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<br />Envror~t~e <br />LARRY E. O'BRIAN <br />FOUNDER <br />July 22, 2002 ` <br />Bdl McIntyre <br />Colorado Division of Water Resources <br />1313 Shermart St, #810 <br />Denver, CO 80203 <br />Dear Bill: <br />RE: Temporary Substitute Supply Plan <br />Suburban Sand tind.t3ravel <br />RECEIV E~ . , :; , <br />)UL 2 2, 2002 <br />pivislonoiMinefalsandpeale9Y .;-' <br />, <br />7985 VANCE DRIVE, SUITE 205A <br />ARMADA, COLORADO 80003 <br />303-423-7297 <br />FAX 303-423-7599 <br />ItkCE9yE+: <br />1UL`2 '! 200" <br />. WATcR RE$OURCEi: <br />' g'(ATE %NGINE=i1 <br />co!o. <br />Road Runners Rest II Gravel Pit ' <br />MLRB Permit N M-79-195 ;, - <br />The following ittfgrmation is based on Quit meeting in May 2002.regarding how to <br />calculate the Consumptive Use (CU) for the vegetation on the site and come up with net losses <br />at the mine associated With lake area. This packet contains two sets of tables showing one <br />scenario as if the dewatering pumps failed and activities ceased, leaving 100 acres of lake and <br />one scenario as if mitung prpgresaes to completion with no more than 25 acres of open water <br />during mining operatiot-s. , <br />Suburban sold this site to Denver Wate;. Department"for future Construction of a water <br />storage reservoir. The sales contract says Suburban ,has to supply evaporation makeup water <br />as long as they are minittg, .Once mining ends, Denver.will be .the responsible for the <br />evaporation loss off the laloe until the reservoir is constructed.. To the best of our knowledge, <br />no plans for reservoir design or construction have been submitted to.the OSE or D.M.G. at <br />this time. <br />In this submittal.I have tried to stay consistent with,`giir discussion as best as I could. I <br />found a CSU program, $OrttTt Plquf Conrwnptlva Urn (t^,U) Model (SPCUM) W calculated the <br />Blaney-Griddle Const~ptiye Use Humber (CU) and ysed it as the base. t'or.the <br />evapotranspiration ttumbers iq this packet. This program is more, spghisticated than my <br />approach but I feel it gives u9 a better idea of historic water u$e at the- site aS it was close to <br />my single year calculatiou;yJ in other submittals. <br />During our meeting we discussed using two methods to Caleulate the historic B-C <br />numbers for the site..One was to use the 709G x Total Ptecip. or the second was to calculate <br />the Potential Evapotranspiration (PET) for the vegetation coyer:, Since the ground ware; table <br />was within 24 i~hes of the surface prior to mining we tltgught using the PET method would <br />be most advantageous. The SPCUM program will calculated the B-C without using any input <br />water. It calculates an Irrigation Water Required (IWR) numbei•,'to show how much additional <br />water would need to be added tp.the crop, taking into accout-t the 1'sffgctive Rainfall (ER) for <br />yi <br />~i r, ~~.~ <br />