Waste Dump Design for Erosion Control

Authors
Ray Chopiuk
S.E. Thornton
Resource Date:
1987
Page Length
45

The Waste Dump Design for Erosion Control study was initiated in 1983. Several foothills/mountain coal mine waste dumps were selected for the purpose of evaluating the effects of final configuration on the amount of surface erosion occurring on those dump surfaces. A series of research plots was established on the reclaimed slopes, and a program to monitor the amount of material movement on the slopes was begun. The objectives of the program were: 1. To determine the influence of the length and steepness of reclaimed waste dump slopes on erosion; 2. To determine the effect of time and vegetation cover on erosion (i.e., does the age of the material, since reclamation, affect the amount of material movement on the slopes); and 3. To develop, if possible, a model that will predict the effects of those factors contributing to erosion that are within the control of the mine operator, namely slope configuration and nature of material used to cover the slopes. Data on the movement of the slope surfaces were collected twice in 1983, three times in 1984, and three times in 1985. The total amount of elapsed time between the final measurements obtained in 1985 and the time monitoring began in 1983 was 24 to 26 months. This report presents a history and outline of the project as well as a discussion of the results of the monitoring program. The analyses which were performed on the data include checks on the frequency distribution, plot means and standard deviations, analysis of variance, tests for paired variables, rejection of outliers, and regression. The data were compiled in tables and graphs and placed in Appendices A through K under separate cover. Due to the large volume of material in these Appendices, they have not been reproduced in this report. Readers should contact the author for information regarding availability of the data in the Appendices. In general, the most reliable and dramatic results were obtained from the one slope which was monitored as soon as reclamation was completed. Over the two year time period that erosion was measured, the total amount of erosion on most other slopes was minimal which made it difficult to establish models or trends of the influence of contributing factors on erosion itself. A general observation of all the results, based on two annual periods of erosion measurement on the slopes, is that there appears to be no need for a great deal of concern about waste dump erosion, Other than for a small initial amount of surface deflation immediately after re-grading is complete, no significant amount of material seems to leave the slopes. From knowledge of the nature of the materials involved (i.e., extremely coarse-grained “topsoil” overlying blocky, angular waste rock one concludes that even measurable erosion is mostly likely redistributed over the slope itself (as evidenced by numerous deposition results of plot measurements). One year after re-sloping, measured erosion becomes almost insignificant as fine particles have been deposited in voids in the waste rock. Within the limits of the waste dump design parameters studied, there appears to be no reason to establish design criteria from the standpoint of erosion control. There was also no evidence to support the need for erosion intercepts (dozer cuts located diagonally across the slope face), supported by the result from the long, undisturbed Slope 2 at Tent Mountain.