Decision-Grade Risk and Cost Mapping for Illegal Gold Mining at Crucitas, Costa Rica: Prioritisation, Phased Remediation Portfolios, and Uncertainty-Aware Policy Ranking

Artisanal and illegal gold extraction in ecologically sensitive tropical landscapes can generate persistent environmental damage and public fiscal liabilities that accumulate even under formal mining prohibitions. Here we develop a decision-grade pipeline that converts observable environmental signals into (i) spatial prioritisation surfaces, (ii) phase-timed remediation portfolios, and (iii) present-value (PV) comparisons of legislative policy pathways under uncertainty, demonstrated for the Crucitas mining landscape (Cutris, northern Costa Rica). Five linked models are implemented. Remote-sensing change proxies are derived using consistent baseline (January 2019–December 2020) and recent (February 2024–January 2025) windows; multi-criteria indices then produce a 0–100 grid-cell prioritisation surface integrating land, water, and hydrologic dimensions. This prioritisation output is translated into a phased remediation portfolio across 1,324 costed grid cells, yielding a gross liability of US$548.0 million (10-year PV; 5% discount rate). PSA-related credits total US$167.3 million PV; enforcing a cell-level non-negativity floor yields a baseline net PV of US$408.0 million (simple gross-minus-credits would be US$380.8 million). Deterministic policy overlays produce policy-adjusted net PV of US$336.1 million under Exp. 24.717 (Δ = −US$71.9 million vs baseline; modeled royalty PV = US$93.8 million), US$418.6 million under Exp. 24.675 (Δ = +US$10.6 million), and US$421.7 million under Law No. 8904 (Δ = +US$13.7 million). Monte Carlo propagation yields a right-tailed baseline distribution (P10–P90 = US$385.4–519.1 million; P50 = US$450.1 million), with exceedance probabilities P(>US$400 million) = 0.8357 and P(>US$500 million) = 0.1786. Policy-adjusted uncertainty bounds indicate substantially reduced exceedance risk under Exp. 24.717 (P(>US$400 million) = 0.3833; P(>US$500 million) = 0.0179) and increased exceedance risk under non-mining pathways. Collectively, the results enable PV-consistent, uncertainty-aware ranking of contested pathways, with outcomes conditional on enforceable offsets, credible enforcement effectiveness, and residual-risk provisioning. The framework is transferable to other contested mining landscapes where phased interventions and policy alternatives require fiscally comparable evaluation.