# Relationship history for MSHA mine 3304581

Current hierarchy: **CRH PLC → Shelly Materials Inc → Portland 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:** CRH PLC → Portland Plant; 2000-03-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Shelly Materials Inc → Portland Plant; 2007-02-28 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** CRH PLC → Shelly Materials Inc; 2007-02-28 to current/open; source msha-controller-operator-history