# Relationship history for MSHA mine 3700156

Current hierarchy: **David  D'Ambra → Richmond Sand & Stone LLC → Richmond Sand & Stone**

- 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:** Richmond Sand & Gravel Inc → Richmond Sand & Stone; 1980-09-01 to 2005-06-19; source msha-controller-operator-history
- **controller_controls_mine:** Jeffrey W  Nero → Richmond Sand & Stone; 1980-09-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Jeffrey W  Nero → Richmond Sand & Gravel Inc; 1980-09-01 to 2005-06-19; source msha-controller-operator-history
- **operator_operates_mine:** Richmond Sand & Gravel Inc → Richmond Sand & Stone; 2005-06-20 to 2009-07-06; source msha-controller-operator-history
- **controller_controls_mine:** Peter A Calcagni → Richmond Sand & Stone; 2005-06-20 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Peter A Calcagni → Richmond Sand & Gravel Inc; 2005-06-20 to 2009-07-06; source msha-controller-operator-history
- **operator_operates_mine:** Richmond Sand & Stone LLC → Richmond Sand & Stone; 2009-07-07 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Mike D  D'Ambra et al → Richmond Sand & Stone; 2009-07-07 to 2017-11-30; source msha-controller-operator-history
- **controller_controls_operator:** Mike D  D'Ambra et al → Richmond Sand & Stone LLC; 2009-07-07 to 2017-11-30; source msha-controller-operator-history
- **controller_controls_operator:** Robert A  D'Ambra et al → Richmond Sand & Stone LLC; 2009-07-07 to 2017-11-30; source msha-controller-operator-history
- **controller_controls_mine:** David  D'Ambra → Richmond Sand & Stone; 2017-12-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** David  D'Ambra → Richmond Sand & Stone LLC; 2017-12-01 to current/open; source msha-controller-operator-history