# Relationship history for MSHA mine 2500250

Current hierarchy: **CRH PLC → Central Sand & Gravel Co. → Portable #6 (Dredge)**

- 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 → Portable #6 (Dredge); 1950-01-01 to 2018-06-20; source msha-controller-operator-history
- **operator_operates_mine:** Hartford Sand & Gravel Company → Portable #6 (Dredge); 1950-01-01 to 1988-02-21; source msha-controller-operator-history
- **controller_controls_mine:** Don  Rogert → Portable #6 (Dredge); 1950-01-01 to 1988-02-21; source msha-controller-operator-history
- **controller_controls_operator:** Don  Rogert → Hartford Sand & Gravel Company; 1950-01-01 to 1988-02-21; source msha-controller-operator-history
- **operator_operates_mine:** Central Sand & Gravel Co. → Portable #6 (Dredge); 1988-02-22 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ash Grove Cement Company → Central Sand & Gravel Co.; 1988-02-22 to 2018-06-20; source msha-controller-operator-history
- **controller_controls_mine:** CRH PLC → Portable #6 (Dredge); 2018-06-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** CRH PLC → Central Sand & Gravel Co.; 2018-06-21 to current/open; source msha-controller-operator-history