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MEMORANDUM <br /> AdrianBrown <br /> 1. The pre-mining water level on the western edge of the diatreme appears to have been approximately <br /> constant at about 9,450±50 ft above mean sea level (amsl).These levels appear to be controlled by the <br /> lowest topographic elevation that occurs around the periphery of the diatreme, which are shown: <br /> a. Squaw Gulch....................................9,350 ft amsl <br /> b. Arequa Gulch (west tributary).....9,450 ft amsl <br /> c. Poverty Gulch.................................9,550 ft amsl <br /> d. Arequa Gulch (main branch)........9,600 ft amsl <br /> e. Grassy Valley..................................9,750 ft amsl <br /> Thus pre-mining infiltration occurring on at least the western portion of the top of the hill that formed <br /> the Cripple Creek mining district would have flowed through the diatreme generally west towards the <br /> lowest point of discharge, Squaw Gulch. <br /> 2. The pre-mining water levels in mines in the center of the diatreme were in the vicinity of 9,710± 10 ft <br /> amsl, approximately 250 feet higher than the water levels in the mines in the diatreme to the west, and <br /> approximately 40 feet lower than the lowest topographic elevation in Grassy Valley, at the edge of the <br /> diatreme(9,750 ft amsl).This finding indicates that in pre-mining time there was potential for flow to <br /> the west from what will become the eastern mining area, with (surface)discharge from the diatreme <br /> generally to the west. <br /> 3. There were two exceptions to the pre-mining water level in the center of the diatreme being 9,710± 10 <br /> ft amsl: <br /> a. Isabella Mine, which had a pre-mining water level of 9,543 ft amsl, 150 feet lower than the <br /> adjacent mines to the south.This unexpected result was reported by Lindgren and Ransome <br /> (1906),who confirmed it by reference to relatively deep oxidation levels (Plate 7). <br /> b. Victor Incline, which had a pre-mining water level of 9,613 ft amsl, 97 feet lower than the <br /> adjacent mines to the south (Lindgren and Ransome, 1906, p.234). <br /> One additional datapoint for water level in the diatreme is available close to the Grassy Valley overflow point at <br /> GVMW-24 (ABC, 2015).The water levels in southeastern Grassy Valley are elevated today,and would have been <br /> at least similarly elevated before mining. In particular,the water table at GVMW-24 is at elevation 9,780 ft amsl, <br /> some 30 feet higher than the Grassy Valley overflow point located approximately 2000 feet to the northeast. <br /> This well indicates that there is potential available for groundwater in the area east of GVMW-24 to up-well into <br /> Grassy Valley, and flow in the alluvium or on the surface down Grassy Valley towards Beaver Creek. Note that at <br /> this location,the water level is approximately 131 feet below ground surface(in Well GVMW-24A-250, <br /> completed 250 feet below ground surface), and the hydraulic conductivity at that level is 4x10.8 cm/sec,which <br /> greatly limits deep vertical seepage. Well GVMW-24B-100 is a shallower well at this location (100 feet deep), is <br /> dry, and has an (injection) hydraulic conductivity of 3.5x10-4 cm/sec, four orders of magnitude higher than the <br /> deeper well. This assemblage essentially prevents vertical flow, and infiltration from surface is diverted laterally, <br /> likely both to the west and to the east, as GVMW-24 is located in a groundwater"saddle" with heads reducing to <br /> both the east and the west,while increasing to both the north and the south.The low permeability at depth <br /> explains the high water table. It is unlikely that the water level and the water infiltration in this area have ever <br /> been affected by mine dewatering or the drainage tunnels.The elevated head at GVMW-24 demonstrates that <br /> Page 2 <br /> Adrian Brown Consultants, Inc. <br /> 130 W.4rh Ave., Denver CO 80223 <br /> 303-698-9080 www.abch2o.com <br />