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Newmont Goldcorp . <br /> VLF/OSA Closure Stormwater Analysis ■ <br /> NewFields Project No.475.0106.035 <br /> November 8,2019 <br /> 1. INTRODUCTION <br /> NewFields was commissioned by Newmont Goldcorp's Cripple Creek and Victor Gold Mining <br /> Company (CC&V) to evaluate the closure stormwater designs in support of Amendment 13 for <br /> the following facilities: <br /> ➢ East Cresson Overburden Storage Area (ECOSA), <br /> ➢ Squaw Gulch Overburden Storage Area (SGOSA), <br /> ➢ Valley Leach Facility 2 (VLF2), <br /> ➢ Valley Leach Facility 1 (VLF1), <br /> ➢ Wild Horse Extension Pit Backfill (WHEX), and <br /> ➢ Schist Island Pit Backfill. <br /> The conclusions are presented herein. <br /> 2. ASSUMED CONDITIONS OF THE FACILITIES AT CLOSURE <br /> NewFields worked with CC&V to develop revised closure grading plans for each facility using the <br /> following criteria: <br /> ➢ An average side slope of 2.5H:1V on all facilities. <br /> ➢ 12-foot wide bench graded in every 150 vertical feet on the OSA's. <br /> ➢ 25-foot wide bench graded in every 150 vertical feet on the VLF's. <br /> ➢ Minimum 1%grade at the top of closure surface; 1.5% grade for ECOSA and WHEX. <br /> 2.1. East Cresson Overburden Storage Area <br /> The closure design surface for the ECOSA was developed using the ultimate stacking plan created <br /> by CC&V, has a maximum elevation of 10,960 feet and is sloped at a 1.5%grade to the southwest <br /> in order to minimize runoff to Grassy Creek on the east.The closure surface also includes material <br /> from the ECOSA midway expansion. The northern section of ECOSA closure surface includes a <br /> portion on top of the WHEX Pit Backfill. During the reclamation regrading activities, the <br /> contractor shall vary the closure grades in order to generate more irregular landforms. The <br /> proposed grading plan can be seen on Figure 2. <br /> 2.2. Wild Horse Extension Pit Backfill <br /> The closure grading for the WHEX pit backfill is designed to minimize runoff to Grassy Creek on <br /> the east and was developed by CC&V. The top of the WHEX backfill has a maximum elevation of <br /> 10,325 feet and is sloped to the west at a 1.5%grade. The southern portion of the WHEX backfill <br /> will be covered by the ECOSA closure surface. During the reclamation regrading activities, the <br /> Page 1 <br />