# Relationship history for MSHA mine 3607972

Current hierarchy: **Heidelberg Materials AG → Hanson Aggregates Pma Inc → DREDGE ALLEGHENY II**

- 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:** F R G Industries Inc → DREDGE ALLEGHENY II; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Davison Sand & Gravel Company → DREDGE ALLEGHENY II; 1987-12-01 to 1989-01-15; source msha-controller-operator-history
- **controller_controls_operator:** F R G Industries Inc → Davison Sand & Gravel Company; 1987-12-01 to 1989-01-15; source msha-controller-operator-history
- **operator_operates_mine:** Pioneer Mid-Atlantic Inc → DREDGE ALLEGHENY II; 1989-01-16 to 2000-08-03; source msha-controller-operator-history
- **controller_controls_mine:** Pioneer International Ltd → DREDGE ALLEGHENY II; 1989-01-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Pioneer International Ltd → Pioneer Mid-Atlantic Inc; 1989-01-16 to 2000-08-03; source msha-controller-operator-history
- **operator_operates_mine:** Hanson Aggregates Pma Inc → DREDGE ALLEGHENY II; 2000-08-04 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Hanson PLC → DREDGE ALLEGHENY II; 2000-08-04 to 2007-08-22; source msha-controller-operator-history
- **controller_controls_operator:** Hanson PLC → Hanson Aggregates Pma Inc; 2000-08-04 to 2007-08-22; source msha-controller-operator-history
- **controller_controls_mine:** Heidelberg Materials AG → DREDGE ALLEGHENY II; 2007-08-23 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Heidelberg Materials AG → Hanson Aggregates Pma Inc; 2007-08-23 to current/open; source msha-controller-operator-history