# Relationship history for MSHA mine 0901022

Current hierarchy: **Lawson Robert → Lawson → CAMP CREEK SAND 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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **controller_controls_mine:** Blue Circle Industries Plc → CAMP CREEK SAND PLANT; 1987-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** H & H Sand & Gravel Inc → CAMP CREEK SAND PLANT; 1988-06-01 to 1992-11-30; source msha-controller-operator-history
- **controller_controls_mine:** Hammon Harold L → CAMP CREEK SAND PLANT; 1988-06-01 to 1992-11-30; source msha-controller-operator-history
- **controller_controls_operator:** Hammon Harold L → H & H Sand & Gravel Inc; 1988-06-01 to 1992-11-30; source msha-controller-operator-history
- **operator_operates_mine:** Blue Circle Aggregates Inc → CAMP CREEK SAND PLANT; 1992-12-01 to 1994-06-30; source msha-controller-operator-history
- **controller_controls_operator:** Blue Circle Industries Plc → Blue Circle Aggregates Inc; 1992-12-01 to 1994-06-30; source msha-controller-operator-history
- **operator_operates_mine:** Lawson → CAMP CREEK SAND PLANT; 1994-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Lawson Robert → CAMP CREEK SAND PLANT; 1994-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Lawson Robert → Lawson; 1994-07-01 to current/open; source msha-controller-operator-history