# Relationship history for MSHA mine 1901007

Current hierarchy: **Scott  Kimball; Wayne  Kimball → KIMBALL SAND COMPANY INC → BLACKSTONE 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:** Kimball Sand Company Inc → Blackstone Plant; 1987-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Robert W  Kimball → Blackstone Plant; 1987-01-01 to 2020-02-29; source msha-controller-operator-history
- **controller_controls_operator:** Robert W  Kimball → Kimball Sand Company Inc; 1987-01-01 to 2020-02-29; source msha-controller-operator-history
- **controller_controls_mine:** Wayne  Kimball et al → Blackstone Plant; 2020-03-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Wayne  Kimball et al → Kimball Sand Company Inc; 2020-03-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Scott  Kimball et al → Kimball Sand Company Inc; 2020-03-01 to current/open; source msha-controller-operator-history