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<br />i <br />Getty Task 2 Page 23 March 1, 1983 <br /> <br />the mine ss vertical flow. The length of time that would be required for the <br />overlying saturated xoae to drain is difficult to estimate. Actual simulation r <br />of this phenomena would require the use of a three dimensional mod_1. The ` <br />approximation utilized in the two dimensional model results is initial <br />gradients that are steeper than would actually develop across the entire <br />aquifer. The net effect of this approximation is that the initial flow rates <br />ere somewhat higher than •ill actually occur. Later inflow rates may be <br />naderestimeted however, since the drainage of the overlying aquifer material <br />cannot be proyerly accoaated for. Because the time for the overlying material <br />to drain is probably relatively short, the net effect of this approximation is <br />to slightly overestimate lateral inflow rates. <br />Although it was possible to estimate the emoaat of vertical, upward flow <br />required to maintain the groundwater monad is the vicinity of the Tiekea lease <br />as it currently exists, the model is not capable of ealcalating the increase <br />in this flow rate as the heed is the overbnrdea aquifer is reduced. The <br />inflows estimated, therefore, do not include the total amount of inflow that <br />may occur through the floor of the mine. The amount of this flow is dependent <br />oa the difference in heads between the overbnrdea sad underlying aquifers sad • <br />the vertical saturated permeability of the material between the aquifers. <br />Since neither the static head is the aaderlyiag aquifer nor the permeability <br />of the intervening unit are known, it is difficult to estimate the amount of <br />flow through the floor of the mine ceased by a redaction of head is the <br />overburden aquifer. . <br />If it is assumed that the monad is the result of fracture zones that <br />e:iend completely through the coal sad the agnitard material between aquifers <br />sad fully penetrate the underlying Troni Creek aquifer, a potential 'worst <br />case' analyses may be performed to estimate the amount of inflow that could be <br />expected through the mine floor. Sneh a feature can be analyzed as a lice <br />sink on which the dr aw down is prescribed. A definition sketch for this <br />analysis is presented oa Figure 9. The egaation for flow per unit length of <br />the sink under these eo ad itioas is presented by McWhorter sad Saaads (1977): I <br />l <br /> <br />s T _ <br /> <br />(a a t) <br />where q =inflow per unit length at time t (sq. ft./day), <br /> <br />