# Relationship history for MSHA mine 0404621

Current hierarchy: **Hanson PLC → South Coast Materials Company → NORTH TWIN OAKS VALLEY QUARRY**

- 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:** Koppers Company Inc → NORTH TWIN OAKS VALLEY QUARRY; 1950-01-01 to 1988-11-13; source msha-controller-operator-history
- **operator_operates_mine:** South Coast Asphalt Products Company → NORTH TWIN OAKS VALLEY QUARRY; 1982-12-01 to 1988-11-13; source msha-controller-operator-history
- **controller_controls_operator:** Koppers Company Inc → South Coast Asphalt Products Company; 1982-12-01 to 1988-11-13; source msha-controller-operator-history
- **operator_operates_mine:** South Coast Materials Company → NORTH TWIN OAKS VALLEY QUARRY; 1988-11-14 to 1991-12-15; source msha-controller-operator-history
- **controller_controls_mine:** Hanson PLC → NORTH TWIN OAKS VALLEY QUARRY; 1988-11-14 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hanson PLC → South Coast Materials Company; 1988-11-14 to 1991-12-15; source msha-controller-operator-history
- **operator_operates_mine:** Roy E Ladd Inc → NORTH TWIN OAKS VALLEY QUARRY; 1991-12-16 to 1995-06-30; source msha-controller-operator-history
- **controller_controls_mine:** Eric R  Ladd et al → NORTH TWIN OAKS VALLEY QUARRY; 1991-12-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Eric R  Ladd et al → Roy E Ladd Inc; 1991-12-16 to 1995-06-30; source msha-controller-operator-history
- **operator_operates_mine:** South Coast Materials Company → NORTH TWIN OAKS VALLEY QUARRY; 1995-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hanson PLC → South Coast Materials Company; 1995-07-01 to current/open; source msha-controller-operator-history