Class Code 1741
Silica Grinding; Plaster Mills
Class Code 1741 applies to businesses that grind silica-containing materials and operate plaster mills — operations that generate significant respirable dust. The WCIRB pure premium rate for California effective September 1, 2026 is $4.364 per $100 of payroll. Understanding this classification helps employers control silica exposures, reduce claims, and assign payroll accurately for workers' comp.
What Class Code 1741 Covers
This classification covers plants and operations where crystalline silica is mechanically ground, milled, or pulverized and where plaster (gypsum) is processed in mill settings. Typical activities include grinding silica sand or silica-bearing aggregates in ball, hammer or roller mills; crushing, screening, classifying and bagging powdered plaster and sand; blending silica-containing additives into gypsum; and continuous millhouse operations with conveyors, hoppers, and dust collection systems. It includes both primary production (grinding) and downstream tasks in the same facility like packaging and loading when performed as part of the mill process. Note: some plaster mills primarily process gypsum, which is low in crystalline silica, but are still classed here when silica grinding or significant silica-containing additives occur.
Who It Applies To
- Silica sand grinding facilities and mineral processing mills
- Plaster (gypsum) mills that blend or grind silica-containing additives
- Mill operators, control-room technicians, and bagging/packaging staff
- Maintenance mechanics and millwrights servicing grinders and conveyors
- Forklift operators and bulk loaders handling ground product
Common Job Duties
- Operating and monitoring ball, hammer or roller mills and classifiers
- Feeding hoppers, conveyors, crushers and screens with raw material
- Bagging, palletizing and bulk loading powdered plaster or sand
- Routine maintenance: replacing liners, changing screens, greasing bearings
- Cleaning mill housings and dust collectors using HEPA vacuums or wet methods
- Sampling and quality-control testing of ground product in lab areas
- Operating dust collection systems, cyclones and baghouses
Common Injury Risks
Understanding the $4.364 Rate
The pure premium rate of $4.364 per $100 of payroll is the WCIRB-calculated expected claim cost before taxes, assessments, experience modification, and insurer adjustments. To estimate the pure premium, divide total payroll by 100 and multiply by 4.364. The actual premium you pay will also reflect your company’s experience modification, payroll audits, policy discounts, coverage deductibles, and any classification splits if employees perform multiple types of work.
Cal/OSHA Compliance Requirements
Cal/OSHA enforces the crystalline silica standard (Title 8, Section 1532.3) that requires exposure assessment, a written exposure control plan, engineering controls (water suppression, local exhaust ventilation), and respirator use when controls do not keep exposures below the PEL. Employers must provide training, medical surveillance for workers above the action level, fit testing for respirators, and use HEPA-filtered vacuums and wet methods for housekeeping rather than dry sweeping or compressed air.
How Key HR Helps Employers Under Class Code 1741
A PEO like Key HR can help employers in this class reduce workers' comp costs by ensuring accurate payroll classification, implementing silica-specific safety programs (written control plans, respiratory protection programs, and fit testing), and providing on-site or virtual safety audits and training. We also manage claims and return-to-work programs to improve experience modification rates — combining compliance support and claims handling to lower overall comp costs for grinding and plaster mill operations.
Get a QuoteFrequently Asked Questions
If my plaster mill mostly processes gypsum, does it still belong in Class Code 1741?
If the facility performs grinding or milling of silica-bearing materials or adds silica-containing additives, it should be classed under 1741. Pure gypsum mills with negligible silica exposure may warrant a different classification; a workplace exposure assessment and payroll breakdown will determine the correct code.
What practical steps reduce silica-related workers' comp claims in a grinding mill?
Key steps are engineering controls (water suppression, local exhaust and enclosures), effective dust collection with HEPA filtration, strict housekeeping with HEPA vacuums or wet methods, a written respiratory protection program and medical surveillance, plus hands-on training and PPE enforcement — these measures reduce exposures and follow-on compensable illnesses.
How does payroll get audited when workers perform both mill and non-mill tasks?
Insurers perform payroll audits and expect employers to allocate payroll to the appropriate class codes based on tasks performed. Maintain time records, job descriptions, and job cost reports so hours and wages can be split between codes; accurate allocation avoids overpaying or underpaying for the 1741 classification.
Quick Facts
- Class Code
- 1741
- Classification
- Silica Grinding; Plaster Mills
- Pure Premium Rate
- $4.364 / $100 payroll
- Effective Date
- September 1, 2026
- Source
- WCIRB Approved Filing
Manage Workers' Comp Through a PEO
Key HR provides pay-as-you-go workers' comp for California employers — no large deposits, no audits, better rates.
Get a Quoteor call (800) 922-4133Ready to Simplify Workers' Comp for Class Code 1741?
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