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38 Using an average seam thickness of 5,86 ft, a trench width of 100 ft, a coal density of 80 lbs/f t3, and a mean production rate of 510,000 tons/yr, the rate at which the trench is extended is 50 ft/day, On the average, the maximum length of open trench 'in Pit A will be 3000 ft, a length that will be achieved in some 60 days, assuming the average conditions presented above apply at the outset of mining. For the purposes of pit inflow estimates, it is further assumed that overburden removal in Pit B is initiated at the beginning of the second year and that the trench length is extended at the rate of 50 ft/day. Under these conditions, the maximum length of open trench at any time is 6000 ft. Inflow to the pit will occur from both sides and the ends. However, the area of aquifer exposed on the end of the trench is very small relative to the area exposed on the lateral surfaces of the pit, and inflow from the end of the trench was neglected, therefore. Depending upon the final mining plan, there is one area in Pit A where the eastern extremity of 1 the. pit may intersect the old stream deposits in Ennis Draw_ Potential inflow for this case will be discussed subsequently. Regardless of whether the aquifers are confined or unconfined initially, the exposure of the aquifers in the pit will cause the aquifers to become unconfined in the vicinity of the pit. Therefore, the aquifers will respond according to a coefficient of storage (apparent specific yield) characteristic of unconfined materials. Also, exposure of the aquifers in the pit causes the boundary condition on the outflow face of the aquifers to be that of atmospheric pressure. Because individual aquifers in the overburden could not be identified, the interval extend- ing from the bottom of the coal seam to the existing piezometric surface was regarded as the initial saturated thickness. The saturated thickness i