# Relationship history for MSHA mine 4501707

Current hierarchy: **Taiheiyo Cement Corp → CalPortland Company → VASHON SAND AND GRAVEL 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: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **operator_operates_mine:** Vashon Sand & Gravel → VASHON SAND AND GRAVEL dba CalPortland; 1950-01-01 to 2004-09-16; source msha-controller-operator-history
- **controller_controls_mine:** Cliff  Alton → VASHON SAND AND GRAVEL dba CalPortland; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Cliff  Alton → Vashon Sand & Gravel; 1950-01-01 to 2004-09-16; source msha-controller-operator-history
- **controller_controls_mine:** Taiheiyo Cement Corp → VASHON SAND AND GRAVEL dba CalPortland; 1988-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Taiheiyo Cement Corp → VASHON SAND AND GRAVEL dba CalPortland; 1990-10-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Glacier Northwest Inc → VASHON SAND AND GRAVEL dba CalPortland; 2004-09-17 to 2009-07-30; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → Glacier Northwest Inc; 2004-09-17 to 2009-07-30; source msha-controller-operator-history
- **operator_operates_mine:** CalPortland Company → VASHON SAND AND GRAVEL dba CalPortland; 2009-07-31 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → CalPortland Company; 2009-07-31 to current/open; source msha-controller-operator-history