# Relationship history for MSHA mine 3503054

Current hierarchy: **Pacific Summa Environmental Corp → Bristol Silica & Limestone Company → Bristol Silica & Limestone 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

- **controller_controls_mine:** Nukka Oscar & Mike Bird → Bristol Silica & Limestone Mill; 1950-01-01 to 1983-07-31; source msha-controller-operator-history
- **operator_operates_mine:** Bristol Silica & Limestone Company → Bristol Silica & Limestone Mill; 1981-03-01 to 1982-12-20; source msha-controller-operator-history
- **controller_controls_operator:** Nukka Oscar & Mike Bird → Bristol Silica & Limestone Company; 1981-03-01 to 1982-12-20; source msha-controller-operator-history
- **operator_operates_mine:** Bristol Silica & Limestone Company → Bristol Silica & Limestone Mill; 1982-12-21 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Pacific Summa Environmental Corp Et Al → Bristol Silica & Limestone Mill; 1982-12-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Pacific Summa Environmental Corp Et Al → Bristol Silica & Limestone Company; 1982-12-21 to current/open; source msha-controller-operator-history