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<br />Section 779.14(a) Continued. Rule 2.04.6 <br />value of 11.27 ppm with a range from 0.12 to 71.9 ppm, The weighted mean <br />was 9.94 ppm and 3.22 ppm for the Kerr and USGS greenhouse samples, <br />respectively. <br />Ninety percent of the samples have zinc concentrations above 1.0 percent <br />which, as described by Ludwick (1976), is adequate for crop growth. Only <br />5.5 percent of the samples have values less that the "marginal" limit <br />given by Ludwick as 0.51 ppm. As described by Ludwick (1976), Heil <br />(1976), Berg (1971), and Follett and Lindsay (1970), natural zinc values <br />in Colorado are low. The Montana Guidelines have established a suspect <br />level for zinc of 40 ppm, exceeded by only three (3) of the Kerr samples. <br />On a volumetric basis only 2.6 percent of the material exceeds the suspect <br />level. Since the work of Dollhopf (1981) in Montana documents that Zn is <br />a contaminant of drilling grease it is possible that the elevated values <br />• reflect sample contamination. These values should not pose a problem with <br />respect to potential toxicities. <br />ron (Fe). A total of 54 Kerr and 66 USGS samples were analyzed for <br />iron. DTPA values for iron had an arithmetic mean of 73.39 ppm and range <br />from 7.50 to 616.0 ppm. The weighted mean for the Kerr samples was 61.15 <br />ppm and 86.10 ppm for the USGS samples. All of the samples analyzed had <br />iron concentrations above the 2.6 ppm "marginal' lower limit for plant <br />growth described by Ludwick (1976). Solute leaching of iron into <br />groundwater is expected to be minimal, due primarily to the alkaline pH <br />values of the groundwater. The mean pH of groundwater is 1.07 and would <br />not facilitate dissolution of iron. No suspect levels for iron have been <br />established by any mining guidelines (Dollhopf et. al. 1977). <br />Cooper (Cu). A total of 54 Kerr samples and 66 USGS samples were <br />analyzed for copper. The mean DTPA copper value for the Kerr samples was <br />5.26 ppm with a range from 0.88 to 13.92 ppm while the mean value for the <br />. USGS samples was 2.16 ppm with a range of 0.18 to 6.4 ppm. The weighted <br />mean value of the Kerr samples was 9.94 ppm and 2.16 ppm for the USGS <br />samples. Vaiues above 0.20 ppm are considered adequate for potential <br />topsoil suitability, from an agronomic standpoint, according to Ludwick <br />(1976). Two (2) samples representing 0.65 percent of the overburden on <br />»o_io <br /> <br />