Was there a disconnect between YTG, EMR & VGFirst I am not a mining expert but find the following interesting. The more I look at this there apears a lot of unanswered questions regards this report. If as it appears to be this was for the exclusive use of EMR (paid for by YTG)?
In the report is states:
"This report has been prepared
for the sole use of the Yukon Government."
After reading and scanning through the heap loading, monitoring and containment portions of the EAGLE GOLD HEAP LEACH FACILITY AND CYANIDE MANAGEMENT REVIEW by PITEAU ASSOCIATES dated July 2022 a few things stood out to me in regards the failure of the heap leach containment. Regards the reports recomendations was movement of containment increased as recommended?
Was this report made available to VG and recomendations implemented as per report.as there apears to be a lot of recomended actions and comments on montoring the actual leach pad containment (berm?). If this was implemented why did the prisms not work or was the collapse so sudden (hard to imagine considering safety factors) that the collaps just occured in a millisecond?
To me the above is the one that stands out (in regards the structural failure). Was there already concern when the report was requested after the containment structure and mine was operational. Did engineering pick up on the fact that perhaps movement was not being adequately monitored?
"6.2a: Add a network of survey prisms (with routine surveying and analysis of the
results) to the crest and downstream slopes of both the In-heap Pond and Events
Pond embankments.
6.2b: Specify the frequency of surveillance for instruments such as inclinometers
which cannot be automatically reported.
6.2c: Add a discussion about how critical instrumentation (such as piezometer) data
will be retrieved during an extended power outage.
6.2d: Where practical and consistent with shift rotations, group types of instruments
or monitoring measurements under the responsibility of the same person or group
of people/department"
Further
"6.2. Heap Leach Facility Surveillance and Response (Section 9)
Table 9.1-1 lists the surveillance method, frequency, and responsibility. The listed “Embankment
Geotechnical Instrumentation” includes only piezometers and a single inclinometer. Survey prisms
are one of the most common and most effective means of monitoring slopes, including
embankment dams, and can provide very early warning of problems. The table also sets the
frequency of monitoring of these instruments as “Continuous using wireless relays to the office.”
However, inclinometers (and generally prisms) require manual surveys and thus the frequency of
the surveys should be specified. Further, during an extended power failure (such as the 72-hr failure
scenario for the pumping system), the piezometer data cannot be transmitted by wireless relays
either, unless there are back-up batteries in place.
There are also some items in Table 9.1-1 which are not clear. Specifically:
• For the solution collection and recovery systems, weekly surveillance is specified. However, for
a valley fill heap leach facility the solution collection system is under the heap, reporting to the
bottom of the In-heap Pond which is also filled with ore;
• Leak detection and recovery system (LDRS) monitoring ports require daily surveillance. The
LDRS monitoring ports for the In-heap Pond are at the bottom of the pond, buried beneath ore,
and located between two geomembrane liners. For the Events Pond, it is below the pond
(which contains some water much of the time) and between two geomembrane liners. Thus, no
visual inspection is possible. Flow to the LDRS is monitored with totalizing flowmeters, and
fluid is removed by either level-actuated pumps (according to the OMS) or weekly by manually
operating the pumps (according to the Annual Inspection reports);
• Instrumentation is surveilled monthly and per manufacturer’s guidelines. Yet some
instrumentation (e.g., piezometers) cannot be visually or otherwise inspected and only the data
is applicable to verify their functionality, while other instrumentation has surveillance
frequencies specified differently than monthly (the inclinometer is monitored quarterly,
according to Section 9.2.4); and,
• The responsibilities as listed in Table 9.1-1, have the same type of measurements being taken
by the different personnel. For example, piezometer data for the heap embankment and In-
heap Pond are the responsibility of the Process General Foreman, while the heap leach pad
piezometers are the responsibility of the Environmental Superintendent. The skills required to
monitor, calibrate, and analyze such data, to maintain the equipment, and to quickly identify
anomalous results, are complicated; there is value in having the same person performing these
functions across areas."