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4.0 REGRADED SPOIL LABORATORY RESULTS In order to focus on what Trapper considered a potential spoil problem, Trapper Mine proposed and CMLRD agreed to abandon its current program for sampling in-place overburden and provide yearly analysis and reports on regraded spoils. The annual report will demonstrate that a surface spoil layer exists with acceptable physical and chemical properties. With Che addi- tion of suitable topsoil, these regraded spoils provide a suitable medium to promote plant growth and successful reclamation. 4.1 Methods Composite samples were taken on approximately 50-ft to 100-ft centers fur each mapping unit. Mapping units in 1987 were determined by visual and textural difference with no size limitation, however a minimum sampling density of approximately one sample per five acres of reclaim area will be performed in the future. Each sample was a composite from the top four inches of spoil material. Future sampling will be composite samples from one foo[ into the spoil material. The samples were analyzed for pH, EC, CaC03, O.M., N03-N, P, K, Zn, Fe, Mn, Cu, Se, Ca, Mg, Na, SAR, % Saturation, texture, Hg, F, Total S, and acid-base potential. If a large negative acid-base potential was found, then additional analysis to include pyritic Sulfur and S04-S was run for that sample. The final mapping units were then transferred to the spoil history map, M4-1. Each delineation on this map was identified as to year sampled, texture, and lab analysis number. 4.2 Results Spoil laboratory analysis was conducted by the Colorado State University Soil Testing Laboratory and are provided in Table 4-1. Interpretation of these data are presented in Table 4-2 and include verbal interpretations which are intended to describe laboratory values in relative practical terms. "Good" is used to indicate data characteristics that do not pre- sent a problem while "excessive" is used to point out which values may present a possible toxicity problem. Following is a brief description of each parameter as described in the literature and how suitability cri- teria were assigned to each. pH - Measure of the degree of acidity or alkalinity of a soil. Optimum pH values range from 6.0-8 .4 (Merritt 1983). Actual spoil pH deter- mination ranged from a low of 6.8 to a high of 8.0 (z = 7.3) on Trapper spoils. Electrical Conductivity - Conductivity is an indirect measure of the solvable salts in the soil. Optimum EC values in terms of plant growth are <4.0 (Merritt 1983). Actual spoil analysis at Trapper ranged from .4 to 3.9 (z = 1.9). cont.