2015-12-21_REPORT - C1981019

• Permit No: C1981019
• IBM Index Class Name: Report
• Doc Date: 12/21/2015
• Doc Name: 4th Quarter 2015 Fill Monitoring Certification
• From: Tri-State Generation and Transmission Association, Inc
• To: DRMS
• Permit Index Doc Type: Waste Pile/Fill Report
• Email Name: ZTT
• Email Name: JRS
• Media Type: D
• Archive: No

West Pit Fill Inspection Certification
On December 09, 2015, 1 inspected the area in which the West
constructed. The purpose of this inspection was to observe the surface
3H:1 V Excess Fill Slope, inspect the areas dumped to final grade, insp
fill surface, inspect the fill for areas of water seepage or surface drainE
slopes, and satisfy the requirements of CDRMS Rule 4.09.1(1)(c) and F
of inspection, weather conditions were 42°F and Cloudy.
Based upon my observations, the regraded fill was observed to be
underdrain below the West Pit Fill was not seeping at the time of i
slumps or signs of significant erosion were noted on the fill surface.
Excess Spoil Fill was
k drain that borders the
the revegetation on the
inspect the final grade
4.09.1(11). At the time
and unchanged. The
:)n. No other seeps,
The current water level of the monitoring piezometer was obtained. Th water level taken at the
time of inspection was 82.5 feet from the ground surface, an increase in ater elevation of 1.2 feet
from the previous quarterly inspection.
reviewed the monument survey data collected on December 10, 2015. This data was compared
to the survey data collected during the previous quarter on September 28, 2015. After review of the
December 10, 2015 data, the largest indicated vertical displacement from the previous quarter
survey was 0.018 feet at the 7150 East Prism. The remaining prisms measured a displacement of
0.016 feet to -0.093 ft.
The 7250 West monument prism was missing during the fourth quarter,
during the first quarter of 2015. The 7250 West monument prism indicate
during this quarter; however the indicated movement is reversed (neg
previous movement trend. In my opinion, this indicated movement is not i
but rather related to the prism replacement. I observed no evidence of s
of inspection. The 7250 West area will be monitored closely.
Based on the remaining prism data, the displacement of the monumer
regard to the stability of the fill. The degree of measured displacement
settlement, survey variation, and monument disturbance from animal i
inspection, I observed no evidence of structural weakness, slumps,
conditions associated with this fill. The monument survey data is availat
at the Colowyo Mine site.
2014, and was replaced
the largest displacement
ve movement) from the
ated to slope movement,
>e movement at the time
are not of concern with
in be caused by normal
fic, weather etc. During
;ps or other hazardous
for review upon request
I am a Registered Professional Engineer in the State of Colorado. Being familiar with the Colowyo
operation, and relying on the information provided to me by Colowyo Personnel, the West Pit
Excess Spoil Fill is observed to be stable, at the time of inspection, and ir compliance with CDRMS
Rule 4.09.1(1)(c) and Rule 4.09.1(11) , and Permit C-1981-019.
163
f.
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