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4-9 <br />' with the 2,000 pounds per day and 350 tone per year salinity limitations are estimated to be <br />$5,700,000 for the two current discharges end $17,600,000 for all three discharges. These costa <br />are based on evaporation and treatment of approximately 35 gallons per minute end 110 <br />gallons per minute for the two current discharges and all three discharges respectively, and <br />' similar construction limitations. <br />4.4.4 MA5 - On-Site Management Utilizine Assisted Evaporation With no Discharee <br />' 4.4.4.1 Description of Management Alternative <br />Mine discharges would be collected and routed to an on-site evaporative surface impoundment <br />' as described in Section 4.4.3.1. However, under this management alternative the normal lake <br />evaporation rate of 40 inches of water per year will be mechanically increased to approximately <br />' 200 inches oC water per year. The 400 percent increase in evaporation rate will be achieved <br />utilizing a diffuse aeration process. The diffuse aeration process would consist of placing <br />' sections of perforated pipe in the impoundments) and using compressed air. <br />The surface area of the impoundments) required to evaporate the anticipated flow of 140 <br />gallons per minute (salt elimination) and 35 gallons per minute (salt minimization) from the <br />two current discharges would be approximately 12 and 3 acres in size at a depth of 6 feet, <br />respectively. The surface area of the impoundments) required to evaporate the anticipated <br />' flow of 290 gallons per minute (salt elimination) and 110 gallons per minute (salt minimiza- <br />tion) for all three discharges would be approximately 25 and 9 acres is size respectively. <br />' The major work activities associated with this management alternative include the following. <br />• Construction of equalization surface impoundment(s). <br />' Construction of single or multiple evaporative surface impound- <br />ments. <br />' Installation of support piping and pumping systems. <br />• Installation of diffuse aeration system including multiple corn- <br />, pressore and perforated piping. <br /> <br />1 <br />