Recon #12 of 17. Counting Trucks or Why Dispatch Numbers are Important

Hi everyone and thanks for your interest in mining geology!

When it comes to truck counts and dispatch numbers, this process often garners less attention from reconciliation geologists compared to more scientifically inclined tasks, such as estimating parameters in the grade control model or adjusting for post-blast movement. This tendency is understandable because dispatch information typically isn't directly utilized in official reporting tables. Usually, mined tonnages are adjusted using survey data, and reconciled grades are derived from mill outputs. The exception is the use of dispatch data to determine stockpile grades based on polygon proportions. Nevertheless, ensuring accuracy in these numbers holds significant value. Therefore, let's complete the production geology aspect of the reconciliation process by discussing best practices for truck counting and how it can add an extra dimension to our ore control toolbox.

In most open pits nowadays, trucks and loading equipment come equipped with GPS control systems. These systems not only enable tracking the machines' locations but also facilitate determining the location of the material being taken. I've heard that some software even permits uploading blasted block models, though typically we still operate with polygons, preferably post-blasted, in 2D. The degree of control dispatchers have over the process varies, often depending on the skill level of the loader operators, ranging from manual switches to automatic ore type assignments based on the GPS location of the digging point.

Irrespective of other factors, the number one priority for ore control should be ensuring the effective utilization of GPS, maintaining communication equipment availability at high 90s, and providing appropriate training for operators and dispatch personnel. If any of these elements are lacking, it can lead to massive misclassification in the pit, at the very last stage of geology data conversion. It's disheartening to see good ore control practices get sunk only because material isn't being extracted from the intended location. Practices such as digging to the line, ore spotters logging trucks, and reconciling with dispatch once per shift, along with regular visits by production geologists, can improve results, especially in cases of complex polygon geometries. However, the primary responsibility lies with the automatic material selection systems integrated into modern GPS software, which should handle the bulk of the workload.

A solid daily control practice that's easily established and upheld is maintaining an updated list of active polygons, predicted balances, and mined-out balances, revising it at least twice daily. Sometimes, with just a few queries, you can keep this summary up-to-date in real-time. This approach assists production geologists in continuously monitoring the mining process and proactively addressing over- or under-mining issues. While it may not always resolve misclassification problems (as a polygon could be misclassified without being overmined), it serves as a straightforward and robust sanity check for your daily material balance. Simple thing but often overlooked.

The global end-of-the-month compiled numbers of Dispatch/Post-Blast Polygons hardly reveal any insights unless there's a major screw-up in mining quality control processes. The grades should be identical (which isn't surprising since the same data source is used), while tonnage discrepancies might offset each other, even in cases of gross misclassification. However, breaking down the month's results on a polygon-by-polygon basis yields significantly more insights. If you're not already plotting tonnes predicted vs mined, it's high time to start for peace of mind. Typically, the lower the correlation, the worse your F2 grade recon, as it's unlikely you'll blend the high-grade perimeter with an even higher-grade one ??

Those quick tips and tricks sum up the ore control process all the way to the mill; there's not much else we can do on the mining end. In the next posts, we'll delve into the dark arts of mill grade reconciliation and first discuss the additional metrics we can use to enhance our F2.

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