# Relationship history for MSHA mine 2901997

Current hierarchy: **Salt River Project; MidAmerican Energy Holdings Company; Tri-State Gener → Williams Fork Mining Company → Fence Lake No 1**

- 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

- **operator_operates_mine:** Salt River Proj Agricultrl Improvmt & Power Dist → Fence Lake No 1; 1985-08-01 to 1986-09-02; source msha-controller-operator-history
- **controller_controls_mine:** Salt River Proj Agricultrl Improvmt & Power Dist → Fence Lake No 1; 1985-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Salt River Proj Agricultrl Improvmt & Power Dist → Salt River Proj Agricultrl Improvmt & Power Dist; 1985-08-01 to 1986-09-02; source msha-controller-operator-history
- **operator_operates_mine:** Williams Fork Mining Company → Fence Lake No 1; 1986-09-03 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Tri-State Generation & Transmsn Assoc et al → Fence Lake No 1; 1986-09-03 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Tri-State Generation & Transmsn Assoc et al → Williams Fork Mining Company; 1986-09-03 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Salt River Project et al → Williams Fork Mining Company; 1986-09-03 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** MidAmerican Energy Holdings Company et al → Williams Fork Mining Company; 1986-09-03 to current/open; source msha-controller-operator-history