# Relationship history for MSHA mine 4502725

Current hierarchy: **Willis R  Waldow → North Clark Construction → Columbia River Sand & Gravel Pit #3**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **operator_operates_mine:** North Clark Construction → Columbia River Sand & Gravel Pit #3; 1979-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Willis R  Waldow → Columbia River Sand & Gravel Pit #3; 1979-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Willis R  Waldow → North Clark Construction; 1979-01-01 to current/open; source msha-controller-operator-history