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-17- The alluvial valley floor reconnaissance level survey identified I6.3 acres of unconsolidated alluvial deposits along Raton Creek, downstream of Starkville Gulch (see afap No. 16 of the permit application). On the basis of infor- mation supplied by the applicant, the Division has determined that these deposits constitute an alluvial valley floor. The following discussion presents findings of the Division with regard to the potential impacts of the operation on this alluvial valley floor. Alluvial Valley Floor Findings with Regard to Farming The 16.3 acres of unconsolidated streamlaid deposits are considered to be undeveloped rangeland. No farming activities are currently being practiced in this area. Additionally, a representative of the Soil Conservation Service (SCS) has stated that farming activities on Less than 20 acres of alluvial valley floor is not common practice in Las Animas County. The SCS representative also predicts that this area will only support approximately one animal unit (cow with calf) for a period of two months. The operation will not physically impact any portion of the alluvial valley floor. The alluvial valley floor is not included within the permit area. Therefore, pursuant to Rule 2.06.8(5)(1), the Division finds that the proposed surface coal mining operations will not interrupt, discontinue, or preclude farming on an alluvial valley floor. Alluvial Valley Floor Findings with Regard to Material Damage to Water Quality and Quantity The potential for diminution of water quality in the Raton Creek system is a function of the effect of the operation on surface water and ground water quality. Impacts on surface water quality could result from surface runoff from disturbed areas which experience an increase in total dissolved solids (TDS) and total suspended solids (TSS)_through contact with recently exposed, unweathered material. Most of the impact due to increases in TSS will be mitigated by the sedimentation pond. Runoff from the disturbed area will be routed through the sedimentation pond which is designed to affect precipitation of suspended particles. Rny water discharged from the pond will be monitored to detect significant increases in TSS. Flow measurements recorded in the spring of 1982 for Starkville Gulch and Raton Creek indicate a dilution factor of 1:64. This means that an increase of 63 mg/1 of any constituents of TDS would result in an increased concen- tration in Raton Creek of approximately 1 mg/1. An increase of this magnitude would not significantly impact quality of water supplied to the alluvial valley floor.