# Relationship history for MSHA mine 4104186

Current hierarchy: **Donald L  Poarch; Joseph B  Swinbank → Sprint Sand & Clay L P → Friendswood Sandpit**

- 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:** Donald L  Poarch et al → Friendswood Sandpit; 1989-02-28 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Sprint Sand & Clay L P → Friendswood Sandpit; 2000-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Donald L  Poarch et al → Sprint Sand & Clay L P; 2000-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Joseph B  Swinbank et al → Sprint Sand & Clay L P; 2000-08-01 to current/open; source msha-controller-operator-history