1999-02-24_INSPECTION - M1981302

• Permit No: M1981302
• IBM Index Class Name: Inspection
• Doc Date: 2/24/1999
• Doc Name: MINERALS PROGRAM INSPECTION REPORT
• Inspection Date: 2/18/1999
• Media Type: D
• Archive: No

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MINE ID # OR PROSPECTING ID # M-81-302
INSPECTION DATE 2/18/99 INSPECTOR'S INITIALS ACS
of this report.
The remainder of this report addresses the list of NLH concerns in order. The concerns are restated
in italic letters.
1. Criteria for construction of the berm. The criteria for the construction of the berm include
provision of adequate freeboard above the water surface elevation that would occur during the 100-
year flood, stability against erosion by the stream velocities that would result during a 100-year
flood, prevention of uncontrolled seepage through or under the berm, prevention of significant
settlement and cracking, and provision of adequate interior drainage. These criteria are outlined
in a letter to Western Mobile from DMG dated 5/26/97 constituting the adequacy review for the
technical revision TR-06 application to the Deepe Farm Pit Permit.
2. Was the berm constructed according to regulations? The Deepe Farm Pit perimeter levee was
constructed prior to issuance of the gravel pit reclamation permit (M-81-302). When improvements
to the berm were proposed in 1997, the DMG required a geotechnical evaluation of the existing berm
and a design report describing the technical aspects of the berm improvements. These items were
addressed in the "Geotechnical Investigation, Levee at Deepe Farm Pit,"~a report prepared by
CTL/Thompson submitted to the DMG on 7/18/97. An addendum to the CTL/Thompson report was submitted
to DMG on 8/12/97 to address some issues raised by DMG relative to the shear strength values used
as input to certain slope stability analyses. The DMG further required the submittal of a
construction report and certification that the levee improvements were completed in accordance with
the approved design plan. Such a report was prepared by CTL/Thompson and submitted to the DMG on
11/26/97. Based on these investigations, reports, and certifications, and observations made during
the DMG's 4/13/98 inspection, the finding has been made that the levee improvements were completed
in accordance with DMG regulations. The remaining tasks are to complete a piping analysis as
discussed above and to establish an adequate stand of vegetation on the levee and elsewhere in the
pit. Revegetation will be discussed in an inspection report to be filed by Greg Squire of the DMG.
3. State performance standards for the berm. State performance standards for the berm are found in
34-32-116 (7)(bl, C.R.S. which states:
Earth dams shall be constructed, if necessary to impound water, if the formation
of such impoundments will not interfere with mining operations, damage adjoining
property, or conflict with water pollution laws, rules or regulations of the
federal government or the state of Colorado, or any local government pollution
ordinances.
and in 39-32-116(7)(9), C.R.S. which states:
Disturbances to the prevailing hydrologic balance of the affected land and the
surrounding area and to the quality and quantity of wafer in surface and ground
water systems both during and after the mining operation and during reclamation
shall be minimized.
In order to assure that these performance standards would be met, the DMG first made the finding,
based on the floodplain studies that have been conducted on South Boulder Creek, that damage from
the 100-year flood without the levee would be greater than with the levee, all other factors being
equal. The DMG then required investigations, reports, and certifications, as discussed in item 2
above, to demonstrate that the levee would divert the 100-year flood. Finally, the DMG required
that the opera[or initiate an inspection and maintenance plan for the levee that will continue as
long as the reclamation permit is in force.
4. Particulars of slope, freeboard, seepage, and levee fill. The approved maximum inslopes and
outslopes for the berm are 3:1. It was determined during the 4/13/98 DMG site inspection that this
criteria had been met. See the attached inspection report. The crest elevations for the berm are
established through the DMG approval of technical revision TR-06. The DMG required submittal of
a profile of the crest elevation of the completed levee as established by a field survey. Such a
profile was prepared by Scott, Cox, and Associates, Inc. surveyors and was submitted to the DMG on