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• <br />u <br />vertical groundwater flow are typically one or two orders of magnitude <br />Lower than the average horizontal permeability. Permeability values <br />calculated from well testing should therefore be used with caution. <br />The estimates of vertical permeability under creek fracture zones were <br />based primarily on the observed inflows in the Sylvester Gulch return area. <br />The estimated value is calculated to be about 0.1 gpd/sq.ft. which is about <br />an order of magnitude lower than the highest values calculated from well <br />tests in the creek areas. The estimated vertical permeabilities and antic- <br />ipated inflows under creek areas may be further refined when Sylvester <br />Gulch and Lone Pine Gulch are undermined between 1986 and 1991 under the <br />proposed mine plan If mine inflows under these gulches indicate that the <br />projections are not valid then a revised mining strategy under Dry Fork of <br />Minnesota Creek and Lick Creek would be considered. The current plan calls <br />for minimal extraction through a protective corridor under both creeks, <br />until subsidence data is obtained. At that time, the mining plan will be <br />updated or revised utilizing the subsidence data. Observation and <br />documentation of ac[ual mine inflows is probably the best way of projecting <br />future mine inflows in this area. Additional well data will not yield good <br />estimates of vertical permeability. <br />(This answer is referred to in the answer to questions: V. B. 9; V. D. 1, <br />5, 8, 13, 29, and 30; 3/17/86 question ~1.) <br />9. "Page 2-534 is a chart of projected mine inflows. This chart should be <br />calculated for the life of mine. Also, inflows from faults should be <br />calculated and included." <br />Observations in the Mt Gunnison mine during the past four years indicate <br />that groundwater inflows are very low and are seasonal in nature. Inflows <br />mainly occur in three situations: <br />1) In areas not close to major fracture zones where the overburden <br />cover is less than 300 feet. <br />This situation is typified by inflows observed near the main portal <br />entrance. Inflows are highly seasonal in nature and only tend to <br />occur for a few months following the onset of Spring snowmelt. <br />Maximum flows of 20-25 gpm may occur during the Spring but these <br />reduce to almost zero by the Summer. The inflows are believed to <br />represent the interception of groundwater in shallow bedrock and <br />colluvial zones that are only saturated during the Spring runoff <br />period. <br />2) In the vicinity of major fracture zones where the overburden cover <br />is less than 500 feet. <br />• <br />This situation is typified by inflows observed at the Sylvester <br />Gulch return area. Inflows are seasonal, reaching maximum rates of <br />about 30 gpm during the Spring and reducing to about 13 gpm during <br />the rest of the year. The more consistent nature of the inflows are <br />believed to be related to the proximity of more active bedrock <br />groundwater flow within major fracture zones. The fracture zones <br />appear to control the alignment of the major creeks in the area and <br />consequently are thought to be coincident with these creeks. The <br />V-17 <br />