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n L~ area. Given the lack of any history of combustible materials associated with the refuse piles in this area, improvements in mining efficiencies, and corresponding decreases in coal content of these refuse materials, ft is highly unlikely that any of the materials in the Southfield Mine area possess the potential to become combustible. The formation of acidic materials is another criteria involving the evaluation of cover materials over refuse. his true that pH values suggestive of acid formation are associated with four of the old refuse piles sampled during this evaluation. Unfortunately, the exact histories of these materials are unknown. An examination of these areas suggests that they contain sufficiently more waste coal materials than are presently associated with the current refuse materials. This difference in coal to waste rock means that these materials possess differing potentials for acidification. An examination of the potential acid formation of the current refuse materials using the NMMMD Guidelines for acid base potential reveals that these materials possess an extremely low potential for acidfication. In fact they contain a higher overall suitability with respect to acid base potentials than do the native soils in this area. This comparison suggests that the overall suitability of the refuse materials is significanty greater than are the native topsoil materials. Therefore, with respect to the suitability of the refuse materials from an acid formation standpoint, the refuse materials are superior to the native soil materials of the • Southfield Mine area. Potentialy toxic forming conditions are undoubtedly the largest potential area of concern associated with the Southfield Mine refuse cover materials. It should be pointed out that by regulatory definition, materials are toxic when they contain constituents in amounts that are °detrimental to biota'. Examination of the SAR values suggests that elevated sodium could potentially limit the usefulness of the refuse materials as a rooting zone material. According to reviews on the limitation of sodium (Merrill et. al. 1983b, Carlstrom et. al. 1987 and Richards 1969) the primary concerns involving sodium are adverse changes in the physical properties of the soil, although in some instances elevated sodium levels can adversely affect the nutritional balances of vegetation. According to these reviews, dispersion becomes a problem when saturation percentages exceed 90 percent, well above any of the Southfield Mine refuse materials. Extremely low hydraulic conductivity values are reported to be the "dominant factor limiting sodic spoil as a plant growth medium." Root growth into spoil under such conditions has been very restricted. Perhaps the best example is that of Barth (1984) who reported that root growth into sodic spoil was confined to the uppermost 10 cm. In the three soil p'ds dug through the respread topsoil on the reclaimed Southfield Mine refuse the maximum depth of visible rooting was measured. The pit on the top of the refuse pile was located in refuse five years old, had a thickness of the respread topsoil of 43 inches, and the refuse material was determined to have an SAR of 29.6. Roots of this location were observed . growing to a depth of 8 inches into the refuse material. At a second site where the thickness of respread topsoil was only 10 inches and the measured SAR was 11.3, roots were observed growing through the eight inches of refuse and into the fractured granitic rock below to a depth of 24 inches. At a third site covered with only two inches of respread topsoil and having an SAR of 19.6, the roots were observed growing to a depth of 24 44