REP42389 - Laserfiche WebLink

Home Browse Search

excessive exchangeable sodium levels, which could potentially lead to upward migration of sodium salts which could limit vegetation growth due to direct nutritional effects or indirect soil structural effects. The publication Reclaiming Mine Soils and Overburden in the Western United States; Analytic Parameters and Procedures (1987), edited by Williams and Schuman, and published by the Soil Conservation Society of America contains a chapter on sodium, which includes a section summarizing the research on cover soil depth requirements. The generalized conclusion presented is that, if maximum grass production is the reclamation goal, at least 35 inches of coversoil should be replaced over a sodium affected spoil, although site specific considerations including the need to buffer against mine soil loss due to upward sodium migration and erosion might warrant a thicker coversoil layer. Site specific pre-disturbance soil characteristics are also referenced as factors which need to be considered in determining the appropriate cover soil depth. It is also noted that, because most of the cover depth research has focused on impacts to grass production; effects of varying coversoil depth over sodic material on vegetation cover, diversity, and shrub and forb establishment and persistence are not well documented. The long term revegetation objective for the coal waste disposal area is to establish a sagebrush/grass vegetation community. Review of soil type descriptions for soils in the affected area which supported sagebrush/grass prior to disturbance indicates that in general, the soils associated with this vegetation type are good quality loams and silt loams at least 30 inches thick. The enclosed journal article Trace Element and Salt Movement in Retorted Oil Shale Disposal Sites, by Stark and Redente (1986) may have particular relevance to the issue in question, due to the similarity of environmental conditions between the Piceance Basin study site and the Deserado Mine site. The study included 1, 2, and 3 foot topsoil cover depths over the relatively saline/sodic shale layer. The authors reported that salt movement into the soil decreased with increasing cover depth, and also reported the apparent occurrence of interface effects causing the accumulation of soluable salts in the cover soil immediately above the shale. Soil/Refuse Sampling Recommendations Apparently, none of the test plot soil sampling conducted to date has been in accordance with procedures recommended by the Division, with respect to sampling of incremental depths within specific test plot locations. It is still not entirely clear what the procedure was for the 1990 sampling. The report text states that "four samples were collected on the north and south plots. Samples were collected at the approximate center point of each plot and composited for each lift; 12 inch, 24 inch, 36 inch, and 48 inch." Was sampling limited to the 48" depth plots? Is the "12 inch lift" the soil layer directly above the refuse or the layer at the