MINE DETAILS
Twin Underground
MSHA MINE ID2602693
LOCATION
Mine location
1 of 1 mine with usable MSHA coordinates. Select a marker to open a mine.
Mine coordinates
- Twin Underground41.21528, -117.18667Open map ↗
Quarterly trends
2025 Q1 – 2026 Q4
Database snapshot · 2026-10-13. MSHA quarterly production and employment reports.
Coal production
0reported short tons
Hours worked
4,892reported employee hours
Tons per hour
0.00production ÷ hours worked
Missing values appear as —. Totals use available reports. Tons per hour requires production and hours for the same quarters and a nonzero hours total. * Striped bars mark partial mine coverage or an incomplete quarter. See the table for coverage.
Quarterly data and reporting coverage
| Quarter | Coal (short tons) | Hours worked | Tons / hour | Avg. employees | Coverage |
|---|---|---|---|---|---|
| 2025 Q1 | 0 | 990 | 0.00 | 2 | 1/1 mines reporting |
| 2025 Q2 | 0 | 1,054 | 0.00 | 2 | 1/1 mines reporting |
| 2025 Q3 | 0 | 889 | 0.00 | 2 | 1/1 mines reporting |
| 2025 Q4 | 0 | 1,273 | 0.00 | 2 | 1/1 mines reporting |
| 2026 Q1 | 0 | 495 | 0.00 | 1 | 1/1 mines reporting |
| 2026 Q2 | 0 | 191 | 0.00 | 1 | 1/1 mines reporting |
| 2026 Q3 | — | — | — | — | No report |
| 2026 Q4 | — | — | — | — | No report |
Safety and enforcement
2025-01-01 – 2026-10-13
Violations
100 significant & substantial (S&S)
Accident records
20 records classified as fatality
Proposed penalties · USD
3,293.0010 of 10 violations with amounts
On-site inspection hours
65.0011 inspections · 11 with hours
Counts are published records, including contractor records. * The quarter was incomplete at the snapshot date; recent counts may rise as reports arrive. — means no reported amount or hours. Portfolio totals use current membership.
Quarterly safety data
| Quarter | Violations | S&S | Proposed USD | Accident records | Fatality records | Inspections | On-site hours |
|---|---|---|---|---|---|---|---|
| 2025-Q1 | 0 | 0 | — | 0 | 0 | 1 | 1.8 |
| 2025-Q2 | 1 | 0 | 151.00 | 0 | 0 | 1 | 3.5 |
| 2025-Q3 | 2 | 0 | 464.00 | 0 | 0 | 2 | 7.0 |
| 2025-Q4 | 2 | 0 | 344.00 | 0 | 0 | 3 | 16.3 |
| 2026-Q1 | 1 | 0 | 151.00 | 1 | 0 | 1 | 10.5 |
| 2026-Q2 | 3 | 0 | 2,032.00 | 0 | 0 | 1 | 16.0 |
| 2026-Q3 | 1 | 0 | 151.00 | 1 | 0 | 1 | 10.0 |
| 2026-Q4 * | 0 | 0 | — | 0 | 0 | 1 | 0.0 |
Most cited CFR sections
All violations issued in the selected period. Counts combine subsections.
Safety activity
Regular Safety and Health Inspection · 0.0 on-site hours
HANDTOOLS (NONPOWERED) · DAYS RESTRICTED ACTIVITY ONLY
Accident narrative
EE was loosening bolt on pot head when the wrench slipped and pinched their left index finger between the wrench and the pot head. EE reported incident on DOI. Seen at clinic 8/7, diagnosed with left index finger fracture, referred to orthopedics. Released to restrictions which are being accommodated.
Regular Safety and Health Inspection · 10.0 on-site hours
41.13 · $151.00 proposed
57.4201(a)(5) · $755.00 proposed
57.4104(a) · $1,126.00 proposed
47.41(a) · $151.00 proposed
Regular Safety and Health Inspection · 16.0 on-site hours
HANDLING OF MATERIALS · DAYS AWAY FROM WORK ONLY
Accident narrative
Miners were attempting to remove an old pump discharge pipe. The upstream valve had been isolated. While loosening the 4-inch Victaulic fitting, the pipe separated due to tension within the line, causing one of the pipes to swing toward the employee, striking EE in the right lower chest.
Regular Safety and Health Inspection · 10.5 on-site hours
57.4360(b) · $151.00 proposed
Compliance Follow-up Inspection · 0.5 on-site hours
57.14112(b) · $151.00 proposed
Ventilation Technical Investigation · 8.8 on-site hours
Regular Safety and Health Inspection · 7.0 on-site hours
57.12032 · $193.00 proposed
Compliance Follow-up Inspection · 0.5 on-site hours
Regular Safety and Health Inspection · 6.5 on-site hours
62.170(b) · $151.00 proposed
57.14100(b) · $313.00 proposed
Regular Safety and Health Inspection · 3.5 on-site hours
57.20014 · $151.00 proposed
Regular Safety and Health Inspection · 1.8 on-site hours
Safety sources and definitions
MSHA Violations (issue date), Accidents (accident date), and Inspections (begin date). Snapshot 2026-10-13.
Counts describe published rows, including contractor records; accident records are not distinct incidents or numbers of people injured.
Zero means no matching records in the imported sources, not proof of no events. Historical coverage differs by source; absence before a source begins reporting is not a zero incident rate. Invalid or absent dates and records after the snapshot are excluded.
S&S means SIG_SUB=Y. Fatality records use DEGREE_INJURY_CD=01. Proposed penalties are not final assessed or paid amounts; missing dollar values are omitted.
Inspection hours are SUM_TOTAL_ON_SITE_HOURS attributed to the inspection start date, without supervisor/trainee hours. Missing hours are omitted; a started inspection may still be open.
Portfolio totals use current mine membership, including events before the current owner or operator's tenure.
CFR headings link to the current Title 30 index; they are not historical legal determinations.
OWNERSHIP
Operator and controller history
Current ownership comes from MSHA Mines. Historical start and end dates come from MSHA Controller and Operator History.
—
Newmont USA Limited et alcontrolsNevada Gold Mines LLCoperatesTwin Underground
msha-controller-operator-history · controller/operator co-tenure derived on mine 2602693—
Barrick Nevada Holding LLC et alcontrolsNevada Gold Mines LLCoperatesTwin Underground
msha-controller-operator-history · controller/operator co-tenure derived on mine 2602693—
Newmont CorporationcontrolsNewmont USA LimitedoperatesTwin Underground
msha-controller-operator-history · controller/operator co-tenure derived on mine 2602693—
Keith JonescontrolsSmall Mine Development LLCoperatesTwin Underground
msha-controller-operator-history · controller/operator co-tenure derived on mine 2602693—
Ronald W GuillcontrolsSmall Mine Development LLCoperatesTwin Underground
msha-controller-operator-history · controller/operator co-tenure derived on mine 2602693Other historical summaries · source-specific periods
RECORD SUMMARY
Production, safety and enforcement
These summaries use the periods stated on each card, independently of the reporting period above.
01 / SAFETYwatch
Accidents and injuries
11 historical accident/injury rows; 0 coded fatalities and 79 lost days across the published record.
ACCIDENT + INJURY RECORD5 since 2021
accidentsmine-production-quarterly02 / COMPLIANCEwatch
Violations and penalties
132 violation rows across the full record; 13 carry an S&S flag and $144,606 appears in current assessed amounts.
ENFORCEMENT ACTIVITY66 since 2021
inspectionsviolationsassessed-violationsorders-107a03 / HEALTHwatch
Occupational health samples
29 personal; 3 area. 3 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.
OCCUPATIONAL EXPOSURE32 samples
personal-health-samplesarea-samples04 / PRODUCTIONcontext
Quarterly production and employment
191 employee hours and 1 summed average employees across reported subunits in the latest published quarter.
2026-Q20 tons
mine-production-quarterlymine-production-yearly05 / LEGALwatch
Contests, conferences and decisions
11 contested-violation rows, 12 civil-penalty docket/decision rows, and 12 conference records linked by issuance number.
POST-ISSUANCE LIFECYCLE35 linked rows
conferencescontested-violationscivil-penalty-dockets-decisions06 / CONTRACTORScontext
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.
ENTITY-LEVEL CONTEXT5 linked entities
contractor-production-quarterlycontractor-production-yearlyaccidentsviolations07 / INSPECTIONScontext
Inspections
79 inspection events and 2K published inspection hours across the historical record.
OVERSIGHT COVERAGE40 since 2021
inspectionsviolationsHEALTH SAMPLING
Silica and quartz
Coal quartz, metal/nonmetal personal samples and area samples. Snapshot Oct 13, 2026. 9 silica records across the mine’s published history.
Personal silica samples · concentration / limit
Quarterly mean · published C/E ratio
— No eligible measurements. * Quarter in progress. Means describe the available samples, not average exposure across the mine.
Quartz % is the sample’s quartz content; µg/m³ is its reported concentration. Personal C/E is the ratio to the limit published with that sample. Personal and area concentration units and void status are not specified in those source files.
| Date / sample | Dataset / analyte | Occupation / area | Measurement | Sample status | Published action |
|---|---|---|---|---|---|
| 000000202601480900 | Metal/nonmetal personalQuartz, respirable, >1% Qtz | Scoop-Tram Operator | 0.54× published limitConcentration: 0000.88 · limit: 0001.64Source unit unspecified | Not reported | NO ACTIONInspection F011AD4 |
| 000000202601481000 | Metal/nonmetal personalQuartz, respirable, >1% Qtz | Truck Driver | 0.41× published limitConcentration: 0000.47 · limit: 0001.14Source unit unspecified | Not reported | NO ACTIONInspection F011AD4 |
Sources and interpretation
- Coal means use numeric concentrations from samples marked not voided, excluding control/invalid sample types and dates after the snapshot. Missing values remain null; reported zeroes remain zero.
- Quarterly means describe available samples, not mine-wide or worker-average exposure. Quarters with no eligible measurements remain empty; the current quarter is partial.
- Personal C/E is MSHA's published concentration-to-limit ratio. A value above 1 is not by itself a citation or a determination under the 2024 silica rule. Personal and area files do not publish a void-status field.
- Area records include bulk-dust analyses and are kept separate from personal exposure results. Their concentration units are not specified in the source dictionary.
- Missing samples do not establish safe conditions. Coal quartz percentage and concentration are separate measures. No compliance threshold is inferred for coal samples.
Coal quartz field definitions ↗Metal/nonmetal personal field definitions ↗Metal/nonmetal area field definitions ↗
EIA + TITLE 30
EIA production and cited regulations
EIA annual figures are reported separately from MSHA. Regulation links use the current eCFR snapshot.
Not present in the 2024 EIA coal workbook.
This can mean the operation is non-coal, inactive for the annual period, or outside the EIA-7A reporting population.
30 CFR 41.13Failure to notify.1 recent row ↗30 CFR 57.4201Inspection.1 recent row ↗30 CFR 57.4104Combustible waste.2 recent rows ↗30 CFR 47.41Requirement for container labels.1 recent row ↗30 CFR 57.4360Underground alarm systems.1 recent row ↗30 CFR 57.14112Construction and maintenance of guards.1 recent row ↗30 CFR 57.12032Inspection and cover plates.1 recent row ↗30 CFR 62.170Audiometric testing.1 recent row ↗
RECENT PUBLIC RECORDS
Recent violations and samples
Latest records retained for inspection; aggregates above use the full source history.
510949841.13Citation
510945757.4201(a)(5)Citation
510945657.4104(a)Citation
510945547.41(a)Citation
510941257.4360(b)Citation
510516857.14112(b)Citation
516802257.12032Citation
510436462.170(b)Citation
Coal dust, noise and other contaminants. Silica records above ↑
EC @ 160Truck Driver
C/E: 00.00Concentration: 0000.00 · limit: 0160.00Source unit unspecified
TC from EC @ 160Truck Driver
C/E: 00.00Concentration: 0000.00 · limit: 0160.00Source unit unspecified
TC @ 160Truck Driver
C/E: 00.00Concentration: 0000.00 · limit: 0160.00Source unit unspecified
EC @ 160Complete Load-Haul-Dump
C/E: 00.00Concentration: 0000.00 · limit: 0160.00Source unit unspecified
TC from EC @ 160Complete Load-Haul-Dump
C/E: 00.00Concentration: 0000.00 · limit: 0160.00Source unit unspecified
TC @ 160Complete Load-Haul-Dump
C/E: 00.20Concentration: 0032.00 · limit: 0160.00Source unit unspecified
SOURCE COVERAGE
Reporting dates and coverage
16 datasets contain linked records. Missing datasets are listed below.
DATASETROWSWINDOWSTATUS
Accident, Injuries, and Illnessessafety · contractors11Mar 6, 2013—Aug 1, 2026mine-keyed
Addresses of Recordidentity · logistics1Nov 26, 2024—Nov 26, 2024mine-keyed
Assessed Violationscompliance · legal130Jun 22, 2011—Jul 22, 2026mine-keyed
Civil Penalty Dockets and Decisionscompliance · legal12Dec 11, 2012—Apr 14, 2023mine-keyed
Coal Dust Sampleshealth · safety—No published rowsabsent / not applicable
Conferencescompliance · legal12Feb 3, 2014—Jun 16, 2026mine-keyed
Contested Violationscompliance · legal11Jun 7, 2011—Sep 16, 2022mine-keyed
Contractor Employment and Production — Quarterlycontractors · production · safety907Not published—Not publishedentity-linked
Contractor Employment and Production — Yearlycontractors · production · safety208Not published—Not publishedentity-linked
Controller and Operator Historyidentity · compliance5Feb 22, 2011—Jul 29, 2019mine-keyed
Mine Employment and Production — Quarterlyproduction · safety · compliance79Not published—Not publishedmine-keyed
Mine Employment and Production — Yearlyproduction · safety · compliance18Not published—Not publishedmine-keyed
Inspectionssafety · compliance79Jun 7, 2011—Oct 5, 2026mine-keyed
Minesidentity · production · logistics1Not published—Not publishedmine-keyed
Metal and Nonmetal Area Sampleshealth · safety3Nov 15, 2017—Nov 15, 2017mine-keyed
Metal and Nonmetal Personal Health Sampleshealth · safety29Mar 26, 2013—Apr 8, 2026mine-keyed
Noise Sampleshealth · safety · equipment—No published rowsabsent / not applicable
Quartz Samples — Coalhealth · safety—No published rowsabsent / not applicable
Violationscompliance · safety · legal132Jun 22, 2011—Jul 22, 2026mine-keyed
107(a) Orders Issuedsafety · compliance—No published rowsabsent / not applicable
NOTES
Limitations
- Contractor production is entity-level and is never represented as mine-attributable.
- Missing rows can mean no event, publication delay, identity mismatch, or inapplicability.