# Relationship history for MSHA mine 3605097

Current hierarchy: **Charles E Frey; Bradley J Frey → Northwest Gravel Company → Northwest Gravel Company**

- 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:** Northwest Gravel Company → Northwest Gravel Company; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Charles E Frey et al → Northwest Gravel Company; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Charles E Frey et al → Northwest Gravel Company; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Bradley J Frey et al → Northwest Gravel Company; 1950-01-01 to current/open; source msha-controller-operator-history