# Relationship history for MSHA mine 2800973

Current hierarchy: **Ralph Clayton & Sons Material Lp; Great Lakes Dredge & Dock LLC → Amboy Aggregates J.V. → Amboy Aggregates**

- 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:** Amboy Aggregates J.V. → Amboy Aggregates; 1985-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Ralph Clayton & Sons Material Lp et al → Amboy Aggregates; 1985-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ralph Clayton & Sons Material Lp et al → Amboy Aggregates J.V.; 1985-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Great Lakes Dredge & Dock LLC  et al → Amboy Aggregates J.V.; 1985-08-01 to current/open; source msha-controller-operator-history