# Relationship history for MSHA mine 4101102

Current hierarchy: **Bill C  Burwick → Sweetwater Ready Mix Concrete Company → TexSand Gravel Products**

- 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:** Hillsdale Gravel Company → TexSand Gravel Products; 1950-01-01 to 1980-06-30; source msha-controller-operator-history
- **controller_controls_mine:** Fred C  Stevenson → TexSand Gravel Products; 1950-01-01 to 1980-06-30; source msha-controller-operator-history
- **controller_controls_operator:** Fred C  Stevenson → Hillsdale Gravel Company; 1950-01-01 to 1980-06-30; source msha-controller-operator-history
- **operator_operates_mine:** Sweetwater Ready Mix Concrete Company → TexSand Gravel Products; 1980-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Bill C  Burwick → TexSand Gravel Products; 1980-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Bill C  Burwick → Sweetwater Ready Mix Concrete Company; 1980-07-01 to current/open; source msha-controller-operator-history