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Parameter Selection
<br />Overburden information from the six Phase I sample sites was evaluated and summarized to
<br />select and justify the proposed chemical and physical parameter list for the Phase II
<br />sampling program. The Phase I overburden samples were tested for paste pH, paste extract
<br />EC, saturation percentage, sodium adsorption ratio (includes water soluble sodium,
<br />calcium, and magnesium), acid base potential, ammonium oxalate extractable molybdenum,
<br />DTPA extractable cadmium, copper, iron, manganese, nickel, lead, and zinc, hot water
<br />extractable boron and selenium, and particle size (includes percent sand, silt, and clay).
<br />Four constituents (total combustible solids, nitrate-nitrite, arsenic, and mercury) listed
<br />on the Colorado Water Quality and Overburden Geochemistry Guidelines (1982) were not
<br />included on the Phase I parameter list.
<br />The Phase I analytical results from the six core holes were compared to Pea body's most
<br />recently approved overburden-spoil suitability list presented with the Nucla East permit,
<br />Tab 6, Attachment 6-1, Table 6-1-3 (Peabody Coal Company, 1988). The number of samples
<br />which exceeded suitability levels and the maximum constituent values by core are presented
<br />in Table 1.
<br />Unsuitable levels were recorded for six constituents, pH, acid base potential, iron,
<br />manganese, boron, and clay. Extremely acid soil reaction, acid base potential values with
<br />more than a five-ton calcium carbonate per 1,000 tons of spoil deficit, and boron values
<br />greater than 5 ppm were dominantly associated with the Lennox coal seam. Clay percentages
<br />greater than 50 percent were associated exclusively with shale strata overlying the Lennox
<br />coal seam and also with the 1.5-foot thick shale zone directly overlying the Wadge coal
<br />seam. Peabody suspects the excessive iron and manganese values are attributed to the core
<br />samples having been contaminated by drill stem grease.
<br />No unsuitable concentrations rvere recorded for selenium, zinc, lead, nickel, copper,
<br />cadmium, molybdenum, or sodium adsorption ratio. The maximum values recorded for lead,
<br />selenium, cadmium, and sodium adsorption ratio are an order of magnitude less than the
<br />threshold limit, while values for zinc, nickel, copper, and molybdenum are about two to
<br />five times less than threshold limits. No unsuitable values were recorded for salinity or
<br />saturation percentage; however, maximum values were less than two times the threshold
<br />value.
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