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GENERAL44735
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Last modified
8/24/2016 8:13:27 PM
Creation date
11/23/2007 1:16:13 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1992081
IBM Index Class Name
General Documents
Doc Date
5/29/1998
Doc Name
PROPOSED DECISION & FINDINGS OF COMPLIANCE FOR RN1
Permit Index Doc Type
FINDINGS
Media Type
D
Archive
No
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<br />Precipitation averages approximately 16 inches annually in the permit area and the <br />volume of runoff is limited. Most runoff comes from snow melt or intense thunderstorm <br />events. Flows in Dry Creek have ranged from 0 to 126 cfs (cubic feet per second) <br />upstream of the loadout to from 0 to 225 cfs downstream. Two sediment ponds handle <br />runoff at the loadout: the Truck Loop Pond usually discharges during spring snowmelt; <br />the Rail Loop Pond has razely dischazged. <br />Stream flow in Dry Creek generally increases downstream although some sections are <br />ephemeral. During the growing season diversions of water from Dry Creek above the <br />permit can significantly reduce and even periodically eliminate streamflow in the vicinity <br />of the loadout, while at the same time return flows from surrounding irrigated fields can <br />dischazge small volumes of water to Dry Creek below the loadout. <br />The dominant cations in Dry Creek water aze: magnesium, calcium and sodium; the <br />dominant anion is sulfate. The pH is generally azound 8.2. The concentration of the <br />major cations, total dissolved solids, and nitrate (possibly due to agricultural return flow) <br />increase during periods of low flow (baseflow). Total suspended solids (TSS), aluminum <br />and total iron increase during high flows. Average values for total dissolved solids (TDS) <br />are higher downstream than upstream of the loadout; with average values of 2,439 and <br />3,175 mg/1(milligrams per liter), respectively. <br />Please see Section B, Item III of this document for a discussion of the probable <br />hydrologic consequences (PHC) of the Loadout on surface water quantity and quality and <br />for a furtlter discussion of the surface water monitoring plan. Alluvia! valley floors <br />(AVF's) aze discussed in Section B, Item XIV of this document. <br />Ground Water vd ology <br />Ground water information is located in Tabs 7, 13, 14 and I5 of the permit application. <br />A surttmary.of this information can be found in Section B, Item III of this document, <br />along with specific findings related to ground water hydrology. <br />The coal storage and tipple azea of the HG Loadout is situated on alluvial and colluvial <br />materials overlying the Lewis shale. Waters from the Lewis shale aze primarily calcium <br />or sodium bicazbonate type although sulfate type water also occurs in the Lewis shale. <br />The source of sulfate is the reduction of sulfide minerals and organic materials in the <br />shales <br />The Lewis shale has low hydraulic conductivity (low permeability). It is generally <br />considzred to be an aquitard that re[ards transmission of surface water to the underlying <br />regional aquifer. thz Twentymile sandstonz. This low conductivity results in low well <br />yields which, along with poor water quality characteristics, precludes the use of Lewis <br />shale waters for use other than sock watering (Seneca II-W Permit Application, HGT[ <br />application Attachment 7-1). <br />
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