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DocuSign Envelope ID: EBE28081 -B782-4B42-BADB-D8C93B687B1 B <br />December 22, 2020 <br />Angela Aalbers <br />Page 2 of 12 <br />Reference: East Taylor Seep Investigation <br />Table 1 Colowyo Monthly Climate Data <br />Month <br />Minimum <br />(in) <br />Average <br />(in) <br />Maximum <br />(in) <br />Craig Station <br />2020 (in) <br />Evaporation a, b <br />(in) <br />Net Evaporation <br />(in) <br />Jan <br />0.2 <br />0.65 <br />1.67 <br />2.09 <br />0 <br />-0.65 <br />Feb <br />1 0.41 <br />0.89 <br />1.85 <br />0.78 <br />0 <br />-0.89 <br />Mar <br />0.52 <br />1.43 <br />2.71 <br />1.38 <br />0 <br />-1.43 <br />Apr <br />0.87 <br />1.83 <br />3.45 <br />0.73 <br />0 <br />-1.83 <br />May <br />0.41 <br />1.87 <br />3.32 <br />2.23 <br />4.96 <br />3.09 <br />Jun <br />0 <br />0.68 <br />3.25 <br />0.78 <br />6.56 <br />5.88 <br />Jul <br />0.5 <br />1.21 <br />2.28 <br />0.61 <br />6.93 <br />5.72 <br />Aug <br />0.25 <br />0.95 <br />3.11 <br />0.92 <br />5.90 <br />4.95 <br />Sep <br />0.12 <br />1.17 <br />2.7 <br />0.28 <br />4.65 <br />3.48 <br />Oct <br />0.06 <br />1.53 <br />2.65 <br />0.86 <br />2.90 <br />1.37 <br />Nov <br />0.12 <br />0.76 <br />1.4 <br />0.43 <br />0 <br />-0.76 <br />Dec <br />0.07 <br />0.83 <br />2.75 <br />0.01 <br />0 <br />-0.83 <br />Total <br />3.53 <br />13.784 <br />31.14 <br />11.10 <br />31.90 <br />18.1 <br />8 WRCC 2020 <br />b Green Mountain Dam Station <br />° Calculated from site average precipitation and evaporation data <br />d WtJnderground Woodbury - KCOCRAIG7 <br />Site Conditions <br />The watershed contributing to the East Taylor Pond is approximately 1,076 acres, and this area was <br />previously mined and is in the process of being reclaimed. The area was mined as an open pit from 1995 to <br />2002, and highwall mining occurred from 2005 to 2010. The area was backfilled and reclaimed starting in <br />2011. Mine data suggest the ends of the highwall miner holes are within 50 horizontal feet and 20 vertical feet <br />of the Taylor Creek stream channel. Approximately 300 acres remain disturbed, and approximately 86 acres <br />were reclaimed in the last couple of years. The remaining 690 acres have been reclaimed for several years. <br />Reclaimed areas are vegetated with grasses. Runoff is collected in ditches and conveyed to the East Taylor <br />Pond, where sediment is removed before the water is discharged through Outfall 010 to Taylor Creek. There <br />are additional sediment ponds located at the boundary between disturbed and reclaimed areas. In general, <br />runoff and infiltration from disturbed and newly reclaimed areas is expected to be higher than reclaimed and <br />native areas due to there being little to no evapotranspiration. Most of the precipitation runs off via the ditch <br />network. Research has shown that infiltration and runoff from areas that have been reclaimed for several <br />years mimics native conditions (Sanchez 1988 and OSMRE 2016). Therefore, the 690 reclaimed acres are <br />assumed to have reached their final condition regarding the water balance. As the remaining 386 acres are <br />reclaimed and vegetation grows, infiltration and runoff are expected to decrease. Figure 1 below shows the <br />project area with the East Taylor Pond and Seep at the north end of the watershed and the disturbed areas at <br />the south end of the watershed. The disturbance/pit extents are also shown. <br />Design with community in mind <br />pk c:\users\pkos\documents\_projects\colowyo\easttaylorseepwaterbalance_22dec2020_final.docx <br />