# Relationship history for MSHA mine 4503771

Current hierarchy: **Mark  Marple; Robert  O'Brien → Boulder Northwest Sand & Gravel, LLC → Boulder Northwest Sand & Gravel**

- 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:** Boulder Northwest Sand & Gravel, LLC → Boulder Northwest Sand & Gravel; 2017-03-21 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Mark  Marple et al → Boulder Northwest Sand & Gravel; 2017-03-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Mark  Marple et al → Boulder Northwest Sand & Gravel, LLC; 2017-03-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Robert  O'Brien et al → Boulder Northwest Sand & Gravel, LLC; 2017-03-21 to current/open; source msha-controller-operator-history