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DocuSign Envelope ID: EBE28081 -B782-4B42-BADB-D8C93B687B1 B <br />December 22, 2020 <br />Angela Aalbers <br />Page 6 of 12 <br />Reference: East Taylor Seep Investigation <br />350 <br />300 <br />250 <br />E <br />a <br />w 200 <br />v <br />150 <br />0 <br />LL <br />100 <br />49 <br />0 <br />Figure 3 Calculated Seep Discharge Rates <br />Monthly Flow Rate vs. Infiltration <br />Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec <br />2.6% <br />7.5% <br />20% <br />Seep Flow <br />2020 <br />2030 <br />Figure 3 presents several water balance calculations, and while there is a lot of information presented, the <br />key point to consider is that the observed flows exceed all of the calculated values. Even under fully <br />reclaimed conditions, the seep will likely have flow rates that exceed 50 gpm. <br />Flow Monitoring <br />At the start of the project, available flow data were limited to discharge measurements associated with <br />NPDES permitting requirements, and these measurements were recorded at Outfall 010, which includes <br />commingled seep flows and runoff waters. The outfall flow data are shown in Figure 4 below. The flow rates <br />changed significantly in 2017, likely as the contributing watershed increased as the mining area was <br />reclaimed. Since then, the flows have shown seasonal fluctuations that follow precipitation trends. <br />Throughout the data history, sudden increases have occurred, and these are assumed to be discharges that <br />resulted from precipitation events. The seasonal low flows of approximately 140 gpm are assumed to <br />represent seep flows during the drier summer months. It is unknown if the increase in flow in late summer to <br />fall is solely the result runoff or if the seep flow also increases. <br />Design with community in mind <br />pk c:\users\pkos\documents\_projects\colowyo\easttaylorseepwaterbalance_22dec2020_final.docx <br />