Operational and Capital Cost Comparison: Marimaca Copper Project (Feasibility Study) v. WOODY Benchmarks
Independent cost benchmarking is one of the most effective tools available to mining developers and investors for pressure-testing project economics. When a company’s internal estimates are measured against a bottom-up, data-driven model like WOODY, the gaps and the reasons behind them tell an important story about how costs are being framed and what risks may be understated.
The Marimaca Copper Project in Chile’s Antofagasta Region offers a compelling case study. Using inputs from Marimaca’s 2025 Feasibility Study (FS), WOODY produced its own independent estimates for both operating and capital costs, revealing a significant divergence on the operating side and closer alignment on capital once scope differences were accounted for.
Operating Costs: A Meaningful Gap
WOODY estimated total operating costs of US$18.35/ore tonne against Marimaca’s reported US$11.86/ore tonne, a difference of US$6.49/ore tonne or roughly 55%. This is a substantial gap and one worth unpacking.
Marimaca’s Feasibility Study lists operating costs by standard categories, such as mining, crushing, agglomeration, leaching, SX/EW, etc., which is a common approach in technical reports but can obscure the full cost burden of running a mine. WOODY builds its estimates from the ground up using equipment-based cost drivers, capturing supplies, hourly and salaried labor, equipment operation, and overhead in a way that tends to surface indirect costs that process-area reporting can underweight. For a project like Marimaca operating in a remote, arid environment with significant water and power infrastructure requirements, these indirect costs can be material.
Capital Costs: Closer Than They Appear
At first glance, WOODY’s capital estimate of US$978M looks considerably lower than Marimaca’s reported US$1,240M. However, the comparison requires an important adjustment. Marimaca’s Feasibility Study includes US$195M in off-site infrastructure that falls outside WOODY’s scoping methodology, specifically the Seawater Supply Delivery Pipeline (US$139M, inclusive of a Reverse Osmosis Plant), the High Voltage Power Line (US$54M), and port-related Infrastructure, Buildings & Roads (US$2M, covering transport and storage/shipping of processed copper to Mejillones).
Stripping those out brings Marimaca’s comparable capital figure to US$1,045M, narrowing the gap to approximately US$67M or about 6%. That level of variance is well within the range of normal differences in contingency treatment, construction management allowances, and indirect cost assumptions between a company estimate and an independent model.
What This Means for Investors
The operating cost divergence is the more significant finding here. A US$6.49/ore tonne gap sustained over a multi-decade mine life has meaningful implications for project-level returns and net present value. Whether Marimaca’s estimate holds will depend heavily on how Chilean labor markets, reagent costs, and energy prices evolve, all inputs that WOODY tracks and updates continuously.
The capital cost picture, once scoped consistently, is broadly reassuring. However, investors should keep a close eye on whether off-site infrastructure costs, particularly water supply in one of the driest regions on earth, stay within the feasibility estimates as the project advances.
Benchmarking with WOODY
WOODY provides a consistent, independently derived framework for evaluating project economics, one that doesn’t rely on a developer’s assumptions about their own costs. For assets like Marimaca, where operating environment and infrastructure complexity can drive wide ranges in outcomes, benchmarking against WOODY gives investors and developers an important second opinion before capital is committed.
Learn more about WOODY here: WOODY | Costmine Intelligence
