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The younger terrace deposit (Qt3) occurs only within the • extreme southern portion of the study area. Kinney reports this much younger terrace to be 30-40 feet above the present stream channel of the Michigan River. Field examination of this terrace indicated that it is a lowland area which has been flood irrigated in the past for agricultural purposes. Also, there is a reasonably good contact between the edge of the terrace and the surrounding hillsides. This second terrace deposit could, therefore, be class- ified as a potential alluvial valley floor based on geomorphic criteria. Since this area does not lie within the watershed region which passes through the proposed permit area, surface water supply into the region will not be affected by mining. Also, any potential groundwater recharge areas up dip will not be disturbed. Only two major drainage courses exist within the study area. They are Bolton Draw and Bush Draw, both of which are designated as intermittent drainages on the U.S.G.S. 7~" quadrangle maps. Since Bush Draw does not drain the proposed permit area, and is • some distance north on the west flank of the anticline, neither surface nor groundwater regimes will be influenced by the proposed mining activity. Attention was placed, therefore, on identifying potential alluvial valley floor characteristics in Bolton Draw, as this course drains the mine area. Field examination of the main Bolton Draw drainage indicates that is is a potential alluvial valley floor based on geomorphic characteristics. Bolton Draw has an identifiable stream channel and an active flood plain. The active flood plain, which is mapped as Qal on the Map of Unconsolidated Surficial Deposits (see end of this report), is usually 100-200 feet wide and consists of locally derived clay and silt. No alluvial gravels derived from the older terrace gravels are present in the headwaters region. -108-