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APPCOR12482
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APPCOR12482
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Entry Properties
Last modified
8/24/2016 6:32:54 PM
Creation date
11/19/2007 2:31:15 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1987072
IBM Index Class Name
Application Correspondence
Doc Date
5/11/1987
Doc Name
LA PLATA 1 MINE 2ND ADEQUACY LETTER FN C-87-072
From
MLRD
To
LA PLATA COAL CORP
Media Type
D
Archive
No
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Mr, Joe Carpio - 6 - May 11, 1987 <br />f. Page 2.05-19 states the coal loadout area is shown on Map 11. <br />g. Pages 2.05-48 and -49 states the water monitoring points are <br />shown on Map 7. <br />11. Page 2.05-23 states a NPDES permit was issued. Please submit this permit <br />for inclusion into Exhibit 3. <br />12. No design was submitted fora nonclogging dewatering device. A steel <br />plate or tripod of rods which projects in front of the spillway orifice <br />should be designed and submitted for review by the Division. Ultimately, <br />this device needs to be constructed to deflect floating debris away from <br />the pond outlet. <br />13. Cross-sections and stage-storage calculations were submitted; however, no <br />detention time calculations were provided for the existing sediment <br />pond. Based on the submitted information, the Division has calculated <br />the size of the dewater orifice required to provide the theoretical <br />detention time of 24 hours for the 10-year, 24-hour design storm runoff <br />volume. This will require a plate be welded over the end of the existing <br />24 inch CMP spillway with an opening of either a souare 2.6 inches per <br />side or a circle with a diameter of 3.0 inches located at the bottom of <br />the plate. The calculations and method are attached and should be <br />reviewed. If agreed upon, this information needs to be included into the <br />permit application and incorporated onto the CMP. <br />14. The statement is made in Exhibit 7 that calculations used to design the <br />culverts can be shown if requested. As the drainage system has been <br />revised, the Division requests these calculations be submitted. <br />15. The Division received a statement on May 1, 1987 that it is La Plata <br />Coal's intention to use the pond as a stock pond during and after <br />mining. As such, there are some additional considerations which need to <br />be addressed in the permit application before the Division can agree to <br />this request. Astable water surface is required to be maintained in the <br />pond. Because the pond has been observed not to be able to hold water, <br />sealing of the pond will be necessary. Sealing of the pond with <br />bentonite, however, has been previously discussed and so this does not <br />impose any additional requirement. Also, La Plata Coal needs to <br />demonstrate that water will be ponded year-round. <br />As the pond will function as a sedimentation device during mining <br />activities, it is inappropriate to consider its use simultaneously as a <br />stock pond due to water quality limitations. Enclosing of the pond with <br />a fence would allow grazing in the surrounding area if another source of <br />water is found to support this use. <br />The proposal to incorporate the pond as a permanent impoundment can be <br />approved if a commitment to the above measures are included. Prior to <br />conversion of the sediment pond into its post-mining use as a stock pond, <br />an application will need to be submitted to the State Engineer's Office <br />for approval of its use as a stock pond. Any modifications necessary to <br />meet this criteria (enclosed) can be made at that time. <br />
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