructing a new deck by about $4/ft2. Between 20 million and 30 million ft2 of new deck surface is constructed each year in the Northeast and Midwest; hence, annual spending on deck protection is about $75 million to $125 million ($4/ft2 x 20 to 30 million ft2, rounded to the nearest $25 million)
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From page 151... ...
Summary of Cost and Use Issues 143 Other Highway Components Apart from bridges, components of the highway system adversely affected by road salt include concrete pavements, highway drainage systems, and roadway fixtures and accessories (such as metal light stands, signposts, and guardrails)
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From page 152... ...
144 HIGHWAY DEICING the United States are equipped with some type of protective system, such as epoxy-coated re bars and a denser and thicker concrete cover. The total cost of installing protection on new parking garages is about $25 million per year.
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From page 153... ...
Summary of Cost and Use Issues 145 exposed to traffic-generated salt splash and spray. Because the severity and extent of damage depend on local circumstances-such as salt usage, the number of roadside objects, and the presence of other corrosion sources-it is not possible to quantify this damage on a national basis.
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From page 154... ...
146 HIGHWAY DEICING growth, browning and falling needles and leaves, and sometimes dying limbs and premature plant death. Under extreme conditions (e.g., high winds)
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From page 155... ...
Summary of Cost and Use Issues 147 Surf ace Wat er Salt's effects on surface water are confined mainly to small streams and creeks running adjacent to heavily salted highways. Small receiving lakes and ponds can also be adversely affected, but few such incidents have been reported.
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From page 156... ...
148 HIGHWAY DEICING During the past 30 years, communities in several states, primarily in the Northeast, have reported higher sodium and chloride concentrations in private wells and public water supplies that have been linked to road salt. Many of these problems have been caused by improper salt storage.
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From page 157... ...
Summary of Cost and Use Issues 149 relative to salt. Most users reported that it worked adequately but not quite as effectively or in quite the same manner as salt.
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From page 158... ...
150 HIGHWAY DEICING field reports indicate that dusting and blowing were less troublesome than reported in pre-1985 field trials , though in many cases protective dust masks and truck covers were still required during handling and spreading activities. CMA had to be kept dry during storage, usually in enclosed and well-ventilated shelters.
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From page 159... ...
Summary of Cost and Use Issues 151 paper mill biomass, could introduce contaminants that alter its known environmental effects or create new ones. Compatibility with Motor Vehicles and Highway Materials CMA is much more compatible with automotive materials and components than is salt.
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From page 160... ...
152 HIGHWAY DEICING production processes, CMA prices on the order of $600 to $700 per ton are the only reasonable projections that can now be made. COST AND USE ISSUES As a means of identifying some of the important cost and use issues that must be addressed when considering conversion to CMA, three general situations are discussed.
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From page 161... ...
Summary of Cost and Use Issues 153 Widespread use of CMA would benefit aspects of the roadside environment and possibly the quality of drinking water in some communities. Most research indicates that CMA has less severe impacts than salt on the environment and water quality except in certain controllable situations.
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From page 162... ...
154 HIGHWAY DEICING CMA's greater quantity requirements suggests that nearly twice as much storage space and truck capacity would be required (1.2 times more CMA tonnage x 1.6 times greater volume per ton = 1.92 times more volume per ton of salt replaced)
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From page 163... ...
Summary of Cost and Use Issues 155 challenged by CMA's limited versatility compared with alt. Coniderably more spending on deicing material equipment and manpower would be necessary even for local use.
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From page 164... ...
156 HIGHWAY DEICING Table 7-1. Numerou a umptions are required, including the Liming and cost of deck .repair if salting continue ; the quantity of CMA required to achieve acceptable deicing; and attendant CMA storage handling and spreading cost .
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From page 165... ...
TABLE 7-1 HYPOTHETICAL USE OF SALT AND CMA FOR HIGHWAY STRUCTURES AND COMPARATIVE COSTS Continued Salting: Conversion to CMA: Present Value Present Value Costb ($ millions) Coste ($ millions)
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From page 166... ...
158 HIGHWAY DEICING consideration other deicers and mitigation measures available. CMA's use and acceptance is likely to depend in large part on the progress made in these other areas.
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From page 167... ...
APPENDIX A State Highway Agency Questionnaire Name of Respondent _ ____ _ State - - -- -- -Title -- -- - -- -- -- - Phone ___ _ __ ~ SURVEY OF DEICING CHEMICAL USAGE AND MITIGATION MEASURES 1. Does your agency use chloride deicing salts (sodium chloride or calcium chloride)
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From page 168... ...
160 HIGHWAY DEICING 3. Please specify the approximate minimum, maximum, and average salt usage on state-maintained highways in terms of annual tons per lane-mile (by highway type if possible)
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From page 169... ...
State Highway Agency Questionnaire 161 [ ]
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From page 170... ...
162 HIGHWAY DEICING Is the annual number of complaints increasing?
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From page 171... ...
State Highway Agency Questionnaire 163 If upward, by how much since 1980? ______ % If downward, by how much since 1980?
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From page 173... ...
Study Committee Biographical Information John J Henry, Chairman, is Director of the Pennsylvania Transportation Institute and Professor of Mechanical Engineering at The Pennsylvania State University .
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From page 174... ...
166 HIGHWAY DEICING Directors of ASTM and the National Association of Corrosion Engineers (NACE)
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From page 175... ...
Study Committee Biographical Information 167 received his bachelor's degree in biology from the University of California at Davis and his master's degree in biology from California State University at Sacramento. He began his career in the department as an Environmental Planner.
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From page 176... ...
168 HIGHWAY DEICING ican Chemical Society and the American Society of Engineering Education. David G
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From page 177... ...
S1udy Committee Biographical Information 169 he has worked at the GM Proving Ground in the Corrosion Technology Center to develop corrosion-resistant designs and material and processing criteria and to evaluate corrosion performance. Samuel J
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From page 178... ...
170 HIGHWAY DEICING eastern University in 1987, he was Vice President and Manager of the Biotechnology Department of Dynatech R&D Company. He began his career as an Assistant Professor of Engineering at Widener College in Pennsylvania.
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Key Terms
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