# Relationship history for MSHA mine 4503136

Current hierarchy: **Taiheiyo Cement Corp → CalPortland Company → Snoqualmie S&G dba CalPortland 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: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **operator_operates_mine:** Snoqualmie Sand & Gravel → Snoqualmie S&G dba CalPortland Company; 1987-07-01 to 1990-09-30; source msha-controller-operator-history
- **controller_controls_mine:** Jane A  Hallock → Snoqualmie S&G dba CalPortland Company; 1987-07-01 to 1990-09-30; source msha-controller-operator-history
- **controller_controls_operator:** Jane A  Hallock → Snoqualmie Sand & Gravel; 1987-07-01 to 1990-09-30; source msha-controller-operator-history
- **controller_controls_mine:** Taiheiyo Cement Corp → Snoqualmie S&G dba CalPortland Company; 1988-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Northwest Aggregates → Snoqualmie S&G dba CalPortland Company; 1990-10-01 to 2002-05-15; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → Northwest Aggregates; 1990-10-01 to 2002-05-15; source msha-controller-operator-history
- **controller_controls_mine:** Taiheiyo Cement Corp → Snoqualmie S&G dba CalPortland Company; 1990-10-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Glacier Northwest → Snoqualmie S&G dba CalPortland Company; 2002-05-16 to 2009-07-30; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → Glacier Northwest; 2002-05-16 to 2009-07-30; source msha-controller-operator-history
- **operator_operates_mine:** CalPortland Company → Snoqualmie S&G dba CalPortland Company; 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