# Relationship history for MSHA mine 1001702

Current hierarchy: **N A Degerstrom → N.A. Degerstrom → EV, Ballard & Blackfoot Bridge Mines**

- 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:** N A Degerstrom → EV, Ballard & Blackfoot Bridge Mines; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Dravo Corp & N A Degerstrom Inc → EV, Ballard & Blackfoot Bridge Mines; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Dravo-Soda Springs → EV, Ballard & Blackfoot Bridge Mines; 1985-09-01 to 2001-11-12; source msha-controller-operator-history
- **controller_controls_operator:** Dravo Corp & N A Degerstrom Inc → Dravo-Soda Springs; 1985-09-01 to 2001-11-12; source msha-controller-operator-history
- **operator_operates_mine:** Degerstrom Ventures → EV, Ballard & Blackfoot Bridge Mines; 2001-11-13 to 2014-01-22; source msha-controller-operator-history
- **controller_controls_mine:** Dravo Corp & N A Degerstrom Inc → EV, Ballard & Blackfoot Bridge Mines; 2001-11-13 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Dravo Corp & N A Degerstrom Inc → Degerstrom Ventures; 2001-11-13 to 2014-01-22; source msha-controller-operator-history
- **operator_operates_mine:** N.A. Degerstrom → EV, Ballard & Blackfoot Bridge Mines; 2014-01-23 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** N A Degerstrom → N.A. Degerstrom; 2014-01-23 to current/open; source msha-controller-operator-history