Interesting review prepared by Piteau for EMR -> 2022
"1 Only the draft technical memos (Appendices A to E) were issued to VGC for comment, not the main report as it is a summary of those memos and does not present new information."
I have read a lot of information regard the Heap Model and mine progression through time. Some of the operationl requirements listed where not even physically possible.
"The latest Forte deterministic modelling, on the other hand, predicted no infringements on
the DAS for the entire period modeled (to 12/31/2029), with the minimum Total Available
Storage predicted to remain above 290,000 m3 for all of 2021, and above 250,000 m3 for the life of mine. The stochastic modeling estimated the minimum storage during 2021 to be
240,170 m3 (1st percentile/lower “tail”) and thus the report concluded there was “no
probability of an infringement on the DAS during the summer of 2021.” The 2019 annual
water balance modeling update (Forte, 30 April 2020) deterministic forecast predicted no
infringement on the DAS, and for 2020 and 2021 the Total Available Storage would be
maintained above 290,000 m3 (Fig. 20). The stochastic model predicted a 3.4% chance of
infringing on the DAS for one week (Fig. 36). These predictions are consistent with those
from the earlier modeling performed by The Mines Group (Water Balance Modeling for the
Eagle Gold Mine Proposed Heap Leach Pad Facility, Final Design, 26 Jan 2018) which
found “There is essentially no risk of encroaching on the DAS during Phase 1, Phase 2, or
Phase 3.” That report goes on to say, “On average the month of May maintains the DAS of
about 203,000 m3 and the most common value is on the order of 210,000 m3…there are
circumstances that could occur which would encroach on the DAS and those circumstances
are expected to occur about 2.7% of the time.” So far, they have occurred 100% of the
time.
The predictions missing the infringements for the first three years of operations raises concerns about the reliability of the model forecasts." "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."
There are memo's at the end directed to EMR by Mark E. Smith, P.Eng. (YT) of Piteau Associates by that are interesting.
One thing for sure if the operatins manuals don't reflect reality then it's a situation just waiting for something to happen.
There are other questions that need to asked as to what the status of the recommendations where at the time of "loss of containment".
[url=https://emr-ftp.gov.yk.ca/emrweb/COMM/major-mines/eagle-gold/Eagle Gold Heap Leach Facility And Cyanide Management Review.pdf]https://emr-ftp.gov.yk.ca/emrweb/COMM/major-mines/eagle-gold/Eagle Gold Heap Leach Facility And Cyanide Management Review.pdf[/url]
https://emr-ftp.gov.yk.ca/emrweb/COMM/major-mines/eagle-gold/Eagle%20Gold%20Heap%20Leach%20Facility%20And%20Cyanide%20Management%20Review.pdf