Dust Suppression on Wyoming’s Coal Mine Haul Roads

Dust Suppression on

Wyoming’s Coal Mine

Haul Roads

Literature Review

Recommended Practices

and Best Available

Control Measures – BACM

Dust Suppressant

Selection Guides

A Manual

prepared for:

Industries of the Future

Converse Area

New Development

October, 2004

by:

Temple Stevenson

i

TABLE OF CONTENTS

Introduction iii

I. Literature Review: Fugitive Dust and Its Control 1

II. Recommended Practices and Best Available

Control Measures 21

Table 2.1 Dust Control Operations Recommendations 25

Figure 2.1 Sample Air Event Outline 26

Table 2.2 Best Available Control Measures

BACM (Recommendations) For Controlling

Fugitive Dust on Mine Haul Roads 28

III. Dust Suppression Selection Guides 31

Table 3.1 Dust Suppression Products 33

Table 3.2 Dust Suppression Applications Guide 41

Table 3.3 Dust Suppression on Mine Haul Roads

Cost Worksheet (available in excel) 57

Appendices 61

Appendix A: Dust Suppression Survey and Results 63

Appendix B: Dust Control Plan and

Self Inspection Checklists 67

Appendix C: Palliative Selection Matrix

(Thompson) 73

Appendix D: Palliative Selection Matrix

(Bolander and Yamada) 77

Introduction

Fugitive dust emissions are increasingly becoming a problem for Wyoming’s surface coal mines located in a windy semi-arid environment where the average wind speed is 13.4 miles per hour and the average rainfall is a mere 14 inches with some of the highest evaporation rates in the nation. Fugitive dust emissions are a nuisance in coal mines; dust impairs visibility, affects the health of employees, increases wear and tear of equipment, and increases road maintenance and costs. Current drought conditions, elevated wind speeds, compliance with air quality and clarity standards impacted by particulate emissions, a predicted increase in coal production, and increased Coal Bed Methane operations has heightened the concern.

Dust from surface coal mine operations also has the potential to negatively impact Federal Class I Air Quality Areas in the region, such as Badlands and Wind Cave National Parks and the Northern Cheyenne American Indian Area. While no visibility impairment in these Class I areas is currently attributable to any Wyoming source, it is anticipated that strategies to maintain a status of minimal impact will be of notable value to the Western Regional Air Partnership (WRAP) and the State of Wyoming in the development of its Regional Haze SIP(State Implementation Plan), due by Dec 31, 2008 (Wyoming’s Long Term Strategy for Visibility Protection: Review Report, 2003).

It is the intent of this report to contribute to a better understanding of fugitive dust and its mitigation, so that efficient and effective management strategies for suppressing it can be implemented. The report includes four segments: I. Literature Review; II. Recommended Practices and Best Available Control Measures -BACM; III. Dust Control Suppressant Selection Guides; and an Appendices containing a fugitive dust bibliography and document examples.

I. Literature Review: Fugitive Dust and its Control

Sources and Impact of Dust Generated by Surface Coal Mines Haul roads, over-burden piles, drilling and blasting, coal transfers and loading, and topsoil handling are all contributing factors of dust generation in a coal mine. A South African study conducted in an arid climate similar to Wyoming’s by Thompson and Visser (2002) titled “Benchmarking and Management of Fugitive Dust

Emissions From Surface Mine Haul Roads,” determined that 93% of the total dust

emissions from a coal strip mine could be contributed to coal transport or haul roads. Figure 1. illustrates their findings of the contributions of specific sources of fugitive dust as a percentage of the total fugitive dust generated by a surface coal mine.

93% of the total dust emissions from a coal strip mine could be contributed to coal transport or haul roads

Fig. 1 Percentage contribution to total dust emissions (Thompson & Visser 2002)

Assessing the source and impact of dust to determine the need to increase watering, decrease speed, use dust suppressing chemicals (also known as palliatives), or

re-graveling is constricted by a lack of problem solving methodology that takes into account the complexity of various interactions. The interactions include traffic volume, weight, climate, and more according to Thompson & Visser (2002). They add, “most surface mine operators agree that dust-free roads are desirable, but find it difficult to translate this into cost-effective management and mitigation.” This same study found that regular watering and the application of chemical suppressants in conjunction with optimal aggregate surfaces is the only effective option for controlling fugitive dust emissions on haul roads.

The most harmful types of fugitive dust to the respiratory system are those that are under 10 microns in diameter, known as PM10’s. Because they are most harmful, they are the

most monitored. Another common measurement involves total suspended particulates’ or TSP’s. Total suspended particulates refer to the total amount of solid particulates and liquid droplets suspended in the air, regardless of particle size (Ferguson et al., 1999). Wyoming has been monitoring PM10 emissions to meet Federal standards since 1989,

before that TSP’s were the only monitored emission.

According to EPA officials, exceedences of the 24 hour standard for particulate matter in southern Campbell County escalated substantially over the last 15 years; from 0 incidents during 1990-2000 to 19 incidents from 2001-03.

Dust Suppression Planning

When a coal mine is in the process of implementing a dust suppression plan, cost analysis plays a large role in product selection. When looking at a product, an overall cost analysis should be taken into account. According to Bolander and Yamada (1999) in a report for the US Forest Service entitled “Dust Palliative Selection and Application Guide,” a successful dust control program should not only reduce total dust emissions, but it should also reduce maintenance costs. Some dust control products have proven that they can significantly reduce overall road maintenance costs and thus achieve an overall savings. At the same time additional preparation and a change in maintenance practices must be accounted for. A booklet published by Environment Australia, a branch of Australia’s Department of the Environment and Heritage, Dust Control Best Practice Environment

Management in Mining (1998), explains the benefit of a dust control plan as “a long-term

view of dust control has proven consistently cost effective. Mine planning has a

particularly important role to play in dust control. Applying controls after the problems arise is often difficult, impractical or costly.”

Haul Roads/Unpaved Roads

Fugitive dust is derived from a variety of sources; nonpoint sources such as un-vegetated soils, and specific sources such as haul roads (Environment Australia 1998). Dust generation can be defined as the process by which particulate matter becomes airborne. The amount of dust that becomes airborne is a function of various factors; including the susceptibility of the surface material to wind and water erosion, and the erosive actions of haul trucks (Thompson & Visser 2002). If this latter human activity coincides with unfavorable weather conditions, the result can be greatly increased dust emissions (Ferguson et al., 1999).

Haul roads generate significant amounts of dust emissions (EPA Fugitive Dust, 1992; Thompson and Visser, 2002).

There have been several studies completed to estimate the emission rates of PM10 on

unpaved roads. According to Bolander and Yamada (1999) in the US

Forest Sevice Report, Dust Palliative Selection and Application Guide, the following dust generation factors should be considered when designing a dust control plan:

Dust Generation Factors: • Vehicle Speed

• Number of Wheels Per Vehicle • Traffic Volume

• Particle Size Distribution of the Aggregate • Compaction of the Surface Material • Surface Moisture

• Climate

Researchers from the Desert Research Institute at the University of Nevada determined that a vehicle traveling on a untreated unpaved road at a speed of approximately 25 mph generates between 0.59 to 2.00 lbs of PM10 emissions per vehicle miles traveled (VMT)

(Gillies et al. 1999). When that vehicle’s speed was increased to 35 mph the emission rates increased to 1.85 to 3.04 lbs. PM10 VMT with an uncertainty of 0.23 lbs. PM10

VMT. Other studies have found similar emission results. Flocchini et al.(1994) suggest that reducing vehicle travel speeds on unpaved roads from 40km/hr to 24 km/hr reduced PM10 emissions by 42 + 35%.

The Environmental Protection Agency, reporting in Compilation of Air Pollutants

Emission Factors Volume 1 Ch 13, AP-42 (1998), found that emission of fugitive dust on

haul roads is highly correlated with vehicle weight and silt content of the surface

material. The study reported that a silt content mean of 8.4% of fines on a haul road while a mean of 24% was found on a freshly graded haul road. This indicates a significant increase in fines after a road has been graded.

In addition to these factors the EPA also suggests that other traffic characteristics should be considered; such as the cornering of trucks, the road’s bearing strength, and grade (EPA, 1998, AP-42). They also suggest a complete examination into climate conditions like freeze/thaw cycles and monthly average wind speeds.

Effective dust control on haul roads in the Powder River Basin is complicated by the fact that stretches of road, constructed of less than optimal aggregates, are subject to high traffic volume by heavy haul trucks, which requires continuous grading and the frequent addition of new surface material. Wearing of surface material is related to a number of factors including wind speed at the road surface, traffic volume and tonnage, type of road aggregate, compaction of the road, amount of spillage, and climate (Thompson & Visser 2002).

In addition to haul roads and related travel areas such as truck parking lots,

stockpile/reclaim areas also contribute to total dust emissions, but are usually much more difficult to control. (EPA Fugitive Dust, 1992). The EPA has devised numerous

equations to estimate emissions both from unpaved roads and from storage piles. These equations can be found in “Fugitive Dust Background Document and Technical

Information Document for Best Available Control Measures,” published by the EPA in

In a report by the U.S Army Construction Engineering Research Laboratories Gebhart et al.(1999) noted that chemical suppressants should be considered as a secondary solution in controlling dust. “A properly maintained road with adequate drainage to create a hard road surface should be the first step and must be implemented to the greatest extent possible. The best way to avoid a dust problem is to properly maintain the surface, and that is achieved by grading and shaping for cross sectional crowning which prevents dust generation caused by excessive road surface wear.” It should be noted that this study had to contend with heavy vehicles with tracks, such as tanks, which reduced the efficiency and cost effectiveness of any dust suppressant.

Effectiveness of Dust Suppressant Measures on Unpaved Roads When analyzing dust control effectiveness it is hard to

determine a product’s direct impact due to the large number of compounding variables (traffic volume, truck weight and speed, road type, etc.). This is further compounded by the fact that there is not a uniform standard for determining dust suppressant effectiveness (North Carolina Department of Environment and Natural Resources Division of Air Quality (2003). Most assessments available are based on qualitative data not quantitative data (Sanders & Addo, 1993). “Without any quantitative dust measurement, it is difficult if not impossible to assess the economics and lasting value of dust palliation methods,” (Sanders & Addo, p.11, 1993). There are generally two areas of study concerning measuring or analyzing dust. The first is atmospheric modeling and

prediction, and the second is field measurements and quantifications (Sanders & Addo, 1993). Field studies are generally more helpful in determining actual effectiveness; however there are numerous factors that need to be considered. Because of the diversity of site characteristics, it is difficult to recommend a suppressant that will work well in all situations.

Chemical dust suppressants generally provide a PM10

control efficiency of about 80% when applied at regular intervals of two weeks to one month (EPA, AP-42, 1998). The effectiveness of dust suppressants however, depends on the dilution rate, the application rate, the time between applications, the amount, weight and speed of traffic, meteorological conditions, and road characteristics.

In many instances the only gauge of the effectiveness of a product is either the results from manufacturer’s testing or testimonials from previous users (Engle, 2004). Even then it is hard to determine if the product is going to work in a particular area with possibly a different aggregate type.

The following is a summary of some of the significant studies that have been conducted regarding the relative effectiveness of dust control measures.

Thomas Sanders, et al.(1997) conducted a study at Colorado State University on unpaved road sections in Larimer County, Colorado to try to determine the relative effectiveness of the three commercially available dust suppressants. These researchers evaluated the effectiveness of lignosulfonate (lignin’), calcium chloride (CaCl2), and magnesium

chloride (MgCl2) against a section left untreated. They based their evaluation on three

fundamental measurements; traffic volume, fugitive dust emissions, and total aggregate loss and used these measurements to calculate a cost analysis.

After taking 15 dust samples over a test period of 4.5 months they found that all three of the treated sections outperformed the untreated section. Total aggregate loss was

significantly higher for the untreated section, in fact it was 3 times more than the MgCl2,

2.7 times the lignin’, and 2 times the CaCl2. Relative fugitive dust emissions were also

highest on the untreated section. Based on cost to replace aggregate lost, traffic volume, cost of maintenance, and cost of suppressants they concluded that lignin’ and MgCl2 had

an identical cost per mile per year of $21 vehicle, while CaCl2 was at $26 and the

untreated was up to $36. They produced the following chart to highlight the cost analysis. (ADT is the average daily traffic).

(Sanders, et al. p. 396, 1997)

Based on these results, the group concluded that under high temperature and low relative humidity lignosulfonate appears to lessen the amount of dust produced. They also found that lignosulfonate and MgCl2 had the least total aggregate loss at 1.0 t/mi/yr/vehicle. The

study found a 28-42% reduction in annual maintenance cost for the treated sections compared to the untreated sections.

However, during a personal interview with this author on March 30, 2004, Dr. Sanders stated that he felt the MgCl2 was the superior product based on cost and

In a laboratory study, Epps and Ehsan (2002) compared aggregates from Wyoming, Texas, and Arizona to determine the effectiveness of water, CaCl2 and MgCl2 at

controlling dust. They used a crushed gravel stone from Wyoming in one segment of the study. This gravel contained approximately 9.9% fines, less than both the Texas and Arizona samples. They prepped the aggregates by allowing them to cure for 2 days at 32C and 35% relative humidity. They then sprayed the samples with water at a rate of 1.8 L/m2 to reduce the surface tension and increase the rate of penetration, and next applied magnesium chloride to one sample, calcium chloride to another, and water only to another sample. They found that applying chemical palliatives (MgCl2 and CaCl2) to

the Wyoming aggregate had a statistically significantly effect on reducing erosion caused by wind. This, they determined was related to the fact that the chemicals kept the surface wet even in windy conditions. The authors found no real difference between the MgCl2

and CaCl2, but noted that both lose their effectiveness over time.

Next they evaluated the effectiveness of the chemicals in a simulated traffic experiment. They found that a 38% solution of CaCl2 and a 30% solution of MgCl2 applied to the

Wyoming aggregate significantly reduced erosion caused by traffic compared to an aggregate sample that was only treated with water. They concluded that the application of CaCl2 or MgCl2 greatly enhanced dust control on unpaved roads in comparison to

water or no treatment and that there is not a significant difference between the two chemicals.

Gillies et al. (1999) from the Desert Research Institute at the University of Nevada and the San Joaquin Valley Unified Air Pollution Control District evaluated the effectiveness of four dust suppressants over a 14 month study. The suppressants that were tested included a biocatalyst stabilizer (EMC2_{), a polymer emulsion (Soil Sement), a petroleum}

emulsion with polymer (Choerex PM), and a nonhazardous crude-oil-containing material. The study identified an equation to calculate suppressant control efficiency, which they define as “the percent reduction in emissions between the treated and untreated sections:”

Efficiency= 1-(treated emission factor/untreated emission factor)

This study determined that estimating suppressant efficiency can be done using some simple methods in place of expensive monitoring. The authors determined that a

measurement of the bulk silt loading and the surface strength can provide an effective and inexpensive assessment of a suppressants effectiveness to reduce PM10 emissions. A suppressant treated surface that can achieve bulk silt content less that 20 g/m2 is

considered to be 90% effective at suppressing PM10 emissions. Further, if that surface can maintain flexibility (measured by a penetrometer) and can resist brittle failure then the suppressant is predicted to maintain effectiveness longer (Gillies, et al. 1999).

Effectiveness results The bio-catalyst (EMC2_{) was only 39% effective one week}

after the initial application and 0% effective after 11 months. The acrylic co-polymer was 95% effective after one week and approximately 85% after 11 months. The bitumen product was 95% effective after one week, 75% after 3 months, and 53% after 11 months.

The EPA has created an equation to determine the PM10 emission factor for unpaved

roads. This accuracy of this equation, however, is still under some question, particularly related to vehicle speed (Muleski/MRI 2002). Also this equation is designed around

average traffic weight, and does not account for heavier trucks (e.g. haul trucks).

E=2.6 (Silt/12)^0.8 (Weight/3)^0.4 / (Moisture/0.2)^0.3)

E = PM10 unpaved road dust emission factor for all vehicle classes

Silt = silt content, material less than 75 µm in the surface material Weight = average weight of the vehicle fleet (tons)

Moisture = surface moisture content (%) (EPA, AP-42, 1998)

The addition of moisture into the equation is fairly recent (Countess, 2001). It was added based on the recognition that climate and moisture play a large part in overall emissions from unpaved roads. An older version of this equation included variables for the number of wheels and speed, but re-analysis proved the variable not to be statistically significant (Countess, 2001). However, when using this model in an industrial setting it may be important to account for total wheels, traffic volume, and speed as variables. In addition, some feel that the type of aggregate should be included as it can often account for the long term amount of fines in the road surface.

Dust Suppressants

Road dust suppressants have evolved notably. Second and third generation products are now solving not only the dust problem but also cost efficiency, environmental, and labor issues (Engle, 2004). Positive results are now coming from even the toughest desert and drought environments where past products have failed (Engle, 2004). While EPA (AP-42, 1998) testing has shown that chemical dust suppressants can be effective (80% PM10

reduction when applied at regular intervals) there is not a single, cure-all solution. Some products work better in certain climates, various road surfaces, and under different traffic volumes, and each product comes with various advantages and limitations.

Dust suppressants are effective based on the fact that they agglomerate the fine particles in a road surface, binding the surface particles together, and increasing the density of the haul road surface material (Bolander & Yamada, 1999). If fines are lost as dust on an unpaved road it leads to the coarse material coming loose and can then be thrown or washed away. This can result in a road full of corrugations and potholes that require expensive maintenance (Sanders & Addo, 1993). “The main goal of a dust control is to stabilize the road surface; reducing the rate of aggregate loss and money spent annually in replacement,” (Sanders & Addo, 1993).

Dust control additives are beneficial not only at reducing dust emissions, but they also improve the compaction and stability of the road. According to Epps and Ehsan (2002) there are numerous factors related to the effectiveness of a dust palliative including application rate, method of application, moisture content of the surface material during application, palliative concentrations fines content, mineralogy of the aggregate, and environmental conditions.

Surface treatments to control dust emissions fall under two categories, wet suppression and chemical stabilization (EPA, AP-42, 1998). Wet suppression includes watering and the application of surfactants that keep the road surface wet. Chemical stabilization involves an attempt to change the physical characteristic of the road. Unlike watering, chemical suppressants require less reapplication and many act to form a hardened road surface (EPA, AP-42, 1998).

The addition of a wetting agent or larger sized particles reduces erodibility only at the interface of the surface and the impact vehicles (Thompson & Visser 2002). Dust control measures lose effectiveness on a scale ranging from immediately to weeks. The

palliative effects of water decays from 100% to 0% in a matter of hours while chemicals applied to control dust may decay over several days or weeks so it is important to understand the expected effectiveness of the product that you are working with (Thompson & Visser 2002).

A report issued by the U.S. Department of Transportation and the South Dakota Local Transportation Assistance Program states that in areas of high traffic volume, the cost of dust control can more than pay for itself. This is based on the fact that a good dust control agent can not only reduce material lost from the road, but also reduce the need for blade maintenance (Skoreth & Selim 2000). The same study determined that when a dust suppressant is not working well aggregate fines are lost, leaving only gravel size particles on the road, which leads to the formation of a washboard surface, reduced skid resistance, and potholes. The addition of agents (water or chemical) to reduce erodibility is based on the principle of increasing binding of the fines and gravel. (Thompson & Visser 2002). According to “Surface Mine Dust Control” by John Organiscak, et al. (2003), the best dust control plan should be dependent on the type of aggregate you have on your haul road. Selecting a dust suppressant, according to Sanders (1993) should depend not only on its performance characteristics, but also on the type of traffic and volume, roadway conditions, and the costs involved to achieve the desired level of control.

In the following selection and application guide, Bolander and Yamada (1999) suggest that selecting suppressants involves determining not only cost but cost effectiveness. They have devised the following list of benefiting factors that should be considered when selecting a dust palliative.

Palliative Factors

• Coherence of the Dust Particles (to themselves or larger particles) • Resistance to Traffic Wear

• Aggregate Retention

• Long-term Effectiveness

Water

Water assists in maintaining the compaction and strength of the road aggregate and reduces the potential loss of road material (Thompson & Visser 2002). Water is attractive because it is seen as a cost effective alternative, however the cost soon escalates with the addition of expensive equipment and operating costs. Data from the EPA’s Compilation of Air Pollution Emission Factors Volume 1,

Ch 13, AP-42 (1998) shown here in Figure 1.1 suggests that small increases in

moisture content (1 to 2 moisture level) initially results in large increases in control efficiency (from 0% to 75%) but beyond which additional efficiency grows slowly with increased watering (requires 2.5x more water to increase

effectiveness to 95%) significantly reducing cost effectiveness at the upper levels.

Figure 1.1 Dust Control Efficiency of Water

Similarly, a study by Rosbury and Zimmer (1983) found that watering once per hour has an efficiency of 40% in controlling dust, but when that rate is doubled the efficiency increases only by 15% to 55%.

Re-application is required at frequent intervals dependent on environmental conditions. Water retention in the Powder River Basin is generally poor due to high temperatures and wind speeds as well as low relative humidity. Increasing

water scarcity and cost adds to the scenario making water a temporary and typically un-economical solution.

Thompson and Visser (2002), based on the context of the arid South African coal mines, determined the degree of dust control achieved by watering is a function of the amount of water applied, time between applications, traffic volumes, weather conditions, wearing-course material, and the extent of water penetration into the wearing course. They determined that on an average degree of dustiness, a 50% reapplication is required at three hour intervals in the winter and every hour and a half in the summer. These intervals decrease with the addition of weight per vehicle, number of wheels, traffic volume, and climate conditions.

Thompson and Visser (2002) also found that traffic volume negatively correlated with total dustiness; which they explained based on observation, that higher traffic volumes led to more compaction of the wearing course and the removal of most loose material on the sides of the road as well as spillage from the vehicle. They also determined that vehicles lower to the ground with many wheels tend to cause an increase in dust based on the increase in wind shear.

Precipitation can greatly reduce dust emissions. Normally a rainfall resulting in at least 0.1 inch is assumed to suppress all emissions. However during a hot, dry summer’s day a rain of that same amount may only reduce emissions for hours as opposed to days (Countess, 2001).

Chlorides

Chlorides are salts that act as water attracters and absorbers; as hygroscopic compounds, they draw moisture out of the air to keep the road surface damp, although there is no physical binding (Skoreth & Selim 2000).

Chlorides are the most commonly used products for haul road dust control. A study by Rosbury and Zimmer (1983) showed that the highest control efficiency measured for a chemical dust suppressant (at that time), 82%, was for CaCl2 two weeks after application,

then decreased over time. The average during the initial two weeks was approximately 50%. After five weeks, the control efficiency declined to less than 20%.

The most common salts used to control dust are calcium chloride (CaCl2) and

magnesium chloride (MgCl2). When determining which is most effective, it’s

ability to produce a brine under adverse conditions such as high wind speeds, low humidity, or high traffic volumes is the best indicator (Sanders, 1993).

CaCl2

Calcium Chloride (CaCl2)has been used as a dust control and road

stabilizing agent for the last century (Epps & Ehsan, 2002). CaCl2 has

high affinity to water; increasing the tension of water molecules between soil particles. When applied the chemical increases the adhesive bond between particles resulting in retention of particles. According to Epps et al.(2002) CaCl2 has a wider range of effectiveness in regards to

temperature than magnesium chloride and loses its hygroscopic property at a temperature of 25C if the relative humidity drops below 32%. Calcium Chloride comes in three forms; flake at 77-80% purity, pellet 94-97% purity, and a clear liquid at 35-38% purity (Bolander & Yamada, 1999). Calcium Chloride is favored over Magnesium Chloride in areas or seasons of higher humidity, but it is not as effective in long dry spells (Bolander & Yamada, 1999). This chemical can significantly lower the freezing point of a water solution. In fact at 30% solution can have a freezing point of -60F (Larkin Laboratory, 1986). Because of this property several coal mines choose to use CaCl2 during the winter.

MgCl2

Magnesium chloride is a by-product of potash production and is only available in the liquid form (Ferguson et al., 1999). When determining if CaCl2 or MgCl2 is more effective there are contradictory findings and

statements. It seems the more recent studies are coming to the conclusion the MgCl2 is outperforming CaCl2,. According to Epps and Eshan (2002)

MgCl2 is more effective than CaCl2 in increasing the surface tension of

water molecules. Bolander and Yamada (1999) found that MgCl2 is

considered to be the best water absorbing product for drier climates because the chemical starts to absorb water from the air at 32% relative humidity regardless of the temperature. The product also increases the aggregate surface tension, creating a very hard road when the surface is dry, more so than CaCl2.

Both CaCl2 and MgCl2 are known to be corrosive to metals, because they attract

moisture to the surface and thus prolong the period of erosion (Bolander & Yamada, 1999). A positive attribute of both of these chemicals is that each allows a maintenance crew to re-grade and re-compact with little concern for surface moisture loss.

Gebhart et al.(1999) state that these salts provide the most satisfactory blend of application ease, cost, and dust control for semi-arid, semi-humid climates.

Organic/Non-Bituminous Chemicals

Compounds under this category include lignosulfonate, sulphite liquors, tall oil pitch, pine tar, and vegetable oils. These products generally perform well in arid environments but are not very effective when applied to aggregate surface material with few fines (Gebhart, et al., 1999). These dust control agents can be

very sticky and may harbor an unappealing odor. They often fail after heavy rains due to their water soluble, organic nature (Gebhart, et al., 1999). These products currently appear expensive, but the cost benefit equation continually changes. As a rule, they tend to be environmentally friendly. One compound with some supporting literature is lignosulfonate (lignin’).

Lignin’

Lignin’ or lignosulfonate is a by-product of the paper making process and is regarded to be generally safe environmentally because of the fact that it is an organic product. This product performs very well under arid

conditions. It binds particles together to increase the strength of the road and remains effective during long dry spells with low humidity (Bolander & Yamada, 1999). One of lignin’s weaknesses is that it is highly soluble in water, and its surface binding properties can be destroyed by heavy rain. It also has a tendency to stick to passing vehicles and is difficult to remove from painted surfaces (Frazer, 2003). Lignin is most effective and shows the greatest longevity when the road has been scarified and the product has been mixed into the aggregate (Sanders & Addo, 1997). However, it is this same scarification process that reduces the current use of lignin’ on some haul roads, as the perceived costs of the down-time due to

scarification and curing appears prohibitive.

A study using lignin’ on Pikes Peak’s unpaved roads conducted by Sanders and Addo (1998) revealed that the lignin was 2.7 more effective at suppressing dust than water. After spring snowmelt, 8 months after application, there were indications that the Lignin’ was still functioning in a good proportion of the test sections.

Petroleum Products

Petroleum products include asphalt emulsions (modified and not), dust oils/dust fluids, and petroleum resin emulsions. These products may be effective in a variety of climates; however, because they are by-products of petroleum and waste oils, they may contain toxic materials with significant environmental effects, and are not considered safe unless they have been processed to remove toxins (Gebhart, et al., 1999). These products are usually very expensive and like the organic products, are very sticky and have a foul smell.

Petroleum products are film forming and dust binding. They coat the dust particles and form a cohesive membrane that attaches each to adjacent particles. This results in a chained bond of large agglomerates that are too heavy to be dislodged by wind (James Informational Media, Inc., 2000).

Emulsified Asphalts

Emulsified Asphalts work to control dust, but their use is very limited and the product must be applied with specialized equipment (Skorseth and Selim 2000). The soil type and density of the road surface can greatly affect the rate at which a petroleum product penetrates the road. Roads that have been scarified to loosen the aggregate achieve the greatest amount of soil penetration. If the road has not been scarified the use of products with low viscosities will be ineffective (Bolander, Yamada 1999).

Polymers

Polymers such as polyvinyl acrylics and acetates work by binding the surface particles together to form a semi-rigid film on the surface. Polymers are

considered suitable for use under a wide range of climate and soil conditions and are most effective in environments that receive 8 to 40 inches of precipitation a year. Generally, a light compaction of the road after application of a polymer is recommended unless the product is mixed into the road surface (Bolander, Yamada 1999). Polymers are considered to be most effective on lightly trafficked

areas. These types of palliatives are usually non-toxic and environmentally

friendly (Gebhart, et al., 1999). Electro-Chemical Stabilizers

Electro-Chemical stabilizers include sulphonated petroleum, ionic stabilizers and bentonite. They are not likely to leach out and are stated to be very effective at reducing dust emissions in clay or sandy aggregate types. These products work well under a variety of climate conditions; however, many of these products have not been tested using standard laboratory tests under field conditions. Small scale trials should be performed to determine site specific efficiency prior to larger scale usage (Gebhart, et al., 1999).

Surfactants

Essentially surfactants are additives that make water wetter, reduce surface tension and allow better penetration of the palliative. At least one product (Haul Road Dust Control) claims a cumulative effect, whereby each new application boosts the effectiveness of the previous levels.

Several manufacturers of surfactants recommend prewetting of the roadbed, for their products to perform optimally. Similarly, Epps and Ehsan (2002) used prewetting in their laboratory study of aggregates and erosion.

There is a slight trend within mine operations in the Powder River Basin to use highly diluted applications of MgCl2 and CaCl2 in all water applications, instead of a surfactant.

There are environmental concerns associated with the use of certain surfactants. (refer to page 17 of this document for a discussion of these impacts)

Other Commercial Products

A list of commercial products is posted by The New Mexico Environment/ Department of Air Quality Bureau, which can be accessed on the web at

http://www.nmenv.state.nm.us/aqb/dust_control.html and in Table 3.1 of this report. There are some products listed here that are not included in this literature review. Classification of every product is not possible in part due to lack of a literature history and to the proprietary nature of the commercial formulas.

Mechanical Stabilization

Mechanical or road stabilization is the mixing of two or more substrate materials to create a road surface that has the correct fine gradient and plasticity. This method does not involve the application of chemicals although they can be used in addition to the

stabilization. One of the most effective substrate mixtures involves the addition of clays to a gravel and sand aggregate. The clay binds to the fine particles, and improves the roads stability and longevity. “When a gravel road resists lateral displacement during traffic, it is said to be mechanically stable, notes Gebhart, et al. (1999). This resistance is provided by the natural forces of cohesion and internal friction that exist in the soil.” Importance of Appropriate Dust Suppressant Application

Appropriate application of a selected product is key to the overall effectiveness of a dust control plan. “It can translate either into success or costly wastefulness, failure, and more difficult maintenance down the line,” according to David Engle (2004), author of “Road Maintenance Techniques and Products Have Made Great Strides.” Engle also

emphasizes timing as a critical component to successful application. He suggests an initial application during the narrow window between the spring rains and the start of the summer drought; “Keeping an eye on the weather forecast is critical; many expensive applications have been ruined by rainfall.”

Not only is the timing of the application crucial, but the manner in which the product is applied is just as important - if not more so. Sanders and Addo (1993) describe two ways in which suppressants are most typically applied; mixed-in-place and spray methods. The mixed in place method involves mixing the suppressants with the road aggregate. When this application procedure is used it not only suppresses dust but it also provides for an improved road surface resulting in reduced maintenance costs. Spraying involves the high pressure application of the material to the road surface. Topical spraying is effective for short periods of time, though, resulting in the need for reapplications throughout the season (Sanders & Addo, 1997). It is usually wise to try a test section to determine how well the product is going to work on a specific gravel, and what type of application works best (Skorseth & Selim, 2000).

Another key application principle was identified by Bolander and Yamada (1999). They suggest that adequate penetration of the dust suppressant into the surface material is imperative. This penetration should be 3/8 to 3/4 of an inch in depth. Proper penetration will reduce the loss of palliative from surface wear and allow the surface to resist

leaching. The process imparts cohesion, and resists aging.

Bolander and Yamada (1999) in the USFS Dust Palliative Selection and Application Guide, provide the following suggestions for applying dust suppressants:

Application Tips

• Repair unstable surface, grade (to a adequate depth) immediately prior to application

• Apply suppressants (especially salts) immediately after the wet season • Apply after a rain, or spray the road before application, to ensure

materials are more moist and thus more workable

• Adhere to manufactures recommendations on minimum application rate, compaction and curing time

• Use a pressure distributor to evenly distribute the suppressant • Water frequently and lightly, not infrequently and heavily

Scarifying

Sanders et al. (1997) include scarification of the road surface in their list of important techniques to be considered when applying dust suppressants and particularly specify the technique when using lignin. Organiscak et al. (2003) suggest that when using chlorides it is beneficial to loosen 1-2 inches of the road aggregate uniformly to allow the chemical to penetrate evenly. And like Bolander and Yamada (1999), the group stresses proper road preparation as a key to the effectiveness of a dust palliative, especially creating a good crown and drainage when using a chloride. They also state that when using a chloride the roadway should not be compacted before applying the chemicals and the road should be kept at optimum moisture before application, this allows the product to be absorbed quickly and evenly.

For some suppressants it is recommended to keep traffic off the road surface for two to three hours after application to allow the product to absorb and cure (Skorseth & Selim, 2000). This characteristic is expected to be considered a limitation by mine engineers, who would have difficulty justifying the necessary down time involved on mine haul roads (see survey results, Appendix A). Grading after application also partially destroys the effect of many dust suppressants (Ferguson et al., 1999). Because of this, grading should be postponed after heavy application of suppressant for as long as possible. The EPA has recommended that a diluted reapplication be applied periodically (2 weeks to a month) to control loose surface material. They also state that weather related

application schedules should be considered prior to implementing a dust control program (EPA Fugitive Dust, 1992).

The type of road aggregate is one factor that determines the type of dust control that is most effective. Organiscak et al. (2003) recommend effective applications for various road types in their article “Surface Mine Dust Control.” In road surfaces with poor size gradation, water is the only effective solution because chemical suppressants (most of which are water soluble) cannot compact the surface or form a new surface because they will leach. In sand they recommend bitumens because of the fact that they are not water soluble. On a road with good gradation all chemical suppressants can be used, and on a road with too much silt the road should just be rebuilt, as no dust control will be effective (Organiscak, et al., 2003). If a haul road is left untreated by a dust suppressant aggregate replacement will become necessary over shorter periods of time and maintenance will be required more frequently (Epps & Ehsan, 2002).

Education and Training

In addition to using prescribed application procedures, John Watson and Judith Chow (2000) from the Desert Research Institute suggest that the success of a dust control problem depends on outreach and education programs for contractors and public works agencies. In a coal mine, education should be extended to

maintenance personnel. Environmental Impacts

The major environmental concern when using dust suppressants is contamination of ground and surface water. Thomas Piechota, an assistant engineering professor at University of Nevada Las Vegas was quoted in Lance Frazer’s “Down with Road Dust

(Innovations)” as saying it doesn’t matter what suppressant is used, there will always be

some level of water quality impact (Frazer, 2003). Peichota noted that petroleum

compounds were more harmful than suppressants such as magnesium chloride. Another area of impact he mentioned is the fact that the suppressants are creating a somewhat impenetrable road surface, which will increase runoff, which has its own hydrologic impacts.

There is some potential for off-site plant damage during periods of heavy rainfall

(Ferguson et al., 1999). All necessary precautions should be followed to unsure that these chemicals are kept away from water sources.

The following photo taken in June of 2004 in Larimer County, Colorado between Lyons and Estes Park strongly suggests runoff from a highway treated with a 30% solution of Sodium Chloride (rock salt) and sand may be impacting ponderosa and other pines (Anon’ CoDOT, 2004).

While no Wyoming coal mines use Sodium Chloride to treat dust on haul roads that we know of, the expected negative publicity from this environmental impact (near Boulder) may carryover into other road salts such as MgCl2 and CaCl2 which are heavily used.

There is no scientific evidence yet of the actual cause of the tree damage, but the die-off appears to be confined to an area within 50’of the roadway for 20 plus miles, strongly suggesting road runoff and/or exhaust fumes as contributing factors. Conversely, few Wyoming coal mine haul roads traverse timbered acreage, limiting this specific impact. Surfactants, on the other hand, may pose some environmental concerns. M. Warhurst (1995) in a report to Friends of the Earth, England, outlines toxicity concerns with alkylphenol ethoxylate (APEO) surfactants, and calls for a more widespread ban on their use (The surfactant is currently banned in several European countries). He recommends the replacement of APEOs with linear alcohol ethoxylate surfactants, which are readily biodegradable according to Consultants in Environmental Sciences Ltd (CES, 1993).

Works Cited

Anonymous Colorado Department of Transportation Official. Personal Interview with Author. June, 2004. Boulder, CO.

Bolander, P., Yamada, A. (November 1999). “Dust Palliative Selection and Application Guide.” United Department of Agriculture, Forest Service, Technology and Development Program. San Dimas Technology and Development Center, San Dimas, California. Countess, R. et al. 2001. Methodology for Estimating Fugitive Windblown and

Mechanically Resuspended Road Dust Emissions Applicable for Regional Air Quality Modeling. Paper in International Emission Inventory Conference, "One Atmosphere, One Inventory, Many Challenges." Denver, CO, April 30. (Power point presentation slides) Engle, D. (2004). “Bidding Farwell to Dusty Roads, Road Maintenance Techniques and Products Have Made Great Strides,” Forester Communications, Erosion Control

January/February 2004. www.forester.net

Environment Australia, Department of the Environment and Heritage (1998). “Dust Control Best Practice Environment Management in Mining.” Sustainable

Industry/Sustainable Minerals.

Environmental Protection Agency 450/2-92-005 (1992). “Fugitive Dust Background Document and Technical Information Document for Best Available Control Measures.” Office of Air Quality, Planning and Standards, Research Triangle Park, NC.

Environmental Protection Agency (1998). “Compilation of Air Pollution Emission Factors, AP-42. ” Volume 1, Ch 13, Unpaved Roads. Office of Air Quality, Planning and Standards, Research Triangle Park, NC 27711.

Epps, Amy, Ehsan, M. (2002). “Laboratory Study of Dust Palliative Effectiveness.” Journal of Materials in Civil Engineering. September/October 2002 p.427-435. Frazer, Lance (2003). “Down with Road Dust (Innovations),” National Institute of

Environmental Health Sciences. Env Health Perspectives Dec. 2003 V111 i16 pA892(A). Ferguson, J.H. et al. (1999). “Fugitive Dust: Nonpoint Sources.” Agricultural MU Guide. University of Missouri-Columbia. Agricultural Publication G1885.

Gebhart, D.L., Denight, M.L., Grau, R.H., (1999). “Dust Control and Technology Selection Key.” U.S. Army Construction Engineering Research Laboratory, Land Management Laboratory, Resource Mitigation and Protection Division; and the U.S. Army Engineer Waterways Experiment Station, Pavements Division.

James Informational Media, Inc (2000).“Better Roads, a Look at Dust Control and Road Stabilizers.” Better Roads Magazine www.betterroads.com/articles/prod500.htm

Larkin Laboratory (1986). “Calcium Chloride and Magnesium Chloride for Dust Control.” 1691 N. Swede Rd. Midland Michigan 48640

N. Carolina Department of Environment and Natural Resources Division of Air Quality (2003). “Economic Analysis of Particulates from Fugitive Dust Emissions Sources.” Organiscak, J.A., et al. (2003). “Chapter 5. Surface Mine Dust Control.” In Handbook for Dust Control in Mining, Center for Disease Control, IC # 9465.

Rosbury, K.D., Zimmer, R.A. (1983). “Cost-Effectiveness of Dust Controls Used on Unpaved Haul Roads, Volume 1: Results, Analysis, and Conclusions.” PEDCo Environmental, Inc. U.S. Bureau of Mines.

Sanders, T. (2004). Personal Interview conducted by Temple Stevenson on the campus of Colorado State University, March 30, 2004.

Sanders, T.G., Addo, J.Q. (2000). “Experimental Road Dust Measurement Device.” Journal of Transportation Engineering, November/December 2000.

Sanders, T.G., Addo, J.Q. (1998). Pikes Peak Road Dust Project. Colorado State University.

Sanders, T., Addo, J.Q., Ariniello, A., Heiden, W.F. (1997). “Relative Effectiveness of Road Dust Suppressants.” Journal of Transportation Engineering September/October 1997. p 393-397.

Sanders, T.G., Addo, J.Q. (1997). “Effectiveness and Environmental Impact of Road Dust Suppressants.” MC Report NO. 94-28, Mountain Plains Consortium.

Skorseth, K., Selim, A.A (2000). Gravel Road Maintenance and Design Manual. South Dakota Local Transportation Assistance Program. U.S. Department of Transportation, Federal Highway Administration.

Thompson R.J., Visser, A.T. (2002). “Benchmarking Management of Fugitive Dust Emissions From Surface-Mine Haul Roads.” Transaction of the Institute of Mining and Metallurgy, 111/April, pp A28-A35.

Watson, J.G., Chow, J.C. (2000). “Reconciling Urban Fugitive Dust Emissions Inventory and Ambient Source Contribution Estimates: Summary of Current Knowledge and Needed Research.” Desert Research Institute, Energy and Environmental Engineering Center. DRI Document No. 6110.4F

Wyoming’s Long Term Strategy for Visibility Protection- Review Report. 2003. Prepared by the Wyoming Department of Environmental Quality, Air Quality Division

II. Recommended Practices and Best Available Control Measures

Best practices for dust control in a Wyoming surface coal mine simply means utilizing the most practical and effective methodology that is currently available. In many cases best practices can be achieved by appropriate planning and or the identification and control of dust sources as they are identified.

According to “Dust Control Best Practices Environmental Management in Mining” prepared by Australia’s Department of the Environment and Heritage, best practices for dust control in a surface mine operation should include:

Planning

The identification of potential sources of dust A prediction of dust levels likely to occur An evaluation of the effect of the dust

The incorporation of the dust predictions and control measures into mine planning and design

Observation

Observations of point sources which can be readily identified Dust emission rates based on qualitative estimates and models Controlling

An aware workforce

Integration of dust control into operations planning (construction, topsoil stripping, blasting)

Intergrading dust control provisions into work practices (use of chemical palliatives)

Monitoring and feedback dust emissions

Efforts based on observational and qualitative assessments

Awareness of current methods and technology used for dust control

(Environment Australia, 1998, p.8-9)

The most effective, consistent and cost effective dust suppression strategy is a long term plan that looks to control dust before the problem arises. Applying dust controls after the problem arises is impractical and costly. Because of this, mine planning has a very significant role to play in dust control (Environment Australia, 1998).

Dust Control Strategies

When developing a dust suppression plan there should be a set of standardized

procedures for application and maintenance. Standardized application this will minimize confusion on how the product is applied and maximize the product’s effectiveness. A sound set of road application and maintenance procedures will result in safer working conditions, a decrease in actual maintenance work, in addition to a decrease in overall road dust emissions.

The following quote prepared for the U.S. Army Construction Engineering Research Laboratories, highlights the fact that controlling road dust emissions should be seen as a process, not just the application of chemical palliatives.

“The best way to avoid dust problems is to ensure that roads are properly maintained by surface grading and shaping for cross-sectional crowning to prevent excessive road surface wearing and consequent dust generation. Chemical dust suppressants are considered a secondary solution, to be used only when maintenance practices have been implemented to the greatest extent possible,” (Gebhart, et al. 1999, p. 10)

Gebhart, et al. (1999) recognize three major types of dust control methods including: (1) Construction and Maintenance; (2) Mechanical Stabilization; and (3) Chemical

Palliatives.

Construction and Maintenance

Good construction and maintenance practices are fundamental to providing durable and erosion resistant trafficked surfaces in dust-prone areas. Due to environmental and traffic deterioration of the aggregate surface haul roads require frequent maintenance. Gebhart, et al. (1999) suggest that the following construction and maintenance steps be performed to prevent dust emissions on unpaved roads:

Use of a well graded aggregates consisting of an adequate amount of fines that can be used as cohesive binders.

Retention of a crown on the road surface to provide adequate drainage. Drainage for the wearing surface, shoulder, and verge.

Proper compaction of the wearing surface after the addition of aggregate and grading.

Reduced maintenance grading during dry weather conditions.

Creating adequate surface drainage should be provided in order to minimize damage caused by moisture. Standing water in the roadway will lead to surface softening and failure (Skorseth, Selim 2000).

Compaction of the road after adding aggregate and grading will increase the density and strength of the wearing surface as well as retention of larger aggregates (Gebhart, Denight, Grau, 1999).

Mechanical stabilization

A road is considered stable when it resists lateral displacement caused by traffic. Mechanical stabilization is achieved by mixing soils of two or more gradations. This type of resistance is attributed to the natural forces of cohesion and the internal friction that are present in the soil (Gebhart, et al. 1999). Dust control products often have an added benefit of increasing soil stabilization. According to Skorseth and Selim (2000) in “Gravel Road Maintenance and Design Manual,” soil stabilization will control the loss of fines from the road surface that typically result in distresses such as wash-boarding and reduced skid resistance. This type of unstable road becomes hard to maintain and hauling in new road aggregate with a higher percentage of fines becomes expensive. Aggregate loss can be as much as one ton of aggregate per mile per year on a typical unpaved county road for each vehicle that passes over a road daily (Sanders, Addo, 1998) and losses would be substantially higher on haul roads. A reduction in blade maintenance is another benefit of using a dust control product. When the road remains tightly bound and stable it will require less maintenance (Skorseth, Selim 2000). Manufactures recommend a delay in blading for as long as possible once a product has been applied because blading can reduce or remove the dust control product from the road.

Chemical Palliatives

The use of chemical palliatives should be used in conjunction with the two other methods, especially if mechanical stabilization is cost-prohibitive and high dust

emissions persist. When chemical dust palliatives are maintained over a long-term basis there can be a 50-75% or more reduction in dust generation. Gebhart, et al. (1999) feel that the dust control methods should be applied in the order discussed here: (1)

construction and maintenance, (2) mechanical stabilization, and (3) chemical palliatives in order to reduce dust emissions successfully.

Applying Chemical Palliatives

Before applying any dust suppressant, at minimum basic road maintenance needs to be performed. Preparing a road before the application of chemical palliatives should include the construction of a good crown on the driving surface, good shoulder drainage, and a fresh blading of the road surface to remove any potholes or other imperfections (Skorseth, Selim 2000). In addition scarifying the road in order to loosen the soil a minimum of one to two inches can be done. This will leave a uniform depth of loose aggregate across the road will allow even and fast penetration of the dust control product into the road surface. Several authors and product distributors have cited the need for scarification because of the added depth of saturation it can provide. This deeper saturation is directly related to increased dust control effectiveness. Although there may be some added costs and

time associated with scarification, in the long run it is generally believed the extended life and increased effectiveness of the product outweighs the initial application preparation costs. The following list is a compilation of

recommendations by Bolander and Yamada (1999) for applying dust control products from numerous authors and product distributors.

Suppressant Application Tips

• Repair unstable surface, grade (to a adequate depth) immediately prior to application

• Scarify the road to loosen the surface material to allow for even penetration of the product into the soil

• Apply suppressants (especially salts) immediately after the wet season (apply directly after a rain or pre-wet the surface prior to application) • Adhere to manufacturer’s recommendations on minimum application

rate, compaction and curing time

• Use a pressure distributor and realign the water nozzles on the application truck to ensure a even distribution of the suppressant • Water frequently and lightly, not infrequently and heavily Water as a Palliative and its application

Applying water on problem areas provides immediate but short term results. This inexpensive method of dust control is recommended as a short-term solution to dust emission problems (Gebhart, et al.,1999). Water is effective at controlling dust emissions because the water surrounds and adheres to the dust particle making it difficult for the dust particles to move. However, under continual wetting conditions a pumping of the fine to the roads wearing surface may occur (Gebhart, et al.,1999). Excessive moisture on unpaved roads can lead to negative effects

including a reduction in the strength of the road bed, road deformation under vehicle loading, and an increased potential for brittle failure which produces smaller particles that can then be crushed by vehicle tires (Rosbury and Zimmer, 1983). In the EPA’s Compilation of Air Pollution

Emission Factors Volume 1, Ch 13, AP-42 (1998) it is noted that small

increases in moisture content result in large increases in control efficiency, but only up to a point, beyond which additional efficiency grows slowly with increased watering.

Water droplet size has been shown to be an important factor in dust suppression effectiveness (Gambatese, James 2001). If water droplets are too large, smaller dust particles generally just slipstream around the droplets without actually making contact. If the droplets are too small they just mix and circulate with the dust particles without actually wetting them. Small droplets may be negatively affected by wind and surface tension. An optimal water droplet size for surface impaction of fine

particulate agglomeration is approximately 500 um. To create an effective water spray system hollow cone nozzles which produce the greatest control of dust while minimizing clogging should be used. Angling the nozzles on the truck body in a horizontal angle or lower will protect the droplets from wind.

Application practices issues

There can be other problems that inhibit the effectiveness of using a dust control palliative. These include a lack of communication between water truck operators,

applying a product where not needed (such as shoulders and berms), and confusion as to the desired outcome of using the product. The information in the following chart is taken from a presentation prepared by Rose Haroian, Environmental Manager for the Powder River Coal Company; and is helpful in addressing some of the operational problems that are encountered when using a dust palliative and or water to suppress dust.

Table 2.1 Dust Control Operations Recommendations

Problem Solution

Water trucks aren’t synchronized Communicate between water trucks to determine where watering has and hasn’t taken place Operators are seeking dust elimination rather than

dust control Maintain an understanding of what the desired goal of watering is, and have indicators that determine when the roads need watered. Sometimes the visual indicators are not accurate.

Roads treated with dust control products are being

watered too much Newly treated roads only need water when they become visibly dusty. Coal Dust caused by spillage Do not attempt to apply water to coal spills, clean up

the spillage instead

Over watering creates more dust Communication needs to occur between the blade and water truck operators, don’t water where it is not needed

Spraying water in high wind Adjust speed and location on the road to account for wind.

Soft Spots Don’t over water, spot watering in the same location

will cause road problems

Sprayers are not properly positioned Modify sprayer locations to ensure the angles are optimizing the desired spray area

Watering inappropriate areas such as berms Watch where you are watering. Relocate if needed. If this does not work turn off the outside sprayer. Blades blade off watered areas Blades should only blade where it is necessary Blades blade rock and chemicals into ditches Carry windrows across the road. Do not leave

Real Time Data - Monitoring

Visual indicators to perceive dust emissions problems are a useful technique, however it is hard to keep an eye on dust emissions 24 hours a day. The collection of real-time dust emission data from air quality monitors is important. A reliable PM10 emission inventory is required for the state’s SIP and is logical so that

source specific dust control measures can be taken. The dust may be coming from an overburden pile or a county or coal bed methane (CBM) road, so automatic watering of the haul road would be inappropriate. The use of real-time data incorporated with the notification of personnel and a record of where the dust is coming from as well as weather conditions can create can create a higher understanding and accountability of dust emission exceedences.

The monitoring network for particulate emissions in the Powder River Basin is extensive; operating since 1989, according to Wyoming’s Long Term Strategy for Visibility Protection: 2003 Review Report (Wyo DEQ, 2003). Additional

monitoring, including that of meteorological data is conducted at IMPROVE (Interagency Monitoring of Protected Visual Environments) locations.

Figure 2.1 illustrates a sample protocol used by one mine to be followed based on various types of exceedences and events (aided by real-time data).

Figure 2.1 Sample Air Event Outline:

Air Event Logging and Action Levels (_____________Mine, WY)

If ug/m level = 300 (over 1 hr)

(1) notify production supervisor Supervisor’s actions include:

ensure adequate water trucks operating record water usage for this shift

ensure problem areas are addressed notify____________________ If ug/m level = 80 (24 hr rolling average)

(1) notify production supervisor Supervisor’s actions include:

Same as above, plus:

Estimate wind speed and direction

Consider modifying plant operations contributing to dust

Inspect dust generating segments of operation to ensure proper dust control Document conditions including offsite impacts, meteorological conditions

Document actions taken

Take photographs to document primary sources of dust (on or off site)

Notify Senior Environmental Engineer if cause of dust event cannot be identified If ug/m level = 100 (24 hr)

(1) Notify Operations Manager(OM), who will notify Sr. environmental engineer (SEE)and production coordinator(PC). (2) Notify General Manager (GM) if curtailment of operations is expected If ug/m level=150 (excursion event)

(1) Notify the ____ Environmental Manager as well as OM, SEE, and PC, and GM. (2) Contact the Wyoming Dept of Environmental Quality by phone

Actions to consider

Curtail production operations

Contact neighbors contributing to dust impact (county roads, landowners Water/suppress dust on any identified problem areas

Document actions taken

If ug/m level=120 (24 hr)

(1) Notify same as above (150 level) Contact ____ Environmental Manager

Properly applying and maintaining a dust control product can be more important than selecting the perfect one because the manner in which a product is used directly relates to how effective the product will be. Cost-effective dust control depends not only on

application but also on proper maintenance and regular reapplication. Properly using a dust control product can reduce the amount of grading that is required, decrease the amount of road aggregate that is lost, and reduce vehicle wear and tear. Ultimately all of these benefits result in a savings of time and money, which is illustrated in Table 3.2 of this manual.

A BACM recommendation from Dona An~_{a County, New Mexico (2000) can be}

summarized as Smart Timing and involves the timing of either operations or palliative application so as to prevent the most likely exceedences due to meteorological

conditions.

The Arizona Department of Environmental Quality (ADEQ, 2001) notes that

technological and economic feasibility is a valid criteria for determining BACM and adds that BACM will change as new products and approaches are proven technologically and economically feasible.

Gaffney and Shimp (1997), in a report for the California Air Resources Board, call for improved GIS technology to calculate and spatially analyze emissions.

In compiling BACM recommendations, the author visited with mine engineers. To ascertain the opinions of surface coal mine engineers in the Powder River Basin relative to dust suppression on haul roads a survey was developed and distributed. Five responses were recorded and are summarized in Appendix A. of this report.

Best Available Control Measures (BACM) Recommendations

The following control measure recommendations have surfaced from a thorough review of the literature and analysis of the fugitive dust situation facing Wyoming surface coal mines. Mine representatives, agents from the Wyoming Dept of Environmental Quality, and Region 8 of the EPA, and other appropriate parties should review and discuss the strategies for technological and economic feasibility and expected effectiveness before a final BACM list is completed.

Table 2.2 Best Available Control Measures - BACM (Recommendations) For Controlling Fugitive Dust on Mine Haul Roads

Keywords Recommended Practice Monitoring

Reporting Develop a protocol (similar to example given in Figure 2.1) for notification of appropriate plant personnel and environmental agencies (e.g. Wyoming Department of Environmental Quality) in reaction to various dust events.

Monitoring

Reporting Develop a report template for documenting and reporting dust events

Controlling Be prepared to supplement current water truck fleet with rental/vendor trucks to ensure no exceedences occur

Inventory

Monitoring Use real time g/h TEOM samplers to make adjustments in mine operations as necessary Controlling,

Documenting Develop a chemical suppressant regimen that effectively and consistently controls dust. Be prepared to justify this regimen by monitored and documented use to determine effectiveness at varying climatic conditions. Become aware of emerging technologies.

Documenting

controlling Closely document water usage along with climatic conditions (current effectiveness of water is hard to determine due to lack of reliable data)

Communication Share successes and failures with other mine engineers, as dust is a regional issue, not a site issue.

training,

communication Periodically conduct personnel appropriate training in dust monitoring and suppression. Ensure communication across all levels of operation.

Monitoring Maintain at least one person on site who is certified in opacity monitoring or contract with a vendor certified in opacity monitoring

Modeling Seek to prevent dust rather than react to it. Include weather forecasting into dust event predictions Incorporate GIS modeling into dust control planning.

Controlling Maintain equipment in optimal condition (e.g. spray nozzles)

Controlling Follow proven or recommended palliative application procedures (e.g. surface prep, application rates and times, curing, compaction and grading)

Controlling Take action to reduce spillage from haul trucks, as coal and overburden spillage destabilizes the road and significantly reduces the effect of palliatives. Maintain optimal roadbed conditions.