# Relationship history for MSHA mine 3001250

Current hierarchy: **Ralph E  Porter → Porters' Sand & Gravel → Pit #2**

- 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:** Lycoming Silica Sand Company → Pit #2; 1950-01-01 to 1987-07-14; source msha-controller-operator-history
- **controller_controls_mine:** Koppers Company Inc → Pit #2; 1950-01-01 to 1988-11-13; source msha-controller-operator-history
- **controller_controls_operator:** Koppers Company Inc → Lycoming Silica Sand Company; 1950-01-01 to 1987-07-14; source msha-controller-operator-history
- **controller_controls_mine:** Ralph E  Porter → Pit #2; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Porters' Sand & Gravel → Pit #2; 1987-07-15 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ralph E  Porter → Porters' Sand & Gravel; 1987-07-15 to current/open; source msha-controller-operator-history