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• <br />Section 779.14(a) Continued. Rule 2.04.6 <br />plan area. However, they do correspond to some of the geologic units <br />found in the permit area. Two (2) of these holes, DH-3A and DH-4, shown <br />on the Kerr Mine Area Geology Map (Map 6a) are located in the Kerr permit <br />area, but were drilled into geologic strata considerably below that to be <br />impacted by mining. Therefore, the data from these holes has not been <br />incorporated in this evaluation. Since a considerable amount of <br />geochemical and plant response data was generated in the USGS effort, the <br />results of the Kerr data are compared to the USGS data where appropriate. <br />A further discussion of this data is presented in Section 779.21. <br />Additional relevant research was conducted by the BLM on the EMRIA <br />Revegetation Study Plots located on the southern end of Pit 1. fifty <br />samples were collected by Scott Fisher, now of OSM, and analyzed for a <br />number of important soil and plant tissue parameters. These data are <br />• somewhat limited in value for some parameters due to the lack of an <br />adequate description of the laboratory methods utilized in the analysis <br />of the data. However, to the extent that the results of this study are <br />consistent with the Kerr and USGS data they will be discussed in the <br />following narrative. The results of the BLM study are presented in Table <br />B0, BLM Test Plot - Preharvest Analysis for Regraded Spoil and Table 81, <br />8LM Test Plot - Postharvest Analysis for Regraded Spoil. <br />jtesults of Geochemical Testing <br />Ammonium (NH.-N). A total of 67 Kerr overburden samples were originally <br />analyzed for ammonium. The mean value was 42.12 ppm for ammonium with a <br />range of 1.90 to 99.80 ppm. The weighted mean, reflecting the thickness <br />of the strata represented by each sample, for ammonium was 34.83 ppm. The <br />arithmetic mean value of 25.54 ppm was calculated for ammonium in the <br />proposed mine plan area. Although previous attempts have been made to <br />quantify suspect values for overburden ammonium concentrations, at the <br />present time (Berg, 1981 and OTA, 1986) no such limits exist. In <br />summarizing the scientific literature relative to plant and water <br />toxicities Barth et.al., (1981) recommended that overburden materials <br />containing mare than 160 ppm ammonium should be considered suspect. <br />Examination of the Kerr overburden analysis results indicates that all of <br />779-18 a Revised-Apri1,1990 <br />