Riverside Operation has $4K in proposed MSHA penalties and $0 outstanding across 2 contested dockets, plus health sampling and the full incident record.
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Fatalities
0
Total incidents
11
Years on record
1983–2026
Latest incident
Mar 2026
Compliance record
MSHA citations since 2000
31
citations
9
significant & substantial
$4,351
proposed penalties
$4,351
paid to date
100% of proposed penalties paid to date, a $0 gap.
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: 787 inspection hours is too few for a stable rate. A minimum of 1,000 inspection hours is required.
Source: MSHA inspections data, updated weekly.
Riverside Operation has $4K in proposed MSHA penalties and $0 outstanding across 2 contested dockets.
Penalty disposition
ⓘDifferences between proposed and paid penalties reflect both settlements and conference reductions and amounts still owed. Outstanding is the balance currently owed.
$4K
proposed penalties
$4K
current assessed
$4K
paid to date
$0
outstanding
30 assessments are final orders; 2 contested dockets.
Of $725 in penalties contested before the Commission, $725 was upheld in final decisions.
As of the most recent assessment on 2023-08-30.
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.
Source: MSHA violations gravity and negligence coding, 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.
4citations taken to the federal commission · 13% of citations on record
Settled
4 · 100%
100%
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 Vacated and withdrawn citations, and settlements that removed the designation, count against.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 1 decided S&S contests · industry: 79%
0%
Penalty reduction in decided contests
$725 proposed, $725 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 2008-01-16.
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 mine contested before the Federal Mine Safety and Health Review Commission, with the outcome on record.
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: 2025-11-05
20%
of limit-tested samples over the exposure limit
29
samples
5
limit-tested
Most sampled contaminants
Quartz, respirable, >1% Qtz51 over
Respirable dust, <.1mg24
Show the individual readings (29)
Date
Contaminant
Concentration
Limit
Conc / limit
Occupation
2002-01-03
Quartz, respirable, >1% Qtz
0.25
0.16
1.56
Flotation/Concentrator Oper.
2025-11-05
Respirable dust, <.1mg
0
Hammer Mill Operator
2023-08-30
Respirable dust, <.1mg
0
Ball Mill Operator
2021-01-20
Respirable dust, <.1mg
0
Mechanic
2021-01-20
Respirable dust, <.1mg
0
Ball Mill Operator
2020-05-19
Respirable dust, <.1mg
0
Mechanic
2020-05-19
Respirable dust, <.1mg
0
Ball Mill Operator
2019-04-16
Respirable dust, <.1mg
0
Crusher Oper/Worker
2018-04-26
Respirable dust, <.1mg
0
Mechanic
2018-04-26
Respirable dust, <.1mg
0
Ball Mill Operator
2015-10-29
Respirable dust, <.1mg
0
Mechanic
2015-10-29
Respirable dust, <.1mg
0
Building Repair/Maint.
2013-02-26
Respirable dust, <.1mg
0
Ball Mill Operator
2013-02-26
Respirable dust, <.1mg
0
Ball Mill Operator
2010-09-29
Respirable dust, <.1mg
0
Utility Man
2009-02-18
Respirable dust, <.1mg
0
Utility Man
2009-02-18
Quartz, respirable, >1% Qtz
0.17
0.39
0.44
Ball Mill Operator
2009-02-18
Respirable dust, <.1mg
0
Supervisor, Co. Official
2005-05-04
Quartz, respirable, >1% Qtz
0.15
0.88
0.17
Ball Mill Operator
2005-05-04
Quartz, respirable, >1% Qtz
0.21
0.33
0.64
Mechanic
2004-10-26
Respirable dust, <.1mg
0
Mechanic
2004-10-26
Respirable dust, <.1mg
0
Flotation/Concentrator Oper.
2004-04-06
Respirable dust, <.1mg
0
Ball Mill Operator
2004-04-06
Respirable dust, <.1mg
0
Laborer, Bullgang
2003-12-23
Respirable dust, <.1mg
0
Laborer, Bullgang
2003-12-23
Respirable dust, <.1mg
0
Ball Mill Operator
2003-04-15
Respirable dust, <.1mg
0
Flotation/Concentrator Oper.
2003-01-02
Respirable dust, <.1mg
0
Flotation/Concentrator Oper.
2002-04-02
Quartz, respirable, >1% Qtz
0.14
0.61
0.23
Flotation/Concentrator Oper.
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.
Source: MSHA controller and operator history, updated weekly.
Workforce and production
Year
Employees
2026
4
2025
4
2024
4
2023
4
2022
4
2021
4
2020
3
2019
4
2018
3
2017
4
2016
5
2015
6
2014
5
2013
5
2012
4
2011
5
2010
4
2009
4
2008
4
2007
4
2006
4
2005
4
2004
5
2003
4
2002
3
2001
4
2000
5
Source: MSHA quarterly employment and production, updated weekly.
Riverside Operation sits in Riverside County, California, where the Census mining category is 0.1% of county employment.
Local economic context
ⓘCounty figures come from the US Census Bureau's American Community Survey, 5-year pooled estimates, so the 2023 vintage covers 2019 through 2023. The Census category is 'mining, quarrying, and oil and gas extraction', which is broader than MSHA jurisdiction and includes oil and gas workers no mine employs. These figures describe the surrounding county, not this mine, and are not a factor in any specific incident.
Riverside County, California · Population 2,449,909
0.1%
Mining share of county employment
$89,672
Median household income
Source: US Census Bureau, American Community Survey 2023 5-year estimates.
Quarterly safety rates
ⓘCitations per million reported employee-hours. Rates begin in 2000, when MSHA's quarterly employment data starts; earlier incidents are counted but cannot be rate-adjusted. Quarters under 100,000 reported hours are greyed: too few hours for a stable rate.
Citations per million employee-hours, as reported to MSHA
Quarter
Hours worked
Citations
S&S
Per 1M hrs
2026 Q2
1,725
0
0
0.0
2026 Q1
1,637
0
0
0.0
2025 Q4
1,607
0
0
0.0
2025 Q3
1,725
0
0
0.0
2025 Q2
1,963
0
0
0.0
2025 Q1
1,692
0
0
0.0
2024 Q4
1,598
0
0
0.0
2024 Q3
1,668
0
0
0.0
Show 98 earlier quartersHide earlier quarters
Quarter
Hours worked
Citations
S&S
Per 1M hrs
2024 Q2
1,661
0
0
0.0
2024 Q1
1,892
0
0
0.0
2023 Q4
1,511
0
0
0.0
2023 Q3
1,482
1
0
674.8
2023 Q2
1,834
0
0
0.0
2023 Q1
1,672
0
0
0.0
2022 Q4
1,602
0
0
0.0
2022 Q3
1,336
0
0
0.0
2022 Q2
1,396
0
0
0.0
2022 Q1
1,158
0
0
0.0
2021 Q4
1,265
0
0
0.0
2021 Q3
1,299
0
0
0.0
2021 Q2
1,214
0
0
0.0
2021 Q1
1,286
0
0
0.0
2020 Q4
1,249
0
0
0.0
2020 Q3
1,112
0
0
0.0
2020 Q2
1,429
0
0
0.0
2020 Q1
1,431
0
0
0.0
2019 Q4
1,485
0
0
0.0
2019 Q3
1,678
0
0
0.0
2019 Q2
1,705
0
0
0.0
2019 Q1
2,147
0
0
0.0
2018 Q4
2,008
0
0
0.0
2018 Q3
2,095
0
0
0.0
2018 Q2
1,648
0
0
0.0
2018 Q1
1,523
0
0
0.0
2017 Q4
1,404
0
0
0.0
2017 Q3
1,122
0
0
0.0
2017 Q2
1,378
0
0
0.0
2017 Q1
1,559
0
0
0.0
2016 Q4
1,488
0
0
0.0
2016 Q3
1,893
0
0
0.0
2016 Q2
1,947
0
0
0.0
2016 Q1
2,211
0
0
0.0
2015 Q4
2,493
1
0
401.1
2015 Q3
2,647
1
0
377.8
2015 Q2
2,391
0
0
0.0
2015 Q1
2,346
0
0
0.0
2014 Q4
2,479
0
0
0.0
2014 Q3
2,848
0
0
0.0
2014 Q2
2,801
0
0
0.0
2014 Q1
2,479
0
0
0.0
2013 Q4
2,360
0
0
0.0
2013 Q3
2,533
0
0
0.0
2013 Q2
2,735
0
0
0.0
2013 Q1
2,320
1
0
431.0
2012 Q4
2,422
0
0
0.0
2012 Q3
2,709
0
0
0.0
2012 Q2
3,221
0
0
0.0
2012 Q1
2,730
2
1
732.6
2011 Q4
2,211
0
0
0.0
2011 Q3
2,595
0
0
0.0
2011 Q2
2,737
0
0
0.0
2011 Q1
2,486
0
0
0.0
2010 Q4
2,355
0
0
0.0
2010 Q3
2,341
0
0
0.0
2010 Q2
2,341
0
0
0.0
2010 Q1
2,516
0
0
0.0
2009 Q4
1,993
1
1
501.8
2009 Q3
2,092
0
0
0.0
2009 Q2
1,877
1
0
532.8
2009 Q1
2,282
4
1
1752.8
2008 Q4
2,338
0
0
0.0
2008 Q3
2,300
0
0
0.0
2008 Q2
2,567
1
1
389.6
2008 Q1
2,084
0
0
0.0
2007 Q4
1,968
4
1
2032.5
2007 Q3
2,066
0
0
0.0
2007 Q2
2,070
0
0
0.0
2007 Q1
1,979
0
0
0.0
2006 Q4
2,004
0
0
0.0
2006 Q3
2,085
0
0
0.0
2006 Q2
2,384
1
0
419.5
2006 Q1
2,498
0
0
0.0
2005 Q4
1,803
0
0
0.0
2005 Q3
1,814
0
0
0.0
2005 Q2
2,492
0
0
0.0
2005 Q1
2,185
0
0
0.0
2004 Q4
2,295
1
1
435.7
2004 Q3
2,613
0
0
0.0
2004 Q2
2,526
0
0
0.0
2004 Q1
1,863
0
0
0.0
2003 Q4
1,701
1
0
587.9
2003 Q3
2,119
0
0
0.0
2003 Q2
2,320
2
0
862.1
2003 Q1
1,876
0
0
0.0
2002 Q4
1,814
2
1
1102.5
2002 Q3
1,766
0
0
0.0
2002 Q2
1,618
0
0
0.0
2002 Q1
1,665
2
0
1201.2
2001 Q4
1,636
0
0
0.0
2001 Q3
1,834
0
0
0.0
2001 Q2
2,338
2
1
855.4
2001 Q1
2,382
0
0
0.0
2000 Q4
2,197
0
0
0.0
2000 Q3
2,693
0
0
0.0
2000 Q2
3,304
0
0
0.0
2000 Q1
2,663
1
0
375.5
No fatalities recorded at this mine.
Reportable incidents
11 on file
2026 · 1 incident
March 19, 2026CA · Metal/Non-Metalmaintenance man, mechanic, repair/serviceman, boilermaker, fueler, tire tech, field service techHANDLING OF MATERIALS
The employee was welding a portable hopper in the warehouse and took off their welding helmet to grind. They put on their face shield but not their hard hat and after grinding, stood up, striking their head on the leg stand of the hopper cutting their forehead.
2011 · 2 incidents
September 14, 2011CA · Metal/Non-Metalledgeman/hand, quarry manDUST DISEASE OF LUNGS
Premier Silica LLC · Inhalation of radiations, caustics, toxic and noxious substances
On the above date the miner was confirmed to have silicosis by medical professional.
February 7, 2011CA · Metal/Non-Metalmaintenance man, mechanic, repair/serviceman, boilermaker, fueler, tire tech, field service techHANDTOOLS (NONPOWERED)
On 3/28/2011, employee reported to his supervisor that he had an accident on 2/7/2011. Employee stated that he fell against hand rail while trying to loosen bin indicator with tool/cheater bar. Employee stated that he injured right shoulder when he fell against handrail. Accident under investigation at this time with insurance carrier.
1996 · 2 incidents
October 22, 1996CA · Metal/Non-Metalwarehouseman, bagger, palletizer/stacker, store keeper, packager, fabricator, cleaning plant operatorMACHINERY
Premier Silica LLC · Caught in, under or between a moving and a stationary object
WHILE POSITIONING THE HOIST HE WAS HOLDING THE CHAIN AND ACCIDENTLY PUSHED THE UP BUTTON. THIS CAUSED HIS FINGER TO BE PULLED INTO THE CHAIN GUIDE.
August 24, 1996CA · Metal/Non-Metalwarehouseman, bagger, palletizer/stacker, store keeper, packager, fabricator, cleaning plant operatorHANDTOOLS (NONPOWERED)
HE WAS HOLDING A PANEL OF MATERIAL STEADY WHILE HELP GOT INTO POSTION TO HOIST THE PANEL. THE PANEL SLIPPED AND FELL AND LANDED ON HIS LEFT FOOT BEHIND THE SAFTEY TOE OF HIS BOOT.
1985 · 1 incident
May 22, 1985CA · Metal/Non-Metalmaintenance man, mechanic, repair/serviceman, boilermaker, fueler, tire tech, field service techSLIP OR FALL OF PERSON
WELDING NEW PLATES IN AIR SEPARATOR INNER CONE AND RECXEIVED FLASHBURNS TO BOTH EYES FROM TGHE ARC WELDER
June 20, 1984CA · Metal/Non-Metalwarehouseman, bagger, palletizer/stacker, store keeper, packager, fabricator, cleaning plant operatorSTEPPING OR KNEELING ON OBJECT
HE WAS PUSHING A STEEL LINER PLATE INTO PLACE WHEN HIS FOOT SLIPPED ON A BOLT, CAUSING HIM TO FALL THRU THE MILL DOOR OPENING. THIS RESULTED IN FRACTURING HIS LEFT 9TH RIB.
1983 · 1 incident
May 11, 1983CA · Metal/Non-Metalmaintenance man, mechanic, repair/serviceman, boilermaker, fueler, tire tech, field service techPOWERED HAULAGE
Premier Silica LLC · Caught in, under or between (Not Elsewhere Classified)
VACUUM HOSE CAUGHT BETWEEN PULLEY AND BELT WHICH HE PULLED OUT HE THEN PROCEDED TO DO IT AGAIN BUT THIS TIME PULLEY CAUGHT LEFT HAND BETWEEN BELT AND PULLEY THIS STOPPED THE MOTION OF THE BE BELT IT TRAPPED HIS HAND CHIPPED A BONE IN LEFT WRIST AND CONTUSIONS TO LEFT ELBOW