# Relationship history for MSHA mine 2700342

Current hierarchy: **David  Blackmer → Earthworks Inc → EARTHWORKS PORTABLE CRUSHER**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Earthworks Inc → EARTHWORKS PORTABLE CRUSHER; 1999-09-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** David  Blackmer → EARTHWORKS PORTABLE CRUSHER; 1999-09-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** David  Blackmer → Earthworks Inc; 1999-09-01 to current/open; source msha-controller-operator-history