# Relationship history for MSHA mine 2901609

Current hierarchy: **Tucson Gas & Electric Co; Public Service Co of New Mexico → Western Coal Company → Western Coal Underground Test 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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **controller_controls_mine:** Tucson Gas & Electric Co  et al → Western Coal Underground Test Mine; 1973-11-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Western Coal Company → Western Coal Underground Test Mine; 1976-09-15 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Tucson Gas & Electric Co  et al → Western Coal Company; 1976-09-15 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Public Service Co of New Mexico et al → Western Coal Company; 1976-09-15 to current/open; source msha-controller-operator-history