# Relationship history for MSHA mine 2602074

Current hierarchy: **Washington Group International Inc → Industrial Constructors Corp → BULLFROG MINE**

- 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:** Washington Group International Inc → BULLFROG MINE; 1988-02-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Industrial Constructors Corp → BULLFROG MINE; 1988-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Washington Group International Inc → Industrial Constructors Corp; 1988-08-01 to current/open; source msha-controller-operator-history