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[n association with RN-06 and TR-I5, the operator prepared a mass balance evaluation to assess <br />the effects of irrigation season mine water discharge on the salinity (conductivity) of East Salt <br />Creek water downstream from the point where discharge water enters the stream. The evaluation <br />included data from the 2001 through 2005 irrigation seasons. During four of the five years, <br />conductivity levels were reduced due to dilution by lower conductivity mine discharge water. <br />During one of the 5 years (2005) there was a slight, but insignificant (0.2%; 0.004 mmho) <br />increase. Over the five year period, there was an over-all 10.9% reduction in irrigation season <br />conductivity on East Salt Creek downstream of the mine, resulting from minewater discharge. <br />These results confirm that mine discharge is not causing a deleterious increase in stream salinity <br />levels. <br />IIL TOPSOIL <br />Soils resource information, including soil series descriptions, and evaluation of mine bench <br />materials for use as plant growth medium is provided in Section 4.4 of the permit application. <br />Information on topsoil management is provided in Sections 2.3 and 3.2, and information on topsoil <br />replacement is provided in Section 3.3. <br />No topsoil was stripped prior to mine bench and haul road construction, as this disturbance <br />occurred prior to the enactment of the Surface Mining Control and Reclamation Act (SMCRA). <br />Topsoil was salvaged from subsequently disturbed areas including the sediment pond, riprap <br />stockpile, and office facility aeeas, and, with the exception of one small azea addressed below, will <br />be salvaged from approved disturbance areas where construction has not yet been initiated. <br />Figure 2.2-2 (Surface Facilities Map), shows site specific mapping of soils at an Order 1 or I[ level <br />of intensity. The mapping indicates that soils in the vicinity of the sediment pond and riprap <br />stockpile were Rivra Gravelly Sandy Loam Vaziant, and Nihill Loam, and office facility soils were <br />Glendive Sandy Loam. Soils to be affected by the proposed McClane to Munger haul road are <br />mapped as Glendive Sandy Loam, and a small area of Rivra Gravelly Sandy Loam. A small area <br />to be affected by the proposed realignment of the access road segment at the junction with the <br />state highway is mapped as Havre Loam, saline phase. <br />Twelve (12) to eighteen (18) inches of soil were salvaged from the sediment pond and riprap <br />stockpile area, and 24 inches of soil were salvaged from the office area. <br />Information in Tables 4.4-1 through 4.4-6 documents the suitability of affected soil types by <br />horizon. Upper horizons of the affected soil types are generally good growth media, with the <br />exception of the Havre Loam, which exhibits SAR values in excess of 40, within each sampled <br />horizon below a depth of 1.5 inches. <br />Because no topsoil was salvaged initially, portions of the reclaimed mine bench access/haul road <br />may not be topsoiled upon final reclamation, and the mixed soils and overburden material in the <br />bench and outslopes would be used as plant growth medium for final reclamation. Section 4.4.5.4 <br />summarizes evaluation of the surficial and subsurface bench materials required by the Division <br />through stipulations attached to the 1982 and 1985 permit approvals. Analyses submitted in <br />response to the stipulations demonstrated that the material would be suitable for plant growth, and <br />that no special handling would be required. <br />Upon final reclamation, topsoil will be re-spread to a minimum depth of 24 inches in the office <br />azea, and 4 to 8 inches on other post-law disturbance areas and approximately 1 acre of the mine <br />19 <br />