# Relationship history for MSHA mine 2602649

Current hierarchy: **Kevin L  Robertson; Craig D  Holt → Sierra Nevada Construction Inc. → Portable Rock Plant #1**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **controller_controls_mine:** Craig D  Holt et al → Portable Rock Plant #1; 2006-09-27 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Sierra Nevada Construction Inc. → Portable Rock Plant #1; 2008-05-22 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Craig D  Holt et al → Sierra Nevada Construction Inc.; 2008-05-22 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Kevin L  Robertson et al → Sierra Nevada Construction Inc.; 2008-05-22 to current/open; source msha-controller-operator-history