# Relationship history for MSHA mine 0202687

Current hierarchy: **Peter Kiewit Sons' Inc → San Xavier Rock & Materials → PORTABLE CRUSHING & SCREENING PL**

- 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:** Peter Kiewit Sons' Inc → PORTABLE CRUSHING & SCREENING PL; 1989-12-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** San Xavier Rock & Materials → PORTABLE CRUSHING & SCREENING PL; 1997-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Peter Kiewit Sons' Inc → San Xavier Rock & Materials; 1997-04-01 to current/open; source msha-controller-operator-history