Non Table 1 Tasks – Construction
In Part 4, we took a look at Table 1 and looked at a couple of examples to show how to use it. It would be nice if all construction activities involving silica exposure were covered in Table 1. Truth is, they aren’t. Mixing, pouring, paving, finishing, and other non-removal type activities are not listed. So what do you do?
If you aren’t using Table 1 or can’t use Table 1, things get a bit more complicated. The short, simple answer is keep employee exposures below 50 micrograms. The long answer – read on.
Our Example from Last Time (Part 4) – with a twist
Let’s take another look at our first concrete pad removal example from last time. If you recall, you will be removing three sections of concrete in an outdoor parking lot with a jack-hammer. Each section will take about one hour of actual jack-hammering. You’ll be using a standard, air-driven jack-hammer. Only this time, you’ll be working outdoors in the winter, so a water spray is not feasible and you don’t have a dust collection system.
Question: What do you do?
Answer: Here’s where things get a bit more involved. Jack-hammering and power chipping is listed in Row 10 of Table 1. Since you are not using a water spray or a dust collector as listed in Column 2, you can’t use Table 1. If you can’t use Table 1, then you have to use the Alternate Exposure Control Methods (paragraph d of the OSHA Silica Standard).
Paragraph d outlines all the things you need to do if you can’t or aren’t using Table 1 and requires the following:
- Employee exposures to silica must remain below 50 micrograms (the Permissible Exposure Limit).
- Each employee with potential exposures above 25 micrograms (the Action Level) must be assessed for exposure. To do this, you must use previous air sampling results or conduct air sampling on the work they are currently doing. Either is acceptable.
- Engineering and work practice controls must be implemented to make sure employee exposure is below 50 micrograms. If this is not feasible, then implement what is feasible and employees also must wear respirators.
Another example – a task that’s not in Table 1
Two employees will be pouring foundations for several wood fence posts. To do this, they will add water to a 50-pound bag of cement, mix by hand, then shovel the mix into the hole. Each hole will take about 20 minutes.
Mixing cement is not in Table 1. Since you can’t use Table 1, you must do paragraph d of the Standard. Here is one possibility:
- Based on observations, you see that most of the dust generated is while the employees are opening the bag and dumping the bag. Once the cement is wet, there is little, if any, dust.
- If you have no air sampling data, you tell the employees to have a continuous mist of water on the bag while it’s being emptied to minimize dust (an engineering control). As additional protection, you might want your employees to wear a respirator while the bags are being emptied just as a precaution against a potential over-exposure.
- Since you have no air sampling data, you must conduct air sampling to ensure employee exposures are below the Permissible Exposure Limit.
- If air sampling results are below the Permissible Exposure Limit (50 micrograms), your employees can stop wearing a respirator. If air sampling results are also below the Action Level (25 micrograms), you don’t need to do any additional monitoring.
Use Table 1 whenever possible. If you can’t use Table 1, you’ve got some work to do.
Next: the Exposure Control Plan
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