# Relationship history for MSHA mine 3901217

Current hierarchy: **Interstate Dairy Sales → Tjarden Sand & Gravel → Tjarden Sand & Gravel & 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: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **operator_operates_mine:** Salem Lumber Company → Tjarden Sand & Gravel & Plant; 1979-07-01 to 1980-05-08; source msha-controller-operator-history
- **controller_controls_mine:** Fligge Doug → Tjarden Sand & Gravel & Plant; 1979-07-01 to 1980-05-08; source msha-controller-operator-history
- **controller_controls_operator:** Fligge Doug → Salem Lumber Company; 1979-07-01 to 1980-05-08; source msha-controller-operator-history
- **operator_operates_mine:** Tjarden Sand & Gravel → Tjarden Sand & Gravel & Plant; 1980-05-09 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Interstate Dairy Sales → Tjarden Sand & Gravel & Plant; 1980-05-09 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Interstate Dairy Sales → Tjarden Sand & Gravel; 1980-05-09 to current/open; source msha-controller-operator-history