# Relationship history for MSHA mine 1600975

Current hierarchy: **Hart Ronald → Ace Sand & Gravel Of Denham Springs → 4 Inch Dredge And 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

- **operator_operates_mine:** Ace Sand & Gravel Of Denham Springs → 4 Inch Dredge And Plant; 1980-02-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Hart Ronald → 4 Inch Dredge And Plant; 1980-02-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hart Ronald → Ace Sand & Gravel Of Denham Springs; 1980-02-01 to current/open; source msha-controller-operator-history