# Relationship history for MSHA mine 2500281

Current hierarchy: **CRH PLC → Lyman-Richey Sand & Gravel Company → Plant #23 Bridgeport**

- 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

- **operator_operates_mine:** Lyman-Richey Sand & Gravel Company → Plant #23 Bridgeport; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Ash Grove Cement Company → Plant #23 Bridgeport; 1950-01-01 to 2018-06-20; source msha-controller-operator-history
- **controller_controls_operator:** Ash Grove Cement Company → Lyman-Richey Sand & Gravel Company; 1950-01-01 to 2018-06-20; source msha-controller-operator-history
- **controller_controls_mine:** CRH PLC → Plant #23 Bridgeport; 2018-06-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** CRH PLC → Lyman-Richey Sand & Gravel Company; 2018-06-21 to current/open; source msha-controller-operator-history