# Relationship history for MSHA mine 1600984

Current hierarchy: **Hanson PLC → Gifford-Hill & Company → Heflin 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: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **controller_controls_mine:** Hanson PLC → Heflin Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Tri-State Sand & Gravel Inc → Heflin Plant; 1980-04-01 to 1987-05-10; source msha-controller-operator-history
- **controller_controls_mine:** Frank B  Treat Jr → Heflin Plant; 1980-04-01 to 1987-05-10; source msha-controller-operator-history
- **controller_controls_operator:** Frank B  Treat Jr → Tri-State Sand & Gravel Inc; 1980-04-01 to 1987-05-10; source msha-controller-operator-history
- **operator_operates_mine:** Tri-State Sand & Gravel Inc → Heflin Plant; 1987-05-11 to 1988-04-06; source msha-controller-operator-history
- **controller_controls_mine:** Edward  Kennon → Heflin Plant; 1987-05-11 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Edward  Kennon → Tri-State Sand & Gravel Inc; 1987-05-11 to 1988-04-06; source msha-controller-operator-history
- **operator_operates_mine:** Gifford-Hill & Company → Heflin Plant; 1988-04-07 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hanson PLC → Gifford-Hill & Company; 1988-04-07 to current/open; source msha-controller-operator-history