# Relationship history for MSHA mine 2401992

Current hierarchy: **Washington Companies → Pipestone Quarry, LLC → Pipestone Quarry**

- 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:** Washington Group International Inc → Pipestone Quarry; 1986-04-01 to 2007-11-14; source msha-controller-operator-history
- **operator_operates_mine:** URS Energy and Construction, Inc. → Pipestone Quarry; 1992-10-01 to 2015-10-04; source msha-controller-operator-history
- **controller_controls_operator:** Washington Group International Inc → URS Energy and Construction, Inc.; 1992-10-01 to 2007-11-14; source msha-controller-operator-history
- **controller_controls_mine:** URS Corporation → Pipestone Quarry; 2007-11-15 to 2014-12-31; source msha-controller-operator-history
- **controller_controls_operator:** URS Corporation → URS Energy and Construction, Inc.; 2007-11-15 to 2014-12-31; source msha-controller-operator-history
- **controller_controls_mine:** AECOM → Pipestone Quarry; 2015-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** AECOM → URS Energy and Construction, Inc.; 2015-01-01 to 2015-10-04; source msha-controller-operator-history
- **operator_operates_mine:** Pipestone Quarry, LLC → Pipestone Quarry; 2015-10-05 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Washington Companies → Pipestone Quarry; 2015-10-05 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Washington Companies → Pipestone Quarry, LLC; 2015-10-05 to current/open; source msha-controller-operator-history