# Relationship history for MSHA mine 3502970

Current hierarchy: **CRH PLC → Ash Grove Cement Co → Durkee Cement Plant**

- 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:** Ash Grove Cement Company → Durkee Cement Plant; 1950-01-01 to 2018-06-20; source msha-controller-operator-history
- **controller_controls_mine:** Oregon Portland Cement Company → Durkee Cement Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Oregon Portland Cement Company → Durkee Cement Plant; 1979-12-01 to 1983-12-18; source msha-controller-operator-history
- **controller_controls_operator:** Oregon Portland Cement Company → Oregon Portland Cement Company; 1979-12-01 to 1983-12-18; source msha-controller-operator-history
- **operator_operates_mine:** Ash Grove Cement Co → Durkee Cement Plant; 1983-12-19 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ash Grove Cement Company → Ash Grove Cement Co; 1983-12-19 to 2018-06-20; source msha-controller-operator-history
- **controller_controls_mine:** CRH PLC → Durkee Cement Plant; 2018-06-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** CRH PLC → Ash Grove Cement Co; 2018-06-21 to current/open; source msha-controller-operator-history