Evaluation of Envi-Rox 2000

Results of the CENE 330 Emission Inventory Project

Prepared for:
CENE 330 Terry E. Baxter, Ph.D., P.E.
Air Quality Engineering Bldg. 69, S. McConnell Dr.
Fall 2003 Course File PO Box 1560
June 9, 2004 College of Engineering and Technology

Prepared by:
Northern Arizona University
Flagstaff, AZ 86011-1560


Envi-Rox 2000 is a surface-applied dust suppressant produced from ponderosa pine resin used to control fugitive dust from unpaved roadways. While the effectiveness of Envi-Rox 2000 has been reported to be quite good, no studies have been conducted to directly evaluate its effectiveness. TheCENE 330 Air Quality Engineering course at Northern Arizona University, frequently seeks opportunities to integrate field-oriented emissions inventory project activities as a way to gain practical experience with air quality issues. During the Fall 2003 semester, this course was able to integrate an evaluation of Envi-Rox 2000 for this purpose.

The overall purpose of performing this study was to provide students with an understanding of and the actual experience of conducting a particulate matter (PM) emissions inventory for both paved and unpaved roads. The evaluation of Envi-Rox 2000 was specifically conducted as part of this overall study for the purpose of determining PM emission estimates before and after application to a section of unpaved road. This report present only the data and results of the emission inventory project that relates directly to the ability to evaluate Envi-Rox 2000 effectiveness as a dust suppressant.


Each fall semester the CENE 330 Air Quality Engineering class conducts emissions inventory projects as a means to provide students with hands-on experience of conducting an emissions inventory. This project-based learning approach has been successful in providing students with a much better understanding and reinforcement of what an emission inventory involves than what would otherwise be possible through a traditional series of lectures.

During the fall 2003 semester, the CENE 330 class was presented with a project that would conduct a PM emissions inventory for the paved and unpaved roads at Fort Tuthill County Park in Coconino County, Arizona. Also, during the course of this semester, Lyman Dust Control was scheduled to apply Envi-Rox 2000 to approximately a one-third mile section of unpaved road and an evaluation of dust suppressant effectiveness was incorporated as part of the overall emissions inventory project.

The section of unpaved road was scheduled to receive an application of Envi-Rox 2000 is located along the west and north sides of the park’s grandstand and racetrack facility. Sampling of the loose material along this section of road was conducted at two separate locations, as shown in Figure 1. Samples were collected at each location and analyzed before and after the dust suppressant was applied to the road’s surface.


Figure 1. Unpaved road application of dust suppressant and sampling locations. 

The field sampling and laboratory analysis methods in AP-42 for determining unpaved road PM emission factors (US EPA, Compilation of Air Pollutant Emission Factors, Volume I: Stationary Point and Area Sources, Chapter 13 Miscellaneous Sources, Section 13.2.2, Unpaved Roads) were used during this study to evaluate the effectiveness of the Envi-Rox 2000 dust suppressant.

Road Conditions and Application

The unpaved roads on Fort Tuthill County Park’s grounds are typically primitive and covered with a
relative fine material, up to an average depth of about 0.25 inch. The general condition of road
conditions prior to the application of dust suppressant is shown in Figure 2. Figure 3 illustrates the amount of loose surface material typically present. Here, a section of the loose material has been removed to expose the hard-packed soil beneath. Traffic traveling along these roads can generate significant amounts of fugitive dust, particularly when special events such as the county fair or rodeos are held. Figure 4 shows the amount of dust that can be generated by a single truck traveling at approximately 15 miles per hours.


Figure 2. Unpaved road prior to the application of dust suppressant. 


Figure 3. Loose material typically found on road surface before application. 


Figure 4. Fugitive dust emitted by vehicular traffic. 

On October 1, 2004, approximately 2,400 gallons of Envi-Rox 200 dust suppressant was applied to 4,800 square yards of the road’s surface using a Bearcat computerized spreader truck. Weather conditions were excellent during the application with an initial temperature of 63°F and warming, low relative humidity (< 20%), only partial cloudiness, and no precipitation was forecasted for the immediate future. Figures 5 and 6 show the spreader truck in the process of applying product to the entire width of the road’s surface and the uniform distribution of the product that was achieved.

The Envi-Rox 2000 product applied, was readily accepted by the surface material and nearly absorbed within 10 minutes of application. Figure 7, shows the appearance of the free product on the road’s surface within 1 minute of its application. After 10 minutes the road surface appeared as shown in Figure 8. The small surface holes or pits that are visible in Figure 8 after 10 minutes were caused by air bubbles that formed and emerged at he surface as the product penetrated into the voids within the surface material, displacing the air.


Figure 5. Envi-Rox 2000 being applied to road surface by a Bearcat spreader truck 


Figure 6. Uniform distribution during application was accomplished across the entire width of the road. 


Figure 7. Road surface appearance after 1 minute from application. 


Figure 8. Appearance of road after 10 minutes from application. 

After about 30 minutes from its application, the dust suppressant appeared to have fully penetrated into the surface material, fines were bound together, and surface drying and hardening had occurred to the extent that the road surface could accept modest vehicular traffic without damage. Figure 9 shows the appearance of the road surface after 30 minutes and its visible discoloration when compared to the adjacent section of road that did not receive dust suppressant.

After 21 days from application, the weather remained seasonably warm and dry throughout, and the road surface remained hardened and discolored. Even though small loose rocks were now present as can be seen in Figure 10, there was minimal loose fine material. Also on day 21, a small hole was dug into the hardened road surface to check penetration depth. In Figure 11 it can be seen that at this particular location, the entire depth of previously loose surface material, approximate 0.2 inches, had been sufficiently saturated with the Envi-Rox 2000 product that it was hard throughout.


Figure 9. Appearance of road surface with and without dust suppressant applied after approximately 30 minutes. 


Figure 10. Road surface 21 days after application showing the hardened surface with minimal loose material. 


Figure 11. Test hole dug 21 days after application showing the penetration depth of dust suppressant and the hardened surface material. 


Samples of loose surface material were collected during the week prior to application and again from one to two weeks after application. Two samples were collected from each location prior to the application of dust suppressant and one sample was collected at each location afterward. Once collected, these samples were transported to the laboratory. Each sample was analyzed for soil moisture content and then sieved to determine the silt fraction or percent fines less than the 200-mesh screen. The results of these analyses are shown in Table 1 below.

Soil moisture and silt analysis results for unpaved road surface material before and after application of Envi-Rox

  Sample Location   Moisture Content (%)   Silt Fraction (% < 200 mesh)   Moisture Content (%)   Silt Fraction (% < 200 mesh)
  A1   0.67   15.5   0.43   8.2
  A2   0.67   14.9
  B1   0.45   14.5   0.37   9.0
  B2   0.45   17.9