# Relationship history for MSHA mine 2600724

Current hierarchy: **Mendel Lisa → Valley Rock & Sand Inc → VALLEY ROCK PIT**

- 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:** Valley Sand & Gravel Company → VALLEY ROCK PIT; 1950-01-01 to 1983-07-18; source msha-controller-operator-history
- **controller_controls_mine:** Olson Donald → VALLEY ROCK PIT; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Olson Donald → Valley Sand & Gravel Company; 1950-01-01 to 1983-07-18; source msha-controller-operator-history
- **operator_operates_mine:** Calhoon'S Sand & Gravel → VALLEY ROCK PIT; 1983-07-19 to 1997-07-30; source msha-controller-operator-history
- **controller_controls_mine:** Calhoon Lee → VALLEY ROCK PIT; 1983-07-19 to 1997-07-30; source msha-controller-operator-history
- **controller_controls_operator:** Calhoon Lee → Calhoon'S Sand & Gravel; 1983-07-19 to 1997-07-30; source msha-controller-operator-history
- **operator_operates_mine:** Valley Rock & Sand Inc → VALLEY ROCK PIT; 1997-07-31 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Mendel Lisa Et Al → VALLEY ROCK PIT; 1997-07-31 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Mendel Lisa Et Al → Valley Rock & Sand Inc; 1997-07-31 to current/open; source msha-controller-operator-history