# Relationship history for MSHA mine 4606494

Current hierarchy: **Exxon Corp & Columbia Gas System Inc → Columbia Coal Gasification Corp → Glenhayes Site**

- 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:** Columbia Coal Gasification Corp → Glenhayes Site; 1982-03-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Exxon Corp & Columbia Gas System Inc → Glenhayes Site; 1982-03-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Exxon Corp & Columbia Gas System Inc → Columbia Coal Gasification Corp; 1982-03-01 to current/open; source msha-controller-operator-history