# Relationship history for MSHA mine 3002409

Current hierarchy: **Michael D  Austin → Austin Sand & Gravel → Porter's Pit**

- 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:** Ralph E  Porter → Porter's Pit; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Porters' Sand & Gravel → Porter's Pit; 1979-01-01 to 2024-07-16; source msha-controller-operator-history
- **controller_controls_operator:** Ralph E  Porter → Porters' Sand & Gravel; 1979-01-01 to 2024-07-16; source msha-controller-operator-history
- **controller_controls_mine:** Michael D  Austin → Porter's Pit; 2014-10-30 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Austin Sand & Gravel → Porter's Pit; 2024-07-17 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Michael D  Austin → Austin Sand & Gravel; 2024-07-17 to current/open; source msha-controller-operator-history