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Cross Gold Mine <br />December 2024 K-6 <br /> <br /> <br />The 100-YR 24-HR storm event for the area is 4.55 inches according to NOAA Atlas 14. The maximum <br />snow depth measured at Lake Eldora is 66-inches, for a SWE of 33.4 inches. <br />According to research conducted at Niwot Ridge by the University of Colorado, the average sublimation <br />rate ranges from 0.4 to 0.7 mm/day, or roughly 0.016 to 0.028 inches/day. Conservatively assuming <br />snow presence from October 15 to May 15 each winter (213 days), average annual sublimation is 4.7 <br />inches. <br />Based on the climate data described above, the water balance for storm events and snowfall is: <br />Storm Event 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 𝑅𝑅𝐹𝐹𝑅𝑅𝑅𝑅𝑅𝑅𝐹𝐹𝐹𝐹𝐹𝐹=100𝑌𝑌𝑅𝑅24𝐻𝐻𝑅𝑅𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆=4.55 𝑅𝑅𝑖𝑖𝑖𝑖ℎ𝐹𝐹𝑒𝑒 = 𝟒𝟒.𝟓𝟓𝟓𝟓 𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊 𝒐𝒐𝒐𝒐 𝒐𝒐𝒇𝒇𝒊𝒊𝒊𝒊𝒇𝒇𝒐𝒐𝒇𝒇𝒇𝒇𝒇𝒇 𝒇𝒇𝒊𝒊𝒓𝒓𝒓𝒓𝒊𝒊𝒇𝒇𝒊𝒊𝒇𝒇 <br />Snowfall 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 𝑅𝑅𝐹𝐹𝑅𝑅𝑅𝑅𝑅𝑅𝐹𝐹𝐹𝐹𝐹𝐹=𝐴𝐴𝐴𝐴𝐴𝐴.𝐴𝐴𝑖𝑖𝑖𝑖𝑅𝑅𝐹𝐹𝐴𝐴𝐴𝐴𝑖𝑖𝐹𝐹𝐴𝐴𝐴𝐴𝐹𝐹𝐴𝐴𝐴𝐴(𝐴𝐴𝑆𝑆𝑆𝑆)−𝐴𝐴𝑅𝑅𝐹𝐹𝐴𝐴𝑅𝑅𝑆𝑆𝐹𝐹𝑆𝑆𝑅𝑅𝐹𝐹𝑖𝑖−= 33.4 𝑅𝑅𝑖𝑖𝑖𝑖ℎ𝐹𝐹𝑒𝑒 − 4.7 𝑅𝑅𝑖𝑖𝑖𝑖ℎ𝐹𝐹𝑒𝑒 =28.7 𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊 𝒐𝒐𝒐𝒐 𝒐𝒐𝒇𝒇𝒊𝒊𝒊𝒊𝒇𝒇𝒐𝒐𝒇𝒇𝒇𝒇𝒇𝒇 𝒇𝒇𝒊𝒊𝒓𝒓𝒓𝒓𝒊𝒊𝒇𝒇𝒊𝒊𝒇𝒇 <br />Based on the water balance, at least 30-inches of freeboard should be maintained in each pond at all <br />times. Given that no pond is used to handle anything but mine water or stormwater, maintaining <br />freeboard is simply a matter of maintaining water movement through the ponds during the summer and <br />ensuring that the ponds are cleared of standing water before they freeze in the winter.