# Mills Plant

- **MSHA mine ID:** 4800617
- **Status:** Active
- **Type / commodity:** Facility / Bentonite
- **Location:** Natrona, WY
- **Operator:** Black Hills Bentonite
- **Controller:** BHB Limited Partnership; A&M Products
- **Public source rows linked:** 1,522
- **Source coverage:** 15 / 20
- **Generated:** 2026-10-13T11:26:59.401Z

## Current entity hierarchy

**BHB Limited Partnership; A&M Products (0167941) → Black Hills Bentonite (L09605) → Mills Plant (4800617)**

Current identity source: `msha-mines`. This is a current snapshot, not a historical claim.

## Controller and operator valid-time history

- **Yara Engineering Corp → Benton Clay Company:** 1950-01-01 through 1980-12-03; derived from co-tenure at mine 4800617; source `msha-controller-operator-history`.
- **Asea Brown Boveri Ltd (ABB) → Benton Clay Company:** 1980-12-04 through 1984-06-14; derived from co-tenure at mine 4800617; source `msha-controller-operator-history`.
- **T A  Thorson → Kaycee Bentonite Corp:** 1984-06-15 through 1986-12-31; derived from co-tenure at mine 4800617; source `msha-controller-operator-history`.
- **Thomas A  Thorson et al → Black Hills Bentonite:** 1987-01-01 through 2020-06-30; derived from co-tenure at mine 4800617; source `msha-controller-operator-history`.
- **BHB Limited Partnership et al → Black Hills Bentonite:** 2020-07-01 through current/open; derived from co-tenure at mine 4800617; source `msha-controller-operator-history`.
- **A&M Products et al → Black Hills Bentonite:** 2020-07-01 through current/open; derived from co-tenure at mine 4800617; source `msha-controller-operator-history`.

- History rows: 6
- Typed edges: 15
- Interval anomalies: 0
- Valid-time bounds: inclusive; date granularity; null end means open-ended in the upstream history row; not independent proof of present control.
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00.

## Assessment signals

1. **SAFETY — 6 since 2021:** Accidents and injuries 68 historical accident/injury rows; 0 coded fatalities and 1,904 lost days across the published record.
2. **COMPLIANCE — 66 since 2021:** Violations and penalties 278 violation rows across the full record; 97 carry an S&S flag and $133,989 appears in current assessed amounts.
3. **HEALTH — 50 samples:** Occupational health samples 50 personal. 9 personal-sample rows have a published C/E ratio above 1; 0 noise rows have an action-level or PEL dose above 100%. These are separate measures, not a silica exceedance count. Silica results and sample status are shown separately.
4. **PRODUCTION — 0 tons:** Quarterly production and employment 14K employee hours and 24 summed average employees across reported subunits in the latest published quarter.
5. **LEGAL — 48 linked rows:** Contests, conferences and decisions 23 contested-violation rows, 23 civil-penalty docket/decision rows, and 2 conference records linked by issuance number.
6. **CONTRACTORS — 4 linked entities:** Contractors Contractors are linked through this mine’s violation or accident records. Their production and hours cover all their operations, so they are not included in this mine’s totals.
7. **INSPECTIONS — 17 since 2021:** Inspections 99 inspection events and 2K published inspection hours across the historical record.

## EIA annual operating context

No matched record in the 2024 EIA coal-public workbook. This may be inapplicable for a non-coal operation.

## Recent Title 30 crosswalk

Snapshot current through 2026-08-19.

- **30 CFR 56.12028 — Testing grounding systems.** (2 retained recent rows) — https://www.ecfr.gov/current/title-30/chapter-I/subchapter-K/part-56/subpart-K/section-56.12028
- **30 CFR 56.20003 — Housekeeping.** (2 retained recent rows) — https://www.ecfr.gov/current/title-30/chapter-I/subchapter-K/part-56/subpart-S/section-56.20003
- **30 CFR 56.12018 — Identification of power switches.** (2 retained recent rows) — https://www.ecfr.gov/current/title-30/chapter-I/subchapter-K/part-56/subpart-K/section-56.12018
- **30 CFR 56.14115 — Stationary grinding machines.** (1 retained recent row) — https://www.ecfr.gov/current/title-30/chapter-I/subchapter-K/part-56/subpart-M/section-56.14115
- **30 CFR 56.16005 — Securing gas cylinders.** (1 retained recent row) — https://www.ecfr.gov/current/title-30/chapter-I/subchapter-K/part-56/subpart-O/section-56.16005
- **30 CFR 56.12008 — Insulation and fittings for power wires and cables.** (1 retained recent row) — https://www.ecfr.gov/current/title-30/chapter-I/subchapter-K/part-56/subpart-K/section-56.12008
- **30 CFR 56.14107 — Moving machine parts.** (2 retained recent rows) — https://www.ecfr.gov/current/title-30/chapter-I/subchapter-K/part-56/subpart-M/section-56.14107
- **30 CFR 56.4201 — Inspection.** (1 retained recent row) — https://www.ecfr.gov/current/title-30/chapter-I/subchapter-K/part-56/subpart-C/section-56.4201

## Source coverage

- **Accident, Injuries, and Illnesses:** 68 rows; 2000-04-14 through 2025-05-11; source ID `msha-accidents`
- **Addresses of Record:** 1 rows; 1990-10-26 through 1990-10-26; source ID `msha-addresses`
- **Assessed Violations:** 276 rows; 2000-03-28 through 2026-05-05; source ID `msha-assessed-violations`
- **Civil Penalty Dockets and Decisions:** 23 rows; 2004-11-23 through 2023-07-11; source ID `msha-civil-penalty-dockets-decisions`
- **Conferences:** 2 rows; 2002-04-23 through 2004-01-22; source ID `msha-conferences`
- **Contested Violations:** 23 rows; 2003-01-02 through 2022-12-13; source ID `msha-contested-violations`
- **Contractor Employment and Production — Quarterly:** 356 rows; unknown through unknown; source ID `msha-contractor-production-quarterly`
- **Contractor Employment and Production — Yearly:** 73 rows; unknown through unknown; source ID `msha-contractor-production-yearly`
- **Controller and Operator History:** 6 rows; 1950-01-01 through 1987-01-01; source ID `msha-controller-operator-history`
- **Inspections:** 99 rows; 2000-03-28 through 2026-08-03; source ID `msha-inspections`
- **Mine Employment and Production — Quarterly:** 212 rows; unknown through unknown; source ID `msha-mine-production-quarterly`
- **Mine Employment and Production — Yearly:** 54 rows; unknown through unknown; source ID `msha-mine-production-yearly`
- **Mines:** 1 rows; unknown through unknown; source ID `msha-mines`
- **Metal and Nonmetal Personal Health Samples:** 50 rows; 2001-01-10 through 2025-12-16; source ID `msha-personal-health-samples`
- **Violations:** 278 rows; 2000-03-28 through 2026-05-05; source ID `msha-violations`

## Caveats

- This is public-record decision support, not legal advice or an official MSHA record.
- Missing data can indicate no event, publication delay, an unresolved identity, or inapplicability.
- Contractor production data is entity-level and is not attributed to this mine.

## Alternate representations

- HTML: `/mines/mills-plant-4800617`
- JSON: `/api/v1/mines/mills-plant-4800617`
- Silica records, units, sample status and quarterly means: `/api/v1/mines/4800617/silica` (snapshot year by default; `?year=all` for history; `&format=csv` for all matching rows)
- Relationship JSON: `/api/v1/mines/4800617/relationships`
- MCP resource: `mine://4800617/assessment`
- Complete Title 30 corpus: `/data/title30-sections.json`