# Relationship history for MSHA mine 3200144

Current hierarchy: **Wachter Lance → Dakota Sand & Gravel Company → Riverdale Portable Plant**

- 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

- **controller_controls_mine:** Wachter James → Riverdale Portable Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Dakota Sand & Gravel Company → Riverdale Portable Plant; 1985-06-01 to 1986-05-07; source msha-controller-operator-history
- **controller_controls_operator:** Wachter James → Dakota Sand & Gravel Company; 1985-06-01 to 1986-05-07; source msha-controller-operator-history
- **operator_operates_mine:** Dakota Sand & Gravel Company → Riverdale Portable Plant; 1986-05-08 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Wachter Lance → Riverdale Portable Plant; 1986-05-08 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Wachter Lance → Dakota Sand & Gravel Company; 1986-05-08 to current/open; source msha-controller-operator-history