# Relationship history for MSHA mine 1302155

Current hierarchy: **Ash Grove Cement Company → Hartford Sand & Gravel Company → Portable #2**

- 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:** Ash Grove Cement Company → Portable #2; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Hartford Sand & Gravel Company → Portable #2; 1988-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ash Grove Cement Company → Hartford Sand & Gravel Company; 1988-04-01 to current/open; source msha-controller-operator-history