A New Respirable Crystalline Silica Rule for the Construction, General Industry, and Maritime Sectors

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On March 25, 2016, OSHA issued a new Respirable Crystalline Silica Rule that will ultimately impact nearly one million workers in the construction, general industry, and maritime sectors. The Rule reduced the permissible exposure level (PEL) for respirable crystalline silica from 100 to 50 micrograms of silica per cubic meter of air (µg/m3) and established a new action level of 25 µg/m3. Other provisions were included to protect employees, such as requirements for exposure assessment, exposure control methods, respiratory protection, medical surveillance, hazard communication, and recordkeeping.

The Rule included two standards: one for construction (29 CFR 1926.1153) and one for general industry and maritime (29 CFR 1910.1053), both of which became effective on June 23, 2016. OSHA’s new Respirable Crystalline Silica Rule will be implemented over a period of five years (starting on the abovementioned effective date), with enforcement coming most quickly to the construction industry. OSHA has been enforcing the Respirable Crystalline Silica in Construction standard since September 23, 2017. However, for the first 30 days, OSHA offered compliance assistance in lieu of enforcement for those employers who were making good faith efforts to comply with the new construction standard. Effective October 23, 2017, OSHA commenced enforcement of all appropriate provisions of the Respirable Crystalline Silica in Construction standard, except for requirements for sample analysis,1 which will commence on June 23, 2018. OSHA will begin enforcing most provisions of the standard for general industry and maritime on June 23, 2018. This article provides an overview of OSHA’s Respirable Crystalline Silica Rule and its applicability to the construction, general industry, and maritime business sectors.


Crystalline silica is a basic component of soil, sand, granite, and many minerals. Quartz is the most common form of crystalline silica. Respirable size2 particles can be created as a result of activities such as cutting, drilling, and grinding of materials that contain crystalline silica. Crystalline silica has been classified as a human carcinogen. Silica exposure is a concern for nearly two million U.S. workers, including more than 100,000 workers in higher-risk jobs for this matter, such as abrasive blasting, foundry work, stonecutting, rock drilling, quarry work, and tunneling. Exposure to respirable crystalline silica can cause silicosis, lung cancer, and other respiratory and kidney diseases. There is no cure for silicosis, which in severe cases can lead to death in a few months.

OSHA has a newly established PEL (50 µg/m3), which is the maximum amount of crystalline silica to which workers may be exposed during an eight-hour work shift. OSHA also requires hazard communication training for workers exposed to crystalline silica, and a respirator protection program until engineering controls are implemented. OSHA estimates that more than 840,000 workers are exposed to silica levels that exceed the new PEL.

General industry sectors that will be affected by the new Rule include asphalt roofing materials, concrete products, cut stone, foundries, railroads, ready-mix concrete, shipyards, structure clay products, support activities for oil & gas operations, dental laboratories, jewelry, porcelain enameling, and pottery.

For construction, the most severe exposures generally occur during abrasive blasting with sand to remove paint and rust from bridges, tanks, concrete structures, and other surfaces. Other construction activities that may result in severe exposure include: jack hammering, rock/well drilling, concrete mixing, concrete drilling, brick and concrete block cutting and sawing, tuck pointing, tunneling, operating crushing machines, and milling.

Based on OSHA’s Respirable Crystalline Silica Rule, employers are required to:

  • Establish and implement a written exposure control plan that identifies tasks that involve exposure and methods used to protect workers, including procedures to restrict access to work areas where high exposures may occur.
  • Designate a competent person to implement the written exposure control plan.
  • Restrict housekeeping practices that expose workers to silica where feasible alternatives are available.
  • Offer medical exams including chest X-rays and lung function tests every three years for workers who are required by the standard to wear a respirator for 30 or more days per year.
  • Train workers on work operations that result in silica exposure and ways to limit exposure.
  • Keep records of workers’ silica exposure and medical exams.

OSHA provides a table that contains dust control methods for 18 common task groups for the construction industry. Employers can either use the control methods laid out by OSHA, or they can measure workers’ exposure to silica and independently decide which dust controls work best to limit exposures to the PEL in their workplaces. Employers who do not use OSHA’s recommended control methods must:

  • Measure the amount of silica that workers are exposed to if it may be at or above an action level of 25 μg/m3, averaged over an eight-hour day.
  • Protect workers from respirable crystalline silica exposures above the permissible exposure limit of 50 μg/m3, averaged over an eight-hour day.
  • Use dust controls to protect workers from silica exposures above the PEL.
  • Provide respirators to workers when dust controls cannot limit exposures to the PEL.

OSHA prepared the following flowcharts to provide assistance to employers that are working to comply with the new Respirable Crystalline Silica Rule. For more information regarding the enforcement guidance, please visit OSHA’s enforcement guidance for the Respirable Crystalline Silica standard for construction activities.

On December 19, 2017, OSHA released 18 fact sheets that provide guidance on the respirable crystalline silica standard for construction. These fact sheets provide employers with information on how to fully and properly implement controls, work practices, and, if needed, respiratory protection for each of the 18 task groups identified by OSHA.

The Mine Safety and Health Administration (MSHA) published its own proposed rule to address miners’ exposure to respirable crystalline silica. MSHA has mentioned that it had “looked at the OSHA Rule” to establish a new PEL for work activities subject to MSHA regulation. Please contact CEC’s Ali Lashgari (; 412-249-1558) with any questions or comments. CEC will make updates on respirable silica-related rules via this blog.

Note 1: Compliance Safety and Health Officers (CSHOs) should repeat Flowchart A for each employee engaged in a Table 1 task.

Note 2: To determine whether the engineering controls, work practices, and respiratory protection specified in Table 1 are fully and properly implemented, CSHOs should consult 29 CFR 1926.1153(c)(2), which contains additional requirements for tasks performed indoors or in an enclosed area, and for control measures involving wet methods or an enclosed cab or booth.

Note 3: Table 1 at 29 CFR 1926.1153(c)(1): Specified Exposure Control Methods When Working With Materials Containing Crystalline Silica

Note 4: Please click here to find details on each compliance guidance paragraph.


1 29 CFR 1926.1153(d)(2)(v)
2 Particles with a diameter equal or less than 10 μm

Reissued General Permit (PASPGP-4) Affects Linear Projects in Pennsylvania

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On July 1, 2011 the U.S. Army Corps of Engineers (Corps) issued the Pennsylvania Special Programmatic General Permit-4 (PASPGP-4) which replaces the expired PASPGP-3.  The PASPGP is a federal Clean Water Act, Section 404 permit which can be authorized by the Pennsylvania Department of Environmental Protection (DEP) and county conservation districts for minor activities in wetlands, streams, rivers, and other waters without additional review by the Corps.  For the most part, the PASPGP-4 is a continuation of the PASPGP-3 but there are some key changes that will impact linear projects.  Although the changes were mainly aimed at the rapidly growing natural gas industry in Pennsylvania, they will affect all linear projects ranging from sewer and water pipelines to electrical, cable, and telephone lines.  The changes affecting linear projects are summarized in this posting.

One aspect of the PASPGP-4 which was the focus of a lot of debate was the definition of Single and Complete Projects.  The definition of a single and complete linear project still refers to each crossing of a separate water body.  However, the PASPGP-4 makes a distinction between the overall project and a single and complete project.  The overall project includes all regulated activities that are reasonably related and necessary to accomplish the project purpose.  Applicants must supply the locations for the start and end points along with the proposed crossings and the total cumulative impacts needed to accomplish the overall project.  Therefore, although a linear project may contain more than one single and complete project, the total cumulative impacts needed to accomplish the overall project must be disclosed.  The cumulative impacts (meaning the sum total of all of the crossings) for the overall project will then be used to determine the category of activity.  Therefore, if the cumulative impact for the overall project is greater than 1 acre of jurisdictional waters or 250 linear feet of streams, then the overall project will be a Category III activity and will be reviewed by the Corps.  However, the cumulative impacts are only used to determine the category level of the activity.  They are not used to determine whether the project is eligible for authorization under the PASPGP-4.  The project will still be eligible under a PASPGP-4 as long as the impacts for each single crossing are less than 1 acre of jurisdictional waters or 250 linear feet of streams.  Therefore, this process has not changed.

The PASPGP-4 includes clarification on the calculation of linear footage of stream impact.  The linear footage of stream impact is now to be measured from the top of bank to the top of the opposite bank and from the upstream to downstream limits of work.  The linear footage of stream impact will be the greater of these two measurements.  Therefore, the right-of-way (ROW) will typically be used to determine the linear footage of stream impacts for pipeline projects.

Through the PASPGP-4, the Corps has established two triggers which can automatically push a project into a Category III review.  The first trigger involves threatened and endangered species.  If the PNDI for a project identifies a conflict with a federally listed species or includes avoidance measures from the U.S. Fish and Wildlife Service (USFWS), the project will be considered a Category III activity and must be reviewed by the Corps.  The second trigger involves interstate projects.  Projects which will be located in Pennsylvania and another state will also be considered a Category III activity and must be reviewed by the Corps.

There was one major change to the PASPGP-4 that was included in the draft version of the general permit that was not included in the final version.  The Corps was expected to lower activities authorized as Waiver 2 (25 PA Code § 105.12(a)(2) Waiver 2) from a Category III activity to a Category 1 activity.  Waiver 2 is for water obstructions in a stream or floodway with a drainage area of 100 acres or less.  This waiver applies only to the DEP and not to the Corps.  Since these activities are still Category III, they must be reviewed by the Corps to obtain federal authorization for the project.

Lastly, projects which were authorized by the PASPGP-3 have been reauthorized by the PASPGP-4 provided the permit for the project had not expired by June 30, 2011.  For most projects, the new expiration date for the reauthorized PASPGP-3 will be tied to any applicable PADEP Chapter 105 applications such as a General Permit or Joint Permit.

If you have any questions regarding the requirements of the PASPGP-4 or any other aspects of the permitting requirements for linear projects in Pennsylvania, please contact Paul Kanouff at or 800-899-3610.

Avoiding Failures and Performance Issues with Mechanically Stabilized Earth (MSE) Walls and Slopes

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Over the past 20 years, the use of mechanically stabilized earth (MSE) walls and slopes has become very common in a large number of construction applications in the U.S. and around the world.  The technology used to build these structures is really quite simple:  reinforcing, typically metal or synthetic grids or sheets, are layered in with compacted soils, adding shear strength and allowing the soils to stand at progressively steeper angles.  Wall faces are typically constructed using concrete panels, split-face masonry blocks, or even vegetation that primarily provides erosion control and aesthetics. The faces provide little if any structural support to the retained soils.

The relatively low cost of MSE structures have made them quite prevalent in transportation and site development projects, and have also led to their use for waste management and environmental remediation projects.  MSE walls can often be constructed for less than half the cost of comparable concrete or steel structures.  This cost advantage increases as the height of the structure increases. This reduced cost has enabled the development of increasingly marginal projects, and pushed the limits of the technology, literally, to new “heights”.  For example, several recent airport expansion projects in the U.S. have utilized MSE wall and slopes well in excess of 100 feet tall.

However, this lower cost and increased use of the technology has come at a price.  While there are no specific published numbers available, the failure rate of these structures has been estimated by some to be as high as 5% to 7%, with 2% likely being a low-end estimate.  “Failure” in this case encompasses not only large-scale collapse or movement, but also settlement and performance issues.  In any case, the number of MSE walls and slopes exhibiting problems is alarmingly high for an engineered structure, and the cost to repair these problems can be many times the original construction cost.

So why do these failures occur?  Over the past 10 years, CEC has been involved with the specification, design, construction monitoring, and failure investigation of a number of MSE walls and slopes.  Published evaluations on MSE wall failures are also quite numerous.  Many studies have shown that, particularly in the private site development sector, engineering site layout, surface and subsurface drainage features, geotechnical engineering evaluations, and construction monitoring are often inadequate.  CEC’s experience investigating failures has identified a number of construction errors that have led to performance issues.  One re-occurring construction factor leading to failure is inadequate backfill compaction when clayey soils are used in the wall construction.

The published studies and our experience also indicate that the contracting methods used for both design and construction of MSE walls and slopes may be contributing to the high failure rate.  Most MSE walls are designed and constructed using a design-build contract where the contractor provides the detailed wall design and constructs the wall.  This process results in highly competitive “cut-throat” bidding among vendors, encourages overly optimistic design assumptions, and often hampers communication and review by the design team.  This process often places numerous risks unknowingly back on the owner.

How can you protect yourself and reduce the risk of failure for MSE walls and slopes on your project?  First, hire civil and geotechnical engineers with experience in the investigation, design, and specification of these structures and ensure that their services are carried through into construction.  If a design-build process is used, a detailed wall layout and performance specification must be prepared listing all wall design, testing, and construction requirements.  Full-time, on-site construction monitoring should be provided by either the wall designer or geotechnical engineer to ensure that the proper testing and site inspections are done. The contractor should not provide the construction monitoring services.   Finally, hire a contractor with experience and certification in MSE construction.

If you have any questions about the use, specification, design, or construction of MSE wall and slopes and how they may impact an upcoming project, contact Douglas Clark, P.E. ( or Jeffrey Woodcock, P.E. ( at 800-365-2324.

Navigating Muddy Waters – New Effluent Limitation Guidelines Will Impact 21,000 Construction Sites Annually

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On November 23, 2009, EPA released the final Construction & Development Effluent Limit Guidelines (C&D ELG).  The final C&D ELG will impact all construction sites disturbing more than one acre by imposing non-numeric effluent limitations.  More importantly, the C&D ELG will impose numeric effluent limits for the first time on all construction disturbing more than 10 acres within approximately 4 years.  Most construction sites will need to use Passive Treatment Systems (PTS) to achieve those limits rather than the typical erosion and sediment control measures currently in use.  EPA estimates as many as 21,000 construction sites annually would need to meet those numeric limit standards.

In the past, sediment control practices have generally been designed based upon a rule of thumb.  Many states rely on 1800 ft3/acre of drainage (or disturbed acre), which doesn’t take into consideration the discharge quality.  In fact, a sediment control measure can have an 80% settling efficiency and still produce a turbid (muddy) discharge.  With this in mind, EPA has been struggling since early 2000 to establish a C&D ELG, with prodding from environmental groups.

In November 2008, EPA published a draft C&D ELG that set the ELG (turbidity) at 13 Nephelometric Turbidity Units (NTUs) for sites that disturbed 30 acres or more, were located in areas of the country with high rainfall intensity, and located on soils that had at least 10% clay.  That incredibly low turbidity limit (13 NTUs) severely limited the stormwater treatment options to Active Treatment Systems (ATS) that, simply put, look and function like small waste water treatment plants.  EPA requested public comment on the draft rule and requested additional data on the cost benefit analysis, treatment feasibility, and other components.  Concerns mounted as those affected began questioning the draft rule, particularly the feasibility of achieving the 13 NTU discharge standard.

EPA published the final C&D ELG in November 2009 with major revisions based on the comments received.  EPA chose to greatly simplify the rule and increase the numeric standard.  Below is a summary of the final rule:

  • All construction projects must install best practicable control technologies.
  • Sediment basins and other impoundments must be dewatered from the surface.
  • The ELG has been set at 280 NTUs.  This limit is a daily maximum average, based upon sampling for storms up to the 2 yr, 24 hr storm.  Discharges from storm events greater than the 2 yr, 24 hr are not required to meet the ELG.
  • Discharges from construction sites must meet an effluent limitation guideline as follows:
    • Within 18 months of the effective date of the rule (August 2011), sites disturbing 20 acres or more must meet the ELG.
    • Within 4 years of the effective date of the rule, sites disturbing 10 acres or more must meet the ELG.
    • For both scenarios above, the size limitations apply to “larger common plans of development” like subdivisions with multiple small lots.

Each state will need to marry the final C&D ELG with their existing monitoring plans, which will be a huge task.  Additionally, EPA has noted that as each state’s construction stormwater permit comes up for renewal, these requirements must be inserted.  EPA is the permitting authority in four states.  Their general permit is due to expire in June 2011 and will be reissued with the ELG requirements in it at that time.  Interestingly, North Carolina’s permit was in the midst of renewal when the ELG rule was finalized, and EPA only allowed their permit to be renewed for 18 months (through August 2011).  After that date, the reissued permit must include the ELG requirements.

As indicated earlier in this blog, PTS will generally be required to meet the numeric standard of 280 NTUs.  A PTS incorporates a flocculant with a standard construction site practice.  An example of a PTS is a jute-lined ditch that has been impregnated with polyacrylamide (PAM).   Design components that must be considered include mixing zones and settling zones.  At this point, we don’t have design tools that dictate the amount flocculant to be used on a site.  Flocculants and soils must be matched (not every flocculant works on every soil), and the applications tweaked in the field for peak performance.  Then the flocculant must be reapplied after rain events.

You can expect to have the ELG requirements inserted into the permit language if your state’s permit expires before August 2011.  If, however, your permit was reissued before the rule was finalized and without the ELG language in it, EPA could administratively open the permit to have the language inserted into it.  I suspect that between June 2011 (when EPA’s Construction General Stormwater permit expires) and August 2011 (the deadline to begin implementing the ELG) some permits may be administratively opened.  That option is certainly possible.

If you have any questions about the C&D ELG, how it may impact an upcoming project, and how you can meet the numeric standard, contact CEC’s Nashville office at (800) 763-2326.