# Relationship history for MSHA mine 2901833

Current hierarchy: **Washington Group International Inc → Yampa Mining Company → De-Na-Zin**

- 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

- **controller_controls_mine:** Washington Group International Inc → De-Na-Zin; 1977-12-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Sunbelt Mining Company Inc → De-Na-Zin; 1980-08-01 to 1989-10-12; source msha-controller-operator-history
- **controller_controls_mine:** Public Service Co Of New Mexico → De-Na-Zin; 1980-08-01 to 1989-10-12; source msha-controller-operator-history
- **controller_controls_operator:** Public Service Co Of New Mexico → Sunbelt Mining Company Inc; 1980-08-01 to 1989-10-12; source msha-controller-operator-history
- **operator_operates_mine:** Yampa Mining Company → De-Na-Zin; 1989-10-13 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Washington Group International Inc → Yampa Mining Company; 1989-10-13 to current/open; source msha-controller-operator-history