2008-09-29_PERMIT FILE - C1981019A (6)

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RULE 2 PERMITS Surface Water Ouali General Area Surface water quantity in the general area is variable and inconsistent from drainage to drainage. Drainages in the general area have not received the attention that the drainages adjacent to and within the permit area have received because there is no hydrologic connection between these areas. Flow estimates and water balance calculations for these areas have not been examined because they will not be disturbed by the Colowyo Mine. Permit Area The drainages that have been the most intensively studied in and adjacent to the mine area include Taylor Creek, Goodspring Creek and Wilson Creek. Continuous flow recorders have been maintained on Taylor Creek and Wilson Creek by the USGS since 1974. A continuous recorder was operated on Goodspring Creek from 1974 to 1978. The flow information resulting from these gages is presented in Table 2.04.7-8. These data reflect the highly variable nature of surface flows in the drainages. Taylor Creek, the intermittent stream, had mean monthly flows of 0.0 cubic feet per second (cfs) for much of the period of record. Mean flows greater than 0.0 cfs were extremely low and reached a peak of 2.80 cfs in May 1980 reflecting the high snowmelt generated runoff. The maximum and minimum monthly flows also included for Taylor Creek give a further insight into its dependence on snowmelt and rainstorm runoff. This information supports the contention of very limited groundwater seepage to sustain flows near the mining area. The maximum daily flow value of 18.00 cfs in February, 1980 was a result of high snowmelt runoff and rainfall on a melting snowpack. Minimum flows of 0.0 cfs again reflect the highly sporadic nature and intermittency of this stream. Wilson Creek, a perennial stream, also shows the dependency on runoff related events for large volumes of water. Mean monthly flows exhibit more consistency throughout the dry months as evidenced by a constant base flow ranging from 0.25 to 0.34 cfs in 1978, an extremely dry year. Wet year conditions in 1980 resulted in mean flows about three to four times higher than the dry year condition. However, low flows in late summer and early fall still range around 1.0 cfs; a limited water supply is indicated. During the spring runoff of 1984, several drainages experienced high levels of erosion. See the 1984 Annual Report for additional information of the impacts to Wilson Creek from high runoff that year. Maximum and minimum flow values on Wilson Creek exhibit less flashiness than Taylor Creek, but still show the highly runoff related response of this drainage to snowmelt and rainstorms. The highest flow recorded for Wilson Creek during the period was 43.0 cfs in May, 1979. May of 1980 had a recorded value of 41.0 cfs reflecting high precipitation and possibly some snowmelt contribution. Late summer and early fall maximums and minimums reflect little precipitation and a very low base flow probably contributed by bank storage and the minimal groundwater in the area. Goodspring Creek, designated as an Alluvial Valley Floor area (although located in an upland area and containing colluvial deposits), has similar characteristics to Wilson Creek. Mean monthly flow values are generally lower and sustained dry year base flows are less than 0.1 cfs. Waterflow in the valley floor is restricted by plant evapotranspiration and movement through the valley deposits. Therefore flow values, themselves, may be misleading. Maximum and minimum flow values are also substantially less flashy than Taylor Creek. Maximum values are not as high as Wilson Creek and this is also due to the evapotranspiration of plants and the infiltration of water into the valley deposits prior to channel interception. Minimum base flows are extremely low, much lower than for Wilson Creek, and ranged around 0.01 to 0.06 cfs in late summer and early fall of 1977. Rule 2 Permits 2.04.7-17 Revision Date: 6/23/08 Revision No.: MR-91