_INSPECTION - M1981302 ‎(17)‎

• Permit No: M1981302
• IBM Index Class Name: Inspection
• Doc Name: MINERALS PROGRAM INSPECTION REPORT
• Inspection Date: 4/13/1998
• Media Type: D
• Archive: No

'� 4 • (Page 2) • .
MINE ID # OR PROSPECTING ID # M-81-302
INSPECTION DATE 4-13-98 INSPECTOR'S INITIALS ACS
OBSERVATIONS
This inspection was conducted to make observations related to the Deepe Farm Pit perimeter
levee. Placement of fill to raise portions of the levee was approved by the Division of
Minerals and Geology (Division) through technical revision TR-006 to the Deepe Farm Pit
reclamation permit. The earthwork to install the approved levee raise was completed between
October 9 and October 16, 1997. A stipulation to the approval of TR-006 required the
operator to submit a construction report detailing how the earthwork specifications approved
in TR-006 were achieved and certifying that the levee raise was installed in accordance with
the approved design. The required construction report was submitted by the operator on
November 26, 1997.
The entire length of the Deepe Farm Pit perimeter levee was walked during this inspection;
the following observations were made:
1. Most of the creek side facing of the levee has been covered by sub-rounded boulders up
to an elevation one foot above the estimated water level that would result from a one percent
annual chance flood on South Boulder Creek.
2. The entire pit side outslope of the levee and those portions of the creek side of the
levee above the rock facing have been recently hydroseeded and hydromulched.
3 . At the location of test boring P-2 (CTL/Thompson Geotechnical Investigation dated
6/9/97) along the south part of the levee, the creek side levee outslope forms a convex
curve. This portion of the levee has been armored with a angular, durable, well graded
riprap. The operator reports that this riprap was obtained from the Andesite Quarry at
Lyons, Colorado (reclamation permit no. M-77-141) .
4. A fiber mesh reinforced concrete toe wall has been installed along the creek side of
the levee from approximately the location of the test boring P-2 around to the north to
approximately Station 105+00. This is a subgrade structure that is approximately four feet
deep and 12 inches wide.
5. The pit side and creek side levee outslopes were measured at nine locations that
appeared to be representative of the steepest slopes at the site. An Abney Level was used
to take these slope measurements. The steepest slope so measures was at 18.5 degrees. From
these measurements, it is concluded that the operator has achieved the permit standard of
maximum 3:1 outslopes for the levee.
6 . It was observed that at several locations seepage is emerging from the toe of the pit
side slope. The source of the seepage appears to be the Dry Creek Ditch No. 2 which flows
at the toe of the creek side slope, and was flowing at the time of this inspection. Review
of the test pit information and cross-sections included in the CTL/Thompson Geotechnical
Investigation dated 6/9/97, it would appear that the seepage flows from the irrigation ditch
into the gravel pit through native ground that is present beneath the levee fill. It is
noted that the Deepe Farm Pit gravel deposit is underlain by relatively impermeable shale
which would tend to force any leakage from the irrigation ditch to flow laterally at the
gravel/shale interface.
7. At most of the seepage locations discussed in item six above, the operator has installed