# Relationship history for MSHA mine 4701146

Current hierarchy: **Treco Sales Inc → Bay City Silica Division/Treco Sales Inc → Bay City Silica**

- 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

- **operator_operates_mine:** Bay City Sand Company → Bay City Silica; 1950-01-01 to 1980-03-10; source msha-controller-operator-history
- **controller_controls_mine:** Boigenzahn Edward → Bay City Silica; 1950-01-01 to 1980-03-10; source msha-controller-operator-history
- **controller_controls_operator:** Boigenzahn Edward → Bay City Sand Company; 1950-01-01 to 1980-03-10; source msha-controller-operator-history
- **operator_operates_mine:** Bay City Silica Division/Treco Sales Inc → Bay City Silica; 1980-03-11 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Treco Sales Inc → Bay City Silica; 1980-03-11 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Treco Sales Inc → Bay City Silica Division/Treco Sales Inc; 1980-03-11 to current/open; source msha-controller-operator-history