# Relationship history for MSHA mine 5000689

Current hierarchy: **Knife River Corporation → Anchorage Sand & Gravel Company Inc → Birchwood Loading Station**

- 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:** Anchorage Sand & Gravel Company Inc → Birchwood Loading Station; 1950-01-01 to 2011-05-10; source msha-controller-operator-history
- **controller_controls_mine:** KRC Aggregate Inc → Birchwood Loading Station; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** KRC Aggregate Inc → Anchorage Sand & Gravel Company Inc; 1950-01-01 to 2011-05-10; source msha-controller-operator-history
- **controller_controls_mine:** MDU Resources Group Inc → Birchwood Loading Station; 1993-04-23 to 2023-05-31; source msha-controller-operator-history
- **operator_operates_mine:** Anchorage Sand & Gravel Company Inc → Birchwood Loading Station; 2011-05-11 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** MDU Resources Group Inc → Anchorage Sand & Gravel Company Inc; 2011-05-11 to 2023-05-31; source msha-controller-operator-history
- **controller_controls_mine:** Knife River Corporation → Birchwood Loading Station; 2023-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Knife River Corporation → Anchorage Sand & Gravel Company Inc; 2023-06-01 to current/open; source msha-controller-operator-history