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2009-09-14_REVISION - C1981019
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2009-09-14_REVISION - C1981019
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Last modified
8/24/2016 3:55:25 PM
Creation date
9/16/2009 1:33:03 PM
Metadata
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Template:
DRMS Permit Index
Permit No
C1981019
IBM Index Class Name
Revision
Doc Date
9/14/2009
Doc Name
Proposed Decision & Findings of Compliance
From
DRMS
To
Colowyo Coal Company
Type & Sequence
RN5
Email Name
JRS
Media Type
D
Archive
No
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diverted around the disturbance and waters from the disturbance itself are treated in sediment <br />ponds and must meet CDPS standards before being released. <br />Waters leaching salts from reclaimed spoils may eventually reach Taylor, Wilson and <br />Goodspring Creeks. It is believed that these spoil waters will still meet CDPS standards and will <br />not contribute salts in levels that would warrant changes in mining and reclamation plans. This <br />situation will be monitored through alluvial wells located on Wilson Creek (near the Gossard <br />Loadout) and on Good Spring Creek and West Fork Good Spring Creek, both above and below <br />mining disturbances. <br />A particular concern raised by the Division during the PR-02 review, was the potential that high <br />salinity spoil water discharged from proposed South Taylor pit backfill areas into the West Fork <br />of Good Spring Creek, would increase salinity levels on the main stem of Good Spring Creek, <br />potentially causing material damage by significantly reducing forage production on irrigated <br />fields on the Good Spring Creek alluvial valley floor. The potential for material damage was <br />assessed by the Division, based, on salt loading projections incorporating anticipated spoil <br />discharge quantity, worst case projected spoil discharge salinity, and historic low flow discharge <br />and salinity of Good Spring Creek, in selected upper and lower segments (see Section <br />2.05.6(3)(b)(iii) of permit Volume 12, and particularly Potential Surface Water Quality Impacts <br />discussion on page R2-118). The projected worst case salinity for Good Spring Creek <br />downstream of the West Fork confluence and upstream of Streeter Drainage confluence is 1192 <br />mg/1 TDS (1.86 mmhos/cm conductivity). Projected worst case for lower Good Spring Creek, <br />downstream of Streeter Drainage confluence is 1261 mg/1 TDS (1.97 mmhos/cm conductivity). <br />The Division inserted the projected worst case salinity values from the referenced permit section <br />for upper and lower reaches of Good Spring Creek into a material damage assessment formula <br />listed in the Division's January 1988 material damage guideline document (A Description of the <br />Material Damage Assessment Process Pertaining To Alluvial Valley Floors, Surface Water, <br />Ground Water And Subsidence At Coal Mines). Based on available data for moderately <br />sensitive species representative of the most sensitive forage species grown on the alluvial valley <br />floor fields, projected yield declines range from 2.1% to 2.4% for upper Good Spring Creek, and <br />from 1.1% to 1.3% for lower Good Spring Creek. The guideline document "suspect level" for <br />initial determination of potential material damage is a 3% decline in productivity for an alluvial <br />valley floor agricultural parcel. Based on this analysis, the Division has determined that the <br />proposed operation will not result in material damage to the Good Spring Creek alluvial valley <br />floor. Monitoring of spoil springs, alluvial aquifers on the West Fork and main stem of Good <br />Spring Creek, and surface water in the West Fork and main stem will be conducted to verify that <br />worst case salt loading projections are not exceeded. <br />Details of Colowyo's water monitoring plan are found in Section B, Item III of this document <br />and in Section 4.05 of the Permit. <br />D. Specific Findings Required by Rule 4.24 <br />Proposed Decision and Findings of Compliance 14 September 2009 <br />Permit Renewal 05 Page 72
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