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associated alluvial bodies. Recharge to the surface system could <br />potentially be affected by the interruption of the aquifer due to removal by <br />mining. Furthermore, upon indirect recharge by the spoil aquifer, a plume <br />of poor quality water could diminish the water quality of the surface water <br />system within Twentymile Park. <br />The alluvial aquifer system in the Fish Creek Drainage (including Bond and Cow <br />Camp Creeks) will be impacted by mining activities. <br />During mining, surface runoff from the disturbed areas is contained in sediment <br />ponds prior to discharging from the site. Historically, Pond 008 at the Seneca II <br />Mine discharges regularly throughout the year to Bond Creek. These drainages, <br />at various times of the year, recharge the associated alluvial/colluvial aquifers with <br />the sediment pond discharge. These sediment pond discharges are typically higher <br />in dissolved constituents than the naturally occurring runoff from the undisturbed <br />site. As the alluvial/colluvial water quality closely mirrors the quality of the <br />stream, a degradation (i.e. increase in TDS) is observable in alluvial monitoring <br />wells down-gradient of the mine site. <br />Wells in the alluvium of Bond Creek show that high-TDS water from mining <br />activity has not yet migrated very far beneath the creekbed. Water from the well <br />in Bond Creek has not shown TDS levels elevated much beyond their historic <br />values, near 5000 mg/1. <br />When Seneca Coal Company can demonstrate that the reclaimed lands meet the <br />Phase II bond release criteria, it is assumed that the majority of baseflow to Cow <br />Bond Creek will be contributed by spoil aquifer discharges to the surface system. <br />In the Bond Creek drainage, Wadge spoils aquifer discharges will contribute flow <br />to these tributary creeks and eventually to Fish Creek. During the months of June <br />and July, Bond Creek sustains flow its entire length to Fish Creek. During this <br />period, the creek contributes water to the associated alluvial aquifer. The spoils <br />spring discharges are sufficiently diluted by snowmelt runoff to preclude <br />degradation to the quality of the alluvial aquifers in the drainage. (See the Surface <br />Water section of this Probable Hydrologic Consequences statement for further <br />discussion regarding surface water impacts.) <br />Information supplied by Seneca Coal Company indicates that at its confluence with <br />Fish Creek, Bond Creek does not support flow during the months of August and <br />September. It is assumed that during this period of time, Bond Creek flows for <br />about 2 miles beyond the disturbed area boundary before becoming ephemeral. At <br />the point where the stream becomes ephemeral, it is assumed, for purposes of this <br />discussion, that the flow in the drainage is 0.2 cfs with a TDS concentration of <br />2,500 mg/l. <br />20