# Relationship history for MSHA mine 1600489

Current hierarchy: **USS Holdings Inc → U.S. Silica Company, LLC → Dubberly 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:** Dresser Minerals Division → Dubberly Plant; 1950-01-01 to 1981-07-09; source msha-controller-operator-history
- **controller_controls_mine:** Dresser Industries Inc → Dubberly Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Dresser Industries Inc → Dresser Minerals Division; 1950-01-01 to 1981-07-09; source msha-controller-operator-history
- **operator_operates_mine:** Louisiana Industrial Sand Company → Dubberly Plant; 1981-07-10 to 1986-12-31; source msha-controller-operator-history
- **controller_controls_mine:** Ottawa Silica Company → Dubberly Plant; 1981-07-10 to 1986-12-31; source msha-controller-operator-history
- **controller_controls_operator:** Ottawa Silica Company → Louisiana Industrial Sand Company; 1981-07-10 to 1986-12-31; source msha-controller-operator-history
- **controller_controls_mine:** Rio Tinto Group → Dubberly Plant; 1986-04-02 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** U S Silica Company → Dubberly Plant; 1987-01-01 to 1996-03-08; source msha-controller-operator-history
- **controller_controls_operator:** Rio Tinto Group → U S Silica Company; 1987-01-01 to 1996-03-08; source msha-controller-operator-history
- **operator_operates_mine:** U S Silica Company → Dubberly Plant; 1996-03-09 to 2025-03-27; source msha-controller-operator-history
- **controller_controls_mine:** USS Holdings Inc → Dubberly 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 2025-03-27; source msha-controller-operator-history
- **operator_operates_mine:** U.S. Silica Energy Company → Dubberly Plant; 2025-03-28 to 2026-02-28; source msha-controller-operator-history
- **controller_controls_mine:** USS Holdings Inc → Dubberly Plant; 2025-03-28 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** USS Holdings Inc → U.S. Silica Energy Company; 2025-03-28 to 2026-02-28; source msha-controller-operator-history
- **operator_operates_mine:** U.S. Silica Company, LLC → Dubberly Plant; 2026-03-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** USS Holdings Inc → U.S. Silica Company, LLC; 2026-03-01 to current/open; source msha-controller-operator-history