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<br />Mr. Nathan D. Phelps, P.E. August 18, 2017 <br /> Page 2 of 5 <br />that result from mining related exposure of groundwater. The DRMS letter identified four <br />approaches to satisfy this requirement. In accordance with approach nos. 1 and 3, you have <br />indicated that a bond has been obtained for $175,334 through the DRMS to assure that <br />depletions from groundwater evaporation do not occur in the unforeseen event, or events, <br />that would lead to the abandonment of the North River Pit. <br /> <br />DEPLETIONS <br /> <br />Since no mining is planned during 2017, pond evaporation will be the only water demand at <br />the site. During the past year, portions of the north pond have been backfilled, reducing the <br />total water surface area. The total water surface area for the two ponds at the site was 8.06 <br />acres and has been decreased to 6.88 acres (Figure 2). For the purpose of this SWSP, you <br />determined the evaporation from the 6.88 acres to be 27.66 acre-feet, based on a net annual <br />evaporation of 4.02 feet from the Lower Arkansas Water Management Association’s <br />(“LAWMA”) decree in Case No. 2002CW181. A Glover analysis was used to estimate the timing <br />of stream depletions with the following parameters: <br /> <br /> Transmissivity (T): 142,000 gpd/ft <br /> Specific Yield (S): 0.2 <br /> Distance of river (X): 500 feet <br /> Distance to no-flow boundary (B): 4,800 feet <br /> <br />Although these parameters were accepted for this SWSP approval, you will be required to <br />provide justification for the distances used in the Glover analysis in any renewal request <br />submitted for this SWSP. Please note that the distance to the river should be measured as <br />the distance from the centroid of the exposed surface area(s) to the river. <br /> <br />According to the Glover analysis, 95 percent of depletions were modeled to accrue to the <br />stream within the first 12 months; therefore, a 12 month unit response function will be used <br />to calculate lagged depletions for the purposes of this SWSP, as shown below: <br /> <br />Unit Response Function <br />Month 1 Month 2 Month 3 Month 4 Month 5 Month 6 <br />0.7479 0.1577 0.0348 0.0172 0.0114 0.0078 <br />Month 7 Month 8 Month 9 Month 10 Month 11 Month 12 <br />0.0061 0.0048 0.0038 0.0033 0.0027 0.0025 <br /> <br />The results of the Glover analysis are shown in Table 1, attached, and total stream depletions <br />for the 2017 plan year are expected to be 27.78 acre-feet. <br /> <br />REPLACEMENTS <br /> <br />All-Rite leased fully consumable water from AGUA and will use this leased water as the source <br />of replacement water through March 31, 2018. A copy of the current lease for up to 28 acre- <br />feet for the period ending March 31, 2018 was provided with the SWSP request and is <br />attached to this letter. <br /> <br /> <br />