Drill and blast performance was always hot topic in decades past at underground mines. Today it feels like it has gone out of fashion somewhat, with efficiency KPI’s becoming the focus, especially in BI circles. Are we forgetting just how impactful 1% of overbreak can be in an underground stoping mine? I get it… why chase 1% less overbreak when an improvement consultant has dangled promises of 10% efficiency gains in front of your face? I’ll save the discussion about these slated efficiency gains for another article, but lets really look at what 1% overbreak or underbreak means for a typical stoping operation in 2025. While very hard to define an “average size UG operation” we’ll use for simplicity’s sake one with a yearly revenue of $500M. It’s pretty obvious that for every 1% underbreak, $5M is potentially lost, assuming it is never recovered (sterilised). It’s not that simple of course, but lets leave it there as a bit of a yard stick. 10-15% underbreak would not be considered an uncommon result for an operation mining stopes in the 10kt-100kt range, so we are talking about a lot of lost opportunity here, considering everything has already been spent to access and break the dirt. Overbreak is far more complex to work out the cost of, though it can lead to far worse results than underbreak which has a more direct correlation to loss. For example, over breaking into ore of a comparable quality results a gain right? Well, maybe… Your average grade will be maintained in this instance, as long as you can restrict overbreak to the stope walls with ore contacts, a rarity. The flip side is overbreaking into waste, which can hit doubly hard. The old mantra of “Ore + Waste = More Ore” has some holes when we look at the costs associated. In a mine which is production constrained (constrained by fleet capacity) every tonne of waste overbreak you bring up displaces a tonne of ore. This waste tonne then incurs the cost of haulage, grinding, separation and then takes up space in your tailings dam. In addition, as overbreak starts to artificially increase the amount of tonnes removed from the stope, delays to the sequence start to incur, which can range from un-impactful right through to a real pain in the date! Finally, overbreak leads to larger spans (Hydraulic Radii), and in some cases stope failure. Rarely will this be without impact and in the worst cases, this can destroy the value of a mining front. What could this potential overbreak cost be? We lets say you are operating at a 20% (EBITDA) margin and your overbreak goes from a well controlled 10% to a slightly less controlled 15%. At 10% overbreak, your entire margin comes from the last 18% of the ore you mine. Once you add an additional 5% waste overbreak to this number and displace that metal from your year, margins drops disproportionately to 14.4%. This means you have effectively given up 27% of your free cashflow! Remember, total material mined for the year stays the same in this example, you have simply diluted the year's average grade by mining extra waste instead of panned ore. While this is a simplified example using the basic accounting skills of a mining engineer, it illustrates the point... I’m preaching to the choir here if you are a professional underground drill and blast engineer. The issue in 2025 is that less and less of us are. Instead, engineers take a faster track to a senior role, with great tools making up for lack of learnt expertise (a common theme in my articles). The blame in my opinion does not sit with them however. Engineers will take an interest in whatever the industry holds in high regard. Our senior leadership in the mining space sets the standard, not the engineer in the seat. If D&B KPI’s are rarely discussed, the team is under-resourced, the reward is comparatively low and there is a lack of great coaching, then it makes sense the role will be seen as a stepping onto “more important things”. I believe great D&B expertise is the foundation of every great planning engineer. Furthermore, having the D&B nous to solve stoping challenges and unlock opportunities in a mine schedule, will take a scheduler from good to great. Thankfully, drill and blast is a well understood art, and there are many amazing engineers out there who can coach our newer generation on the fundamentals. We just need tech services and mining managers/superintendents to set a higher standard and provide the resources to coach our newer generations. There are some fantastic companies and resources out there who do exactly this, and you can add Strategic Mine Planning Services to that list. If you would like help to elevate the game of your D&B team quickly and sustainably, please reach out. We love coaching our newer generation and seeing the fast results that come with it for the operations that invest in their people. FREE OFFER! If you would like me to walk you through a case study where average overbreak and underbreak were reduced by almost 5% each, message me and lets line up a chat. It'll cost you nothing and you might get some real value from it.