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.~ r GOLD HILL VENTURES P.O. Box 1523 Longmont, Colorado 80501 ~II III~IIII~~~~~ ~I~ September 24, 1985 Mr. Peter V. O'Connor SEP 2 5 198 Mined Land Reclamation Division 1313 Sherman Street {~F,IN[ii i_ANU Denver, Colorado 80203 RECLA.fi1ATICN DIVISION RE: CASH MINE AMENDMENT -PERMIT NO. M83-141 Dear Mr. O'Connor: This letter is in response to the issues that you raised in your letter of September 20, 1985, which I received on September 23, 1985. 1. Gold Hill Ventures' consulting water resources engineers, Ted Zorich and Associates, Inc., have calculated that a 100-year/ 24-hour storm event over the precipitation catchment area would result in approximately twice the amount of water runoff of a 5-year/24-hour storm event. Because the hillside location selected for the tailings impoundment structure has such a limited precipita- tion catchment area, our consulting water resources engineers decided that drainage ditches designed to handle the 5-year/24-hour storm event would be sufficient for this site. However, if the Mined Land Reclamation Division's reclamation staff has taken the posi- tion that the diversion ditches should be sized to handle the 100-year/24-hour storm event, we will ask Ted Zorich and_ Associates, Inc., to redesign the aversion ditches to handle the larger water runoff vol~ume~ copy of your final calculations regarding the different construction requirements for these two storm events would be very useful for comparison with our data. Did your figures assume an instantaneous time of water concentra- tion? Were your calculations based upon the assumption that all of the precipitation is going to run off the precipitation catchment area? It will also be helpful to know if your calculations considered if any water would be lost due to depressions in the terrain. 2. My letter of September 23, 1985, addressed this question in some detail. However, upon examining the exploration opportunities that exist along the Who Do vein, we have concluded that the removal of 11,500 tons of waste rock from the Who Do mine dump will enable us to conduct an additional 350 feet of important under- ground exploration drifting. This amount of exploration drifting will replace the amount of waste rock removed to install the minimum two foot rock capillary barrier between the mill tailings and the topsoil medium that you deemed necessary in your letter of .~ '` t. x ~~ ~~'~~ N' u