# Relationship history for MSHA mine 3604031

Current hierarchy: **Snyder Associated Companies Inc → Glacial Sand & Gravel Company → Bridgeburg Dredge & Mill**

- 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

- **operator_operates_mine:** Glacial Sand & Gravel Company → Bridgeburg Dredge & Mill; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Snyder Associated Companies Inc → Bridgeburg Dredge & Mill; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Snyder Associated Companies Inc → Glacial Sand & Gravel Company; 1950-01-01 to current/open; source msha-controller-operator-history