# Relationship history for MSHA mine 1800341

Current hierarchy: **Aggregate Management, Inc → Laurel Sand & Gravel INC. → Laurel Hill 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: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Lehigh Portland Cement Company → Laurel Hill Quarry; 1950-01-01 to 2002-01-31; source msha-controller-operator-history
- **controller_controls_mine:** Heidelberg Materials AG → Laurel Hill Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Heidelberg Materials AG → Lehigh Portland Cement Company; 1950-01-01 to 2002-01-31; source msha-controller-operator-history
- **controller_controls_mine:** Aggregate Management, Inc → Laurel Hill Quarry; 1983-04-07 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Heidelberg Materials AG → Laurel Hill Quarry; 2000-07-21 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Lehigh Cement Company → Laurel Hill Quarry; 2002-02-01 to 2020-08-09; source msha-controller-operator-history
- **controller_controls_operator:** Heidelberg Materials AG → Lehigh Cement Company; 2002-02-01 to 2020-08-09; source msha-controller-operator-history
- **operator_operates_mine:** Laurel Sand & Gravel INC. → Laurel Hill Quarry; 2020-08-10 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Aggregate Management, Inc → Laurel Sand & Gravel INC.; 2020-08-10 to current/open; source msha-controller-operator-history