# Relationship history for MSHA mine 2500510

Current hierarchy: **CRH PLC → Central Sand & Gravel Co → Pit #76 Norfolk**

- 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 → Pit #76 Norfolk; 1950-01-01 to 2018-06-20; source msha-controller-operator-history
- **operator_operates_mine:** Central Sand & Gravel Company → Pit #76 Norfolk; 1950-01-01 to 1989-04-05; source msha-controller-operator-history
- **controller_controls_mine:** Heimes Don → Pit #76 Norfolk; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Heimes Don → Central Sand & Gravel Company; 1950-01-01 to 1989-04-05; source msha-controller-operator-history
- **operator_operates_mine:** Central Sand & Gravel Co → Pit #76 Norfolk; 1989-04-06 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ash Grove Cement Company → Central Sand & Gravel Co; 1989-04-06 to 2018-06-20; source msha-controller-operator-history
- **controller_controls_mine:** CRH PLC → Pit #76 Norfolk; 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