Pronghorn LLC; Isom Brothers Holding LLC: 118 MSHA citations controller
MSHA controller ID: 0170380
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Email me when a new MSHA incident is filed at any mine Pronghorn LLC; Isom Brothers Holding LLC controls.
- Fatalities
- 0
- Total incidents
- 9
- Mines on record
- 3
- Years on record
- 2022–2025
Compliance record
MSHA citations since 2022
118
citations
37
significant & substantial
$312,931
proposed penalties
$151,452
paid to date
48% of proposed penalties paid to date, a $161,479 gap.
Source: MSHA violations data, updated weekly.
Inspection activity
MSHA inspections since 2022
30
inspections on record
814
inspection hours
n/a
citations per 100 inspection hours
ⓘ
This rate is recorded citations divided by MSHA inspection hours, per 100 hours. It reflects inspection effort, not mine size or production.Rate withheld: 814 inspection hours is too few for a stable rate. A minimum of 1,000 inspection hours is required.
Source: MSHA inspections data, updated weekly.
Penalty disposition
ⓘ
Differences between proposed and paid penalties reflect both settlements and conference reductions and amounts still owed. Outstanding is the balance currently owed.$313K
proposed penalties
$240K
current assessed
$151K
paid to date
$88K
outstanding
115 assessments are final orders; 2 contested dockets.
Of $86K in penalties contested before the Commission, $13K was upheld in final decisions.
As of the most recent assessment on 2026-05-13.
Source: MSHA assessed-violations and conference/litigation data, updated weekly.
Violation severity profile
ⓘ
Shares are computed over citations that carry the MSHA gravity and negligence coding; a small share of records are uncoded.32.2%
significant & substantial
14.8%
high negligence or reckless
32.2%
reasonably likely or greater
67.0%
permanently disabling or fatal if injury occurs
Negligence coding: 0.9% none, 13.0% low, 71.3% moderate, 14.8% high, 0.0% reckless.
Source: MSHA violations gravity and negligence coding, updated weekly.
Injury rate, 2025
ⓘ
This rate is reportable injury cases per 100 full-time-equivalent workers per year, computed as 200,000 times cases divided by MSHA operator-reported employee-hours. Cases are injuries MSHA graded degree 01 through 07; accident-only events that hurt no one are excluded, and so are contractor injuries, whose hours do not attach to a single mine. Rates begin in 2000, when quarterly employment reporting starts, and are withheld below 20,000 hours in a year.2.52
total case rate
2.52
days-away rate
0.000
fatality rate
Above average. The US metal and nonmetal mining average was 1.65 and the all-US-mining average was 1.97 cases per 100 workers.
Under 100,000 employee-hours were reported that year, so a single case moves the rate by two or more. Read the figure as approximate.
| Year | total case rate | days-away | fatal |
|---|---|---|---|
| 2026 * | 0.00 | 0.00 | 0.000 |
| 2025 * | 2.52 | 2.52 | 0.000 |
| 2024 * | 0.00 | 0.00 | 0.000 |
| 2023 | 8.26 | 4.96 | 0.000 |
| 2022 * | 4.07 | 4.07 | 0.000 |
* Fewer than 100,000 employee-hours that year; the rate is less stable.
Source: injury cases from MSHA accident and injury records; employee-hours from MSHA quarterly employment reports. Rate is cases per 100 full-time-equivalent workers, operator employees only.
Health sampling
ⓘ
A sample is a point in time compliance measurement, not an individual exposure history. These figures describe MSHA sampling records and do not establish causation or personal dose.Metal and nonmetal contaminants (personal samples)
ⓘ
Many samples are screening measurements of substances with no applicable exposure limit; they are counted as samples but excluded from every over-limit figure. Over-limit shares use only limit-tested samples.
Last sampled: 2024-11-26
ⓘ
Many samples are screening measurements of substances with no applicable exposure limit; they are counted as samples but excluded from every over-limit figure. Over-limit shares use only limit-tested samples.40%
of limit-tested samples over the exposure limit
19
samples
5
limit-tested
Most sampled contaminants
- Quartz, respirable, >1% Qtz52 over
- Respirable dust, <.1mg14
Source: MSHA respirable dust, quartz, and noise sampling records, updated weekly. Metal/nonmetal contaminant figures come from MSHA's Personal Health Samples and Area Samples files (public record), updated weekly.
When citations were contested
ⓘ
Contesting a citation before the Federal Mine Safety and Health Review Commission is a lawful right. These figures state the public outcomes of that process, from MSHA's Contested Violations file.
19
citations taken to the federal commission · 16% of citations on record
- Settled 9 · 47%
- Stood as issued 10 · 53%
80%
S&S designation survived the contest
ⓘ
Counts a Significant & Substantial citation as surviving when a settlement or judge's decision kept the designation, or the contest was dismissed or defaulted so the citation stands as issued. Vacated and withdrawn citations, and settlements that removed the designation, count against.of 5 decided S&S contests · industry: 79%
85%
Penalty reduction in decided contests
$86K proposed, $13K after decisions · industry: 39%
Source: MSHA Contested Violations file (public record), updated weekly. A dismissed or defaulted contest leaves the citation standing as issued; a vacated or withdrawn citation is removed from the violation record. Latest contest filed 2024-03-13. Vacated and withdrawn citations are removed from the file this view attributes through, so that outcome is slightly undercounted here.
Contested penalties
ⓘ
A reduction or dismissal at the Commission is a lawful outcome of contesting a proposed penalty. Figures are the proposed amount and the amount upheld in the docket's decision.Largest penalties this controller contested before the Federal Mine Safety and Health Review Commission, with the outcome on record.
| Docket | Decision | Judge | Year | Proposed / upheld |
|---|---|---|---|---|
| CENT 2024-0161 | Settlement | Sullivan | 2024 | $85K → $12K |
| WEST 2024-0159 | Dismissal | Simonton | 2024 | $2K → $2K |
Source: FMSHRC civil penalty dockets and decisions (public record), updated weekly.
Top causes
- HANDLING OF MATERIALS 4 non-fatal
- IGNITION OR EXPLOSION OF GAS OR DUST 3 non-fatal
- MACHINERY 1 non-fatal
- SLIP OR FALL OF PERSON 1 non-fatal
Incident timeline
2025
1
2023
6
2022
2
Operators under this controller
Mines on record
- Bainville MT
- Eaton Ranch ND
- Asgard Mobile Washplant ND
For insurers, brokers, and safety consultants
Where Pronghorn LLC; Isom Brothers Holding LLC stands on silica, penalties, and injury rate
MSHA's standard limits respirable silica to 50 micrograms per cubic metre, but MSHA publishes dust and quartz as separate files and never the silica figure itself. We derive it per sample, score it against the limit, and set the operator's injury rate against a benchmark built from the full MSHA operator record. With the 26-year penalty trail, contest posture, and fatality history. Delivered as a PDF with the underlying data as CSV.
The federal record itself stays free on this site. What costs money, and why.