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 generates persistent environmental and fiscal liabilities that can accumulate even under formal mining prohibitions. This study develops a decision-grade pipeline that converts observable environmental signals into spatial prioritisation surfaces, phase-timed remediation portfolios, and 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 constructed using consistent baseline (January 2019–December 2020) and recent (February 2024–January 2025) windows; multi-criteria indices then yield a 0–100 grid-cell prioritisation surface integrating land, water, and hydrologic dimensions. The prioritisation output is translated into a phased remediation portfolio across 1,324 costed grid cells, producing a gross liability of US$548.0 million (10-year PV; 5% discount rate). PSA-related credits total US$167.3 million PV, reducing baseline net PV to US$380.8 million. Deterministic policy overlays yield policy-adjusted net PV of US$366.6 million under Exp. 24.717 (Δ = −US$14.2 million vs baseline; modeled royalty PV US$34.6 million), US$390.7 million under Exp. 24.675 (Δ = +US$9.94 million), and US$393.6 million under Law No. 8904 (Δ = +US$12.83 million). Monte Carlo propagation produces a right-tailed baseline distribution (P10–P90 = US$393.1–469.4 million; P50 = US$429.9 million) with exceedance probabilities P(>US$400 million) = 0.8522 and P(>US$500 million) = 0.0101. Policy-adjusted uncertainty bounds indicate reduced exceedance risk under Exp. 24.717 (P(>US$400 million) = 0.7024; P(>US$500 million) = 0.0031) and increased exceedance risk under non-mining pathways. Results support PV-consistent, uncertainty-aware comparison of contested pathways, with rankings conditional on enforceable offsets, credible enforcement, and residual-risk provisioning; the framework is transferable to contested mining landscapes where phased interventions and policy alternatives require fiscal comparability.