Laserfiche WebLink
Mr. Dick Wolfe, P.E. <br />December 31, 2010 <br />Page 2 <br />However, we have calculated the actual pond surface area to be closer to approximately 3.0 <br />acres. Conservatively, replacements will continue to be made on 4.0 acres. <br />In previous years, RBK Construction has prepared for upcoming plan years anticipating use of <br />the Baxter Road Pit for mining. Each year since the 2003 plan year, and continued for the 2010 <br />plan year, due to the lack of replacement water availability, RBK Construction plans to cover the <br />evaporative depletions on the Baxter Road Pit and does not anticipate use of the pit for mining. <br />Submittal of monthly accounting will not be required because without operational uses, the <br />monthly replacement schedule for evaporation will remain as set forth in this letter report and <br />will not require updating throughout the 2011 plan year. <br />However, it is possible that MAGUA may obtain additional replacement water later in the year, <br />which may provide the opportunity for RBK Construction to utilize the Baxter Road Pit for <br />mining if needed. If additional replacement water becomes available, RBK Construction would <br />like to reserve the option to submit an amendment to the plan to include mining operations. If <br />an amendment is requested, detailed use, consumption, proposed lagged stream depletions, <br />monthly accounting and replacement water operations will be addressed in the amendment. <br />EVAPORATION <br />During the 2011 plan year, evaporation will occur from a maximum of 4.0 acres of exposed <br />water surface. The gross annual evaporation at the Baxter Road Pit is approximately 51 inches <br />according to NOAA Technical Report NWS 33, Evaporation Atlas for the Contiguous 48 United <br />States (Map 3). Monthly evaporative losses are determined using percentages specified by the <br />State Engineer's Office for locations below 6,500 feet. The nearest weather station is Pueblo <br />WSO AP located at the airport east of Pueblo, Colorado where the 1969-1998 average annual <br />precipitation is 11.13 inches as reported in the NOAA Climatological Data Annual Summary, <br />Colorado 1998. Copies of the evaporation and precipitation sources have been previously <br />provided. <br />Effective precipitation, that part of historical precipitation that was consumed by vegetation on <br />the land to be covered by water surface, is conservatively estimated to be 70 percent of the total <br />precipitation. The annual average effective precipitation at the Baxter Road Pit is estimated to be <br />7.79 inches. Subtracting the effective precipitation from the gross evaporation yields a net <br />annual evaporation of 43.21 inches, or 14.40 acre-feet per year for 4.0 acres of water surface. <br />Table 1 shows the determination of net evaporative losses.