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GENERAL46097
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GENERAL46097
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Last modified
8/24/2016 8:17:06 PM
Creation date
11/23/2007 2:20:28 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1980005
IBM Index Class Name
General Documents
Doc Date
12/6/2002
Doc Name
Proposed Decision & Findings of Compliance for RN4
Permit Index Doc Type
Findings
Media Type
D
Archive
No
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(1) Intemxption of the aquifer by physically removing the coal and its <br />overburden. Mining of the coal will interrupt the aquifer function upgradient <br />of Twentymile Pazk. This will reduce the recharge potential to the <br />down-gradient aquifer for a short period of time. <br />(2) After discreet mining areas have been backfilled, the spoils will resaturate. <br />A portion of the spoil water will rechazge the undisturbed Wadge Coa] and <br />overburden immediately down-gradient. This rechazge water will be high in <br />TDS and other constituents. The concentrations of these constituents will be <br />greater than that which existed in the Wadge Coal and overburden aquifer <br />prior to mining. <br />(3) It is thought that the Wadge overburden, through sub-crops and outcrops, <br />may recharge creeks within Twentymile Basin. This rechazge maybe <br />duectly affected by the addition of the poor quality spoil dischazge water <br />during base flow conditions, or indirectly by the addition of this water to <br />associated alluvial bodies. Rechazge to the surface system could potentially <br />be affected by the interruption of the aquifer due to removal by mining. <br />Furthermore, upon induect recharge by the spoil aquifer, a plume of poor <br />quality water could diminish the water quality of the surface water system <br />within Twentymile Pazk. <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 by mining activities. <br />During mining, surface-runoff frem the disturbed aeeas is contained in sediment <br />ponds prior to dischazging from the site. Historically, the sediment ponds at the <br />Seneca II Mine dischazge regularly throughout the yeaz to the associated drainages <br />(Grassy Creek, Bond Creek, Cow Camp Creek). These drainages, at vazious times <br />of the year, rechazge the associated alluviaUcolluvial aquifers with the sediment <br />pond dischazge. These sediment pond dischazges aze typically higher in dissolved <br />constituents than the naturally occurring runoff from the undisturbed site. As the <br />alluviaUcolluvial 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 in <br />contact with previously disturbed lands, TDS increase over baseline conditions is <br />observable. This is due to the addition of spoils water, which has been dischazged <br />from backfilled portions of the mine site, to the alluvial system. <br />This general trend can be seen in water quality analyses from alluvial wells in Grassy <br />Creek and Little Grassy Creek. The water in these alluvial systems is down-gradient <br />of spoils and are probably receiving a contribution from spoils water containing high <br />levels of dissolved solids. In general, water from these sites has shown an overall <br />28 <br />
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