# Relationship history for MSHA mine 3800138

Current hierarchy: **USS Holdings Inc → U S Silica Company → COLUMBIA PLANT**

- 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:** Pennsylvania Glass Sand Corp → COLUMBIA PLANT; 1950-01-01 to 1986-05-14; source msha-controller-operator-history
- **controller_controls_mine:** ITT Corp → COLUMBIA PLANT; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** ITT Corp → Pennsylvania Glass Sand Corp; 1950-01-01 to 1986-05-14; source msha-controller-operator-history
- **controller_controls_mine:** Rio Tinto Group → COLUMBIA PLANT; 1986-04-02 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** U S Silica Company → COLUMBIA PLANT; 1986-05-15 to 1996-03-08; source msha-controller-operator-history
- **controller_controls_operator:** Rio Tinto Group → U S Silica Company; 1986-05-15 to 1996-03-08; source msha-controller-operator-history
- **operator_operates_mine:** U S Silica Company → COLUMBIA PLANT; 1996-03-09 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** USS Holdings Inc → COLUMBIA PLANT; 1996-03-09 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** USS Holdings Inc → U S Silica Company; 1996-03-09 to current/open; source msha-controller-operator-history