# Relationship history for MSHA mine 3400454

Current hierarchy: **Petroleum Reserve Corp → Carbonex Coal Company → Porum Mine**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Sierra Coal Corp → Porum Mine; 1972-01-01 to 1975-03-24; source msha-controller-operator-history
- **controller_controls_mine:** Frank W  Podpechan → Porum Mine; 1972-01-01 to 1975-03-24; source msha-controller-operator-history
- **controller_controls_operator:** Frank W  Podpechan → Sierra Coal Corp; 1972-01-01 to 1975-03-24; source msha-controller-operator-history
- **operator_operates_mine:** Carbonex Coal Company → Porum Mine; 1975-03-25 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Petroleum Reserve Corp → Porum Mine; 1975-03-25 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Petroleum Reserve Corp → Carbonex Coal Company; 1975-03-25 to current/open; source msha-controller-operator-history