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REP40848
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REP40848
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Entry Properties
Last modified
8/25/2016 12:42:47 AM
Creation date
11/27/2007 8:51:39 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1981012
IBM Index Class Name
Report
Doc Date
4/5/1991
Doc Name
THE NEW ELK MINES WASTE PILE UNDERDRAIN DESIGN PN C-81-012
From
MLRD
To
BERHAN KEFFELEW
Permit Index Doc Type
STABILITY REPORT
Media Type
D
Archive
No
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iii iiiiiiiiiiiiiiii <br />999 <br />STATE OF COLORADO <br />MINED LAND RECLAMATION DIVISION of ~o~o <br />Department of Natural Resources ~~, ~' q9 <br />1313 Sherman 51., Roam 215 <br />Denver, CO 80203 • ~ ~..,7 <br />303 866-3567 '„~,' <br />FA x: 303 832-8106 <br />Roy Romer. <br />Governor <br />Fretl R. Banta, <br />DATE : Apr i 1 5 , 1991 ^_ Division Dvea°` <br />T0: Berhan Keffelew <br />h ROM: J im Pendl eton <br />RE: The New <br />Este Pile Underdrain Design <br />No: C-81-012) <br />In response to your recent request, I have reviewed the permit documents for <br />the New Elk Mine's coal refuse disposal structure. You have indicated the <br />receipt of a ten day letter from the OSMRE questioning the design of the <br />structure's underdrain. <br />The application design documents depict an 8' x 16' rods underdrain, as <br />required by the regulations in place at the time of its approval. Since that <br />time the OSMRE regulations have been modified, deleting the specified cross <br />section area. Figures 5 through 10 within the design document stability <br />analysis report depict the cross section and longitudinal profiles of the <br />approved underdrain system. <br />the New Elk underdrain is intended to serve primarily as an interceptor of <br />sub grade seepage and percolation through the pile's superstory. The <br />underdrain is designed to weep into the sediment pond located at the toe of <br />the refuse pile. I have visited the site at least annually since the pile's <br />corRnencement and have never observed flow from the underdrain. Surface runoff <br />from the pile does collect within the pond. <br />In ~ experience the 8' x 16' underdrain cross section is grossly oversized <br />for our semi-arid climatic conditions. The boiler plate requirement, like <br />many others inherited from the OSMRE regulations, refl ects experience in humid <br />climates in other portions of the USA. Practices such as head-of-hollow fill <br />construction with chimney drains necessitate large cross-sectional drains <br />capable of accommodating significant flows. In Colorado we have not <br />encountered situations reminiscent of these eastern and mid-continent design <br />situations. <br />In conducting mineral program mine plan reviews I have occasionally required <br />the applicant to complete detailed sub drain designs, considering flow <br />projections, drain siltation and cavitation potential, drain matrix mechanical <br />strength and abrasion characteristics, etc. Specifically, several large <br />proposed spent shale disposal piles were required to complete detailed design <br />procedures. Even in those situations, representing piles as large as <br />300 million cubic yards with depths of up to 1300' with chimney drains <br />
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