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• inches in the refuse. These observations on rooting response in the refuse materials are inconsistent with the findings reported by Barth (1984) wherein it was reported that root growth into sodic spoil was severey restricted. Since the root growth into the sodic Southfield Mine refuse was much deeper than reported by Barth (1984) it adds credence to the notion that the sodic nature of the Southfield Mine refuse is unlike that from any of the sites evaluated in the Northern Great Plains. Thus, the abundance of root growth into the sodic refuse materials suggest that these materials do not possess the same level of adverse properties as do the sodic spoils in the North Dakota. Samples taken from respread topsoil over refuse, contain what appears to be elevated levels of sodium at the zone immediately above the soil spoil interface. For example, the 0-2, and 8-10 inch depths from the seven year old refuse site had SAR values of 4.7 and 11.3 respectively. The 41-43 inch depth from the refuse site five years old had an SAR value of 10.2. These values are all higher than the average SAR value of 2.27 associated with non coal contaminated soil. At first glance these elevated levels of sodium would suggest that upward migration of sodium might be occurring. However, examination of the exposed soil profiles and data relative to OM, Fe and Mn, three very immobile elements, confirm that these elevated levels are due to contamination of the soil with refuse. The baseline levels of OM for non coal contaminated soils average 0.60 percent while the OM Levels for the high SAR • respread soils averages 1.10 percent. Using a t-test comparison these means are signficantly different at the 0.10 level. Fe and Mn in the non coal contaminated soils average 2.81 and 1.45 ppm, respectively, while the corresponding values in the high SAR respread topsoil are 13.33 and 8.67 ppm, respectively. Using a t-test comparison of these values with the corresponding values from the non coal contaminated soils it can be determined that the means of both parameters are significantly different at the 0.001 level. The elevated values of OM, Fe and Mn values in areas where high SAR values are found, clearly suggest that mixing of the refuse and respread topsoil has occurred. Therefore, it is obvious that the elevated SAR values in the respread topsoil are a resuR of mixing and not upward sodium migration. The boundary between the refuse and respread topsoil was very irregular, with waves and streaks of refuse often seen extending several inches. upwards into the respread topsoil. During the field sampling no attempt was made to segregate these materials. The irregular boundary appears to be a resuR of the reapplication technique and accounts for the elevated sodium levels in the topsoil immediately above the refuse materials. This mixing is therefore, very similar to the mixing practices commonly used for topsoiling on sodic spoil materials in New Mexico. The two central issues which OSM and subsequently CMLRD were concerned with when mandating the four (4) foot cover requirements were the potential for upward migration of salts and acidfication. These concerns are expressed on page 15211 of the Federal Register dated March 13, 1979 . wherein R states that 'adequate cover must be applied to prevent the upward migration of toxic salts that may affect plant roots and provide a barrier to prevent oxidization of acid forming material.' virtually atl of the current refuse data suggest that there is no known possibility that the Southfield Mine refuse materials will acidify over time, thus this concern is nullified. The 45