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The Wadge Coal and overburden units are aquifers which have potential for <br />local use. Well yields for the Wadge Coal and overburden have been reported <br />at between 2 and 5 gpm. In the vicinity of the Seneca II Mine site, both <br />units have been used for domestic and livestock purposes. <br />The Wadge Coal has been mined in the northern portion of the permit area <br />(Sand Wash Ground Water Basin) in the past. During previous permit terms, the <br />Wadge Coal was extracted from the southeastern portion of the permit area, <br />which is located within the Twentymile Park Basin. <br />The portion of Twentymile Park in which the Seneca II Mine is located has been <br />identified as a recharge area. As such, the potential impacts of mining will <br />be threefold: <br />(1) Interruption of the aquifer by physically removing the coal and its <br />overburden. Mining of the coal will interrupt the aquifer function <br />upgradient of Twentymile Park. This will reduce the recharge <br />potential to the down-gradient aquifer for a short period of time. <br />(2) After discreet mining areas have been backfilled, the spoils will <br />resaturate. A portion of the spoils water will recharge the <br />undisturbed Wadge Coal and overburden immediately down-gradient. <br />This recharge water will be high in TDS and other constituents. The <br />concentrations of these constituents will be greater than that which <br />existed in the Wadge Coal and overburden aquifer prior to mining. <br />(3) It is thought that the Wadge overburden, through sub-crops and <br />outcrops, may recharge creeks within Twentymile Basin. This <br />recharge may be directly affected by the addition of the poor <br />quality spoil discharge water during base flow conditions, or <br />indirectly by the addition of this water to associated alluvial <br />bodies. Recharge to the surface system could potentially be <br />affected by the interruption of the aquifer due to removal by <br />mining. Furthermore, upon indirect recharge by the spoils aquifer, <br />a plume of poor quality water could diminish the water quality of <br />the surface water system within Twentymile Park. <br />The alluvial aquifer system, which includes alluvial bodies in the Fish Creek <br />Drainage (including Bond and Cow Camp Creeks) and the Grassy Creek Drainage, <br />will be impacted due to mining activities. <br />During mining, surface runoff from the disturbed areas is contained in <br />sediment ponds prior to discharging from the site. Historically, the sediment <br />ponds at the Seneca II Mine discharge regularly throughout the year to the <br />associated drainages (Grassy Creek, Bond Creek, Cow Camp Creek). These <br />drainages, at various times of the year, recharge the associated <br />alluvial/colluvi al aquifers with the sediment pond discharge. These sediment <br />pond discharges are typically higher in dissolved constituents than the <br />naturally occurring runoff from the undisturbed site. As the <br />alluvial /colluvial water quality closely mirrors the quality of the stream, a <br />degradation (i.e, increase in TDS) is observable in alluvial monitoring wells <br />down-gradient of the mine site. In portions of Little Grassy Creek drainage <br />which are in contact with previously disturbed lands, an increase in TDS over <br />baseline conditions is observable. This is due to the addition of spoils <br />water, which has been discharged from backfilled portions of the mine site, to <br />the alluvial system. <br />-2 6- <br />