# Relationship history for MSHA mine 3609727

Current hierarchy: **Mark G Walworth; Ted  Walworth → Walworth Quarries → Portable**

- 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:** Ted  Walworth et al → Portable; 1999-10-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Walworth Quarries → Portable; 2009-03-20 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ted  Walworth et al → Walworth Quarries; 2009-03-20 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Mark G Walworth et al → Walworth Quarries; 2009-03-20 to current/open; source msha-controller-operator-history