1992-07-22_GENERAL DOCUMENTS - C1981017

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-42- The impact of all mine discharges on the salt load to the Roaring Fork River can be calculated assuming a worse case mine discharge and average salt content. The salt load to the Roaring Fork River from mine discharges would be increased by 2.2 mg/l . This is 0.8% of the mean annual salt load normally carried by the Roaring Fork River. This should not cause any measurable change in the water quality of the Roaring Fork River. The mine discharges are not anticipated to change the ionic characteristics of the Roaring Fork River. Total discharges are a small portion of total flow (0.06% mean annual), and do not exhibit significantly different characteristics. Trace elements and heavy metals are also not found in any high concentrations which would affect the quality in the Roaring Fork River. Any elevated levels will be diluted. With satisfactory resolution of the stipulations, the Division finds that pursuant to Rule 2.07.6(2)(c)the proposed operation will minimize effects to the prevailing hydrologic balance outside the permit area. VIII. Alluvial Valley Floors - Rules 2.06.8 and 4.24 The applicant's alluvial valley floor section in Section III-E, Volume 5 and environmental resource information in Chapter III, Volumes 4, 5, and 6 of the application were reviewed for compliance. The applicant has identified no unconsolidated streamlaid deposits within and adjacent to the mine site permit area which meet the minimum size requirement of 50 feet wide and ten acres in extent as set by the OSM alluvial valley floor guidelines. This was verified by the Division through review of the material submitted and in the field. However, the Division identified an area adjacent to the load-out facility which meets the geomorphic criteria for an alluvial valley floor. This area is presently in agricultural use and is irrigated with some indications that portions are subirrigated. Since the applicant has supplied no information on this area, the Division will assume that this is a significant alluvial valley floor. The alluvial valley floor, as identified by the Division (see attached map) , is approximately 1,000 acres in extent. The train load-out facility has been in existence since 1956. Therefore, pursuant to Rule 2.06.8(5)(a)(i)(b) , the applicant is grandf athered from interrupting, discontinuing, or precluding farming and from materially damaging the quantity and quality of water in the surface and ground water systems that supply the alluvial valley floor. Therefore, the only finding which the Division is required to make is that the proposed surface coal mining operations will be conducted to preserve the essential hydrologic functions of the alluvial valley floor. No part of the load-out facility is physically located on the alluvial valley floor. Therefore, the proposed operation will not affect the natural , geologic, and hydrologic characteristics of the alluvial valley floor. In addition, the load-out facility is not expected to affect the quantity and quality of surface and ground water that supply the alluvial valley floor.