Laserfiche WebLink
~ ~~ <br /> r o <br /> ~~ ~ y <br /> ~ <br />~ <br /> Potential Impacts of Replaced Spoil on Cround-Water Quality. <br />µ <br />~ <br /> 1 <br />~ <br /> Spoil ~~ <br />~ <br />Characterization. According to the Mining Plan for th Nucl <br />~ a Eas <br />rea , the <br /> overburden and interburden materials will be removed and replaced as spoil material after <br /> the lower Dakota coal is removed. The method of removal will be, at least initiall y, by <br /> dozers and scrapers; and therefore, mixing of the overburden and interburden material will <br />be minimal to moderate. The spoil characteristics should consist of approximately 65.5 <br />percent sand and 34.5 shale (as calculated from 6 core lath ologic logs). <br />The undisturbed sandstone is fine to medium grained, is well cemented and contains <br />horizontal and vertical fractures and joints. The disturbed and replaced sands should <br />show an increase in porosity but a slight decrease in permeability due to the mixing of <br />the sandstone blocks with shale. <br />The geochemistry of the individual Units 1, 2, 3, and 4 varies slightly in pH, and ABP, <br />and chemistry. Units 1 and 3 contain large percentages of 504, Fe, and Mn and <br />exchangeable Ca. The average pH values for Units 1 and 3 range from 7.2 to 7.5. Very <br />• minor occurrences of thin, more acidic or basic zones do occur sporadically in lenses less <br />than 0.5 ft thick. This material is considered to be stable and non-toxic. <br />Units 2 and 4 in the interburden are more dtstinttive than the rest of the material above <br />the lower Dakota coal. They are similar to the other units in their predominance of Fe, <br />Mn, and 504, but lack the high content of exchangeable Ca. Additionally, their ABP and pH <br />tend to be the lowest of the others with a mean ABP of -18.4 and a pH of 6.7 for Unit 2, <br />and a mean ABP of -24.2 and a pH of 6.0 for Unit 3. The acidity of these two units is no <br />doubt due to their proximity tc the upper and lower Dakota coal beds. <br />Effects on Cround-Water Quality. Mining of the lower Dakota coal will potentially <br />change the chemistry of the water in contact with the overburden/spoil through three <br />processes: <br />° Increase the exposed surface area of minerals <br />° Increase the oxygen content <br />Mixing of the materials <br />17-57 Revised 04/11/88 <br />