# Relationship history for MSHA mine 3402090

Current hierarchy: **Andrew  Walker → Nicholson Construction Company → NCC Sand Plant Cleo Springs**

- 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:** Nicholson Construction Company → NCC Sand Plant Cleo Springs; 2009-08-20 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Andrew  Walker → NCC Sand Plant Cleo Springs; 2009-08-20 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Andrew  Walker → Nicholson Construction Company; 2009-08-20 to current/open; source msha-controller-operator-history