# Relationship history for MSHA mine 4801539

Current hierarchy: **BHB Limited Partnership; A&M Products → Black Hills Bentonite → HT 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

- **controller_controls_mine:** Thomas A  Thorson et al → HT Plant; 1987-01-01 to 2020-06-30; source msha-controller-operator-history
- **operator_operates_mine:** Black Hills Bentonite → HT Plant; 1997-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Thomas A  Thorson et al → Black Hills Bentonite; 1997-07-01 to 2020-06-30; source msha-controller-operator-history
- **controller_controls_mine:** BHB Limited Partnership et al → HT Plant; 2020-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** BHB Limited Partnership et al → Black Hills Bentonite; 2020-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** A&M Products et al → Black Hills Bentonite; 2020-07-01 to current/open; source msha-controller-operator-history