# Relationship history for MSHA mine 4501761

Current hierarchy: **Whatcom County-Wa → Whatcom County Public Works → Bluebird Pit**

- 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

- **controller_controls_mine:** Whatcom County-Wa → Bluebird Pit; 1978-03-09 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Whatcom County Public Works → Bluebird Pit; 1979-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Whatcom County-Wa → Whatcom County Public Works; 1979-10-01 to current/open; source msha-controller-operator-history