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2008-12-02_GENERAL DOCUMENTS - C1981010
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2008-12-02_GENERAL DOCUMENTS - C1981010
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Last modified
8/24/2016 3:38:28 PM
Creation date
12/2/2008 1:42:34 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1981010
IBM Index Class Name
GENERAL DOCUMENTS
Doc Date
12/2/2008
Doc Name
Proposed Decision & Findings of Compliance for SL9
From
Phase II
Permit Index Doc Type
Findings
Email Name
JDM
Media Type
D
Archive
No
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cover must equal or exceed the cover standard 25% live herbaceous cover and up to 22% <br />litter (Permit page 4-105). <br />Results of vegetation sampling indicated that all bond release blocks exceed the live <br />herbaceous cover standards. Reclaimed block A, D&H RSC 03-04 indicated an allowable <br />cover of 56.3%, with litter cover of 14.2% and reclaimed block D&F RSAB 02-04 indicated <br />an allowable cover of 74.1 %, with litter cover of 13.5%. Neither of the bond release blocks <br />exceeded the allowable litter cover percentage. <br />Although vegetation species diversity is not a criteria for Phase II bond release, the Division <br />evaluates cover data at Phase II to ascertain if the reclamation is approaching the diversity <br />success criteria. TMI's species diversity standards for rangeland areas consist of: <br />1) At least five principle species including a minimum of four cool-season perennial <br />grasses and a minimum of one perennial forb shall be established. <br />2) Each principle species shall contribute no less than 3% relative cover. <br />3) No single species shall contribute in excess of 50% relative cover. <br />4) No four species in combination shall exceed 80% relative cover. <br />(Permit page 4-121 a) <br />Cover data show that both blocks would likely achieve the diversity standards. Both bond <br />release blocks reported approximately 2.6% or less relative cover due to noxious weeds. This <br />low relative cover value of noxious weed species attests to TMI's diligence in implementing <br />weed control measures. <br />Sedimentology <br />TMI's bond release application compares pre- and post-mining sediment yields by calculating <br />the expected sediment yields for both conditions. TMI used two different calculation <br />methods: the Universal Soil Loss Equation (USLE) and the computer program SEDCAD 4. <br />The USLE calculates the expected average annual soil loss per acre of land and the SEDCAD <br />4 calculates the expected settleable solids concentration in runoff from a precipitation event. <br />In the USLE comparison, only the "C" factor is varied between the pre-mining and the post- <br />mining calculations; all other variables are constant for pre- and post-mining. The pre-mining <br />calculation uses baseline vegetation cover values from the permit application (Table 2.3-13 and <br />Table 4.4-2). The postmining calculation uses vegetation cover data for the disturbed area <br />collected in 2008. A chief cause of soil loss is transport of solids in suspension; therefore, the <br />comparison indicates the untreated drainage, currently, does not yield more suspended solids <br />than prior to mining. For the bond release parcels in SL-09, TMI calculated a pre-mining <br />sediment yield rate of 2.05 tons per acre per year and a post-mining rate of 0.47 tons per acre per <br />year. The considerable difference between these two calculated rates indicates the post-mining <br />rate is significantly less than the pre-mining rate. This conclusion is only valid if TMI used <br />reasonable variables in the USLE calculations. The Division finds that the variables used in the <br />Trapper Mine Page 8 December 2, 2008 <br />Phase III Bond Release
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