Chapter 4. Data Analysis

Dust Quantification

The dust monitoring was carried out from the Spring through the Fall of 1993, the time in which dust generation in the Larimer County is severe. The construction of the test sections was done on the10th of May, but it wasn't until 40 days later before the dust measurements started. The treated sections were dust free in those early days after the treatment. The development, calibration and field testing of the dust measuring device also took place at the time. Dust measurement was done once a week although there were times when the weather conditions in the field did not permit measurements to take place exactly at one week intervals.

To demonstrate the precision in the dust measurements made using the Colorado State University Dustometer, nine replicate samples were done on the untreated test section at a speed of 45 MPH. Table 3 shows the data and its distribution. A mean of 2.74 grams was obtained with a standard deviation of 0.21 and a variance of 0.04.

It is obvious from field observations that the speed of a vehicle is a very important factor in dust generation from unpaved roads. To help qualify this phenomenon, dust measurements were made at various speeds; 20 MPH through 50 MPH on the untreated test section. For the mile long run the dust amounts at 20, 30, 40 and 50 MPH are shown in Figure 9. Adjusting the dust amounts for a three minute run takes into account the fact that the device setup involves the suction of a dust cloud over the filter, the data in Figure 10 was generated. Surprisingly Figure 10 show a linear relationship between the speed and amount of dust generated. The coefficient of linear regression r² for this plot is 0.98. Including more data points during the measurement did not change the linear relationship as shown in Figure 11. Table 4 shows the dust amounts measured on all the five test sections. In all, fourteen measurements were made during the research period. All data points are averages of three replicate samples.

Speed: 45 mi/hr
Length of run: 1 mile
Untreated Section

Mean = 2.74g +/- 5.8%
Standard deviation = 0.21
Variance = 0.04

Runoff Analysis

All runoff samples collected from the various rainfall events were analyzed by measuring total dissolved solids (TDS), conductivity, total hardness and the amount of free chloride present in the samples. The procedure used in the analysis were according to the Standard Methods for the Examination of Water and Wastewater, 16th Edition, 1985. Table 5 shows the total hardness measured in all the runoff samples collected from both the road and non-road surfaces. The data analyses is still ongoing and in the final report all the detail analysis will be presented.

Figure 9. Amount of Dust vs. Speed

Figure 10. Amount of Dust as a Function of Speed

Figure 11. Amount of Dust vs. Speed

Dust weight = average of 3 measurements
Passes are run in the same driving lane
Length of each treated test section = 1.00 miles
Length of untreated section = 1.0 mile
Treated Sections done on 05-10-93
Speed = 45mi/hr