Laserfiche WebLink
Page 2 <br />December 19, 2013 <br />2. What is the possibility of the infiltration of the two outfalls creating new outfall(s) on the slope below <br />the lower bench? If a new outfall is created what action will be taken by the operator to address this <br />issue? <br />Response: <br />The possibility of the infiltration of the two outfalls to create new outfall(s) is very low. This is <br />demonstrated by the permeability testing data presented in Technical Revision No. 8 application. W WL <br />conducted additional permeability testing in the waste rock of the lower bench in support of this <br />response. The permeability testing was conducted using a ring infiltrometer method in the bottom of <br />three excavated test pits on the bench. The field method was identical to that used on the surface of the <br />lower bench, the data for which were presented in Table 5 of the Technical Revision No. 8 application. <br />Table 1 presents the results of the infiltration tests in the test pits. <br />Table 1. Results of Infiltration Tests in Excavated Test Pits on Logan Wash Mine Lower Bench <br />The results of the infiltration tests in the test pits indicate good to excellent infiltration properties of the <br />waste rock material with calculated required surface areas of 0.80 ft2 to7 ft' to accommodate infiltration <br />of a 3 gallon per minute discharge. The average for the area needed for a 3 gpm discharge for all of the <br />tests conducted is 2.5 ft . The proposed constructed infiltration trenches will be at least 30 ft. long by 4 <br />ft. wide, an area of 120 W. This is over 48 times the average calculated area needed, and based on the <br />average calculated flux, would accommodate infiltration of approximately 360 gpm. <br />On the basis of the above infiltration tests, it is improbable that the discharging mine water will result in <br />outfalls cascading off the lower bench or discharging from the slope below the lower bench and into <br />Dry Gulch. It is likely that the underlying native colluvium is of sufficient permeability to transmit the <br />infiltrating mine water to the underlying colluvial aquifer. If such an outfall was to develop, OOSI <br />would remedy the situation by scarifying the existing trenches to enhance infiltration, expanding the <br />size of the infiltration trenches, or relocating the infiltration trenches. Other actions would be taken to <br />prevent the occurrence of surface discharge that constitutes an outfall. <br />3. Please sped whether or not leaching of hazardous or toxic constituents from the waste rock will <br />occur. How does the operator propose to determine whether or not this will be an issue? In the case <br />that leaching does occur what will be done to address the issue? <br />Warsha11121713.doc <br />Test Elapsed Time <br />Volume <br />Infiltration Rate <br />Flux <br />Area Needed for <br />Test Location <br />(min) <br />(sec) <br />(total min) <br />(gal) <br />(ft?) <br />(gal /min) <br />(ft3 /sec) <br />gal /min /fe <br />3 gal /min discharge (fe) <br />Test Pit No. 1 <br />Test 1 <br />2 <br />579 <br />2 965 <br />1 0 <br />0 134 <br />0 337 <br />0000751 <br />0429641 <br />6 982575 <br />Test 2 <br />2 <br />454 <br />2 757 <br />1 0 <br />0 134 <br />0 363 <br />0000808 <br />0462111 <br />649195 <br />Test 3 <br />3 <br />168 <br />3 280 <br />1 0 <br />0 134 <br />0 305 <br />0000679 <br />0388380 <br />7 7244 <br />Avg <br />0 335 <br />0000746 <br />0426710 <br />7.066308 <br />Test Pit No. 2 <br />Test 1 <br />0 <br />8 8 <br />0 147 <br />1 0 <br />0 134 <br />6 818 <br />0015191 <br />8685582 <br />03454 <br />Test 2 <br />0 <br />205 <br />0 342 <br />1 0 <br />0 134 <br />2 927 <br />0006521 <br />3728445 <br />0804625 <br />Test 3 <br />0 <br />226 <br />0 377 <br />1 0 <br />0 134 <br />2 655 <br />0005915 <br />3381997 <br />088705 <br />Test 4 <br />0 <br />278 <br />0 463 <br />1 0 <br />0 134 <br />2 158 <br />0004809 <br />2749393 <br />1 09115 <br />Avg <br />2 580 <br />0005748 <br />3286611 <br />0927608 <br />Test Pit No. 3 <br />Test 1 <br />0 <br />220 <br />0 367 <br />1 0 <br />0 134 <br />2 727 <br />0006076 <br />3474233 <br />08635 <br />Test 2 <br />0 <br />22 5 <br />0 375 <br />1 0 <br />0 134 <br />2 667 <br />0005941 <br />3397028 <br />0883125 <br />Test 3 <br />0 <br />238 <br />0 397 <br />1 0 <br />0 134 <br />2 521 <br />0005617 <br />3211476 <br />093415 <br />Test 4 <br />0 <br />236 <br />0 393 <br />1 0 <br />0 134 <br />2 542 <br />0005664 <br />3238692 <br />09263 <br />Avg <br />I <br />1 <br />1 2 614 <br />0005825, <br />3330357 <br />1 0901769 <br />The results of the infiltration tests in the test pits indicate good to excellent infiltration properties of the <br />waste rock material with calculated required surface areas of 0.80 ft2 to7 ft' to accommodate infiltration <br />of a 3 gallon per minute discharge. The average for the area needed for a 3 gpm discharge for all of the <br />tests conducted is 2.5 ft . The proposed constructed infiltration trenches will be at least 30 ft. long by 4 <br />ft. wide, an area of 120 W. This is over 48 times the average calculated area needed, and based on the <br />average calculated flux, would accommodate infiltration of approximately 360 gpm. <br />On the basis of the above infiltration tests, it is improbable that the discharging mine water will result in <br />outfalls cascading off the lower bench or discharging from the slope below the lower bench and into <br />Dry Gulch. It is likely that the underlying native colluvium is of sufficient permeability to transmit the <br />infiltrating mine water to the underlying colluvial aquifer. If such an outfall was to develop, OOSI <br />would remedy the situation by scarifying the existing trenches to enhance infiltration, expanding the <br />size of the infiltration trenches, or relocating the infiltration trenches. Other actions would be taken to <br />prevent the occurrence of surface discharge that constitutes an outfall. <br />3. Please sped whether or not leaching of hazardous or toxic constituents from the waste rock will <br />occur. How does the operator propose to determine whether or not this will be an issue? In the case <br />that leaching does occur what will be done to address the issue? <br />Warsha11121713.doc <br />