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<br />Potential Impacts of Replaced SDOii on Ground-Water Oualtty. <br />Spoil Characterization, According to tha~Mi ping Plan for the Nucla East area, the <br />overburden and interburden maters ale will be removed and replaced as spoil material aftef <br />the loner Dakota coal is removed. The method of remval will be, at least ins daily, by <br />dozers and serapersl end therafare, mf xi ng of the overburden and inierburdan materSal will <br />be mi nimel to moderate. The spoil characters stS CS should tonslst of approximately 65.5 <br />percent serW and 34.5 shale (as calculated Fran 6 core lithologic logs). <br />The undisturbed sandstone is fine to medium graf Wed, is wail cemented and contains <br />horizontal and vertical fractures antl joints. The disturbed and replaced Benda should <br />show an Snerease in poroaSty but a sl lght decrease in parmeabtllty due to the mixing of <br />the sandstone blocks with shale. <br /> The gaochemt airy of The individual Units 1, 2, 3, and 4 vats as sli phtly in pH, and ABP, <br /> and chamlatry. Uni to 1 and 3 contain large parcentagea of 504,. Fe, and Hn and <br /> exchangeable Ce. The average pH values for Units l and 3 range tram 7.2 to 7.5. Vary <br /> minor occurrences oT chin, more acidic or basic zones de occur sporadically in looses less <br />• than O.5 ft thick . This material is tonal tlared to be stable and non-toxic. <br />Units 2 antl 4 Sn the interburden are more distinctive than the reaE of the naterial above <br />the lower Dakota coal. They era similar to the other units Sn their pradomf nonce of Fa, <br />Mn, and 504, but lack the high content of exchangeable Ca. Additionally, their ABP and pH <br />tend to ba the lowest of the others with a mean ADP of -18.4 and a pH of 6.7 for Unit 2, <br />and a Wean ABP of -24.2 and a pH of 6.0 for Unit 3. The acids ty of Chase two units is no <br />doubt due to their proximity to the upper and lower Dakota coat bads. <br />Effects on Ground-Water OuaTi ty. Mi nine of the, lwaer Dakota coal will potentially <br />change the cheml airy of the water 1n contact with the overburden/spoil through Throe <br />procea sea: <br />° Increase the exposed surface area of m7nerela <br />• Increase the oxygen content <br />° Mixing of the materials <br />17-57 Revt sad 04/11/86 <br />• <br />REVISED MARCH 2006 Attachment 2.05.6(3}2-67 <br />