# Relationship history for MSHA mine 3503537

Current hierarchy: **Taiheiyo Cement Corp → CalPortland Company → Bluelake DBA CalPortland**

- 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

- **controller_controls_mine:** Taiheiyo Cement Corp → Bluelake DBA CalPortland; 1988-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Taiheiyo Cement Corp → Bluelake DBA CalPortland; 1990-10-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Glacier Northwest → Bluelake DBA CalPortland; 2001-08-01 to 2009-01-12; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → Glacier Northwest; 2001-08-01 to 2009-01-12; source msha-controller-operator-history
- **operator_operates_mine:** CalPortland Company → Bluelake DBA CalPortland; 2009-01-13 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → CalPortland Company; 2009-01-13 to current/open; source msha-controller-operator-history