How to Follow Table 1 When You Core or Grind Concrete

Why this matters

Table 1 of the construction silica standard is the cheapest way a small shop can do dusty concrete work legally, because it skips air monitoring entirely. The catch is in two words: the row has to be fully and properly implemented. A grinder shroud on a shop vacuum, a core drill whose water feed was turned down to keep the floor dry, or a broom at the end of the job each knock the task out of Table 1 and into exposure assessment, and none of them looks like a violation while you are doing it. This is the field procedure for getting a row right. What the standard requires and why lives in Respirable Crystalline Silica and the Construction Standard; this card is how you set up on the day.

Before you start: the slab or wall itself

Before any of the Table 1 steps, find out what is inside the concrete. A core bit or a rotary hammer that hits a post-tensioned tendon, a buried conduit, radiant heat tubing or a gas line creates a hazard far worse than the dust. Scan the area with a concrete scanner or have it scanned, check for post-tensioning stamps or notices in the garage or slab edge, and ask the owner about in-floor heat. If a post-tensioned slab is suspected, nobody drills or cores until the location is cleared by someone qualified to mark tendons. If the scan shows rebar at the planned spot, move the hole rather than cut through structural steel without the engineer's say-so.

The steps

1. Name the task and find its exact row. Table 1 rows are written by tool, not by job. A core drill on a rig or stand fed with water is the rig-mounted core saw or drill row. A rotary hammer or hand drill making anchor holes is the handheld and stand-mounted drill row. A grinder taking down a high spot is the handheld grinder row for uses other than mortar removal; tuckpointing is its own row with stricter respirator columns. Some rows are outdoor-only, such as the handheld saw row for fiber cement board. Skip this and you set up the right control for the wrong row, which is the same as setting up none.

2. Total the shift's Table 1 time before you pick a column. Add every Table 1 task this employee will do today, including tasks on other jobs. If the total exceeds 4 hours, each task takes its more-than-4-hours respirator column, per 1926.1153(c)(3). Skip this and the morning's 3-hour saw job and the afternoon's 2-hour core job each look like short tasks, and the respirator the combined day requires never comes out of the truck.

3. Set up the control the row names, to its numbers.

• Wet methods (saws, core rigs, some grinders). Water integrated at the bit or blade, at a flow rate sufficient to minimize the release of visible dust, per (c)(2). Use a tool designed for wet cutting, plugged into a GFCI-protected circuit, with the cord kept out of the slurry.
• Shroud and dust collector (grinders). A shroud made for the tool, and a dust collector providing at least 25 cubic feet per minute of airflow per inch of wheel diameter, with a filter of 99 percent or greater efficiency and a cyclonic pre-separator or filter-cleaning mechanism. A 5 inch wheel needs 125 cubic feet per minute or more. A vacuum's rated airflow is measured at the unit, and real airflow at the shroud drops with a long hose and a loading filter, so pick a unit with margin.
• Shroud or cowling (drills). A dust collection system per the tool manufacturer's instructions, with a filter of 99 percent or greater efficiency and a filter-cleaning mechanism, and a HEPA-filtered vacuum when cleaning the holes, never blowing them out.

Skip this and the task is no longer a Table 1 task, which means exposure assessment under 1926.1153(d).

4. Indoors, add exhaust and close the area. For indoor or enclosed work, (c)(2) requires exhaust as necessary to minimize the accumulation of visible airborne dust. A fan in a window exhausting outward, with the basement door shut and the family upstairs, covers most residential jobs. Restricting access is also part of the written plan. Skip this and dust that the shroud missed hangs in a small room for the rest of the job, and reaches people who are not wearing anything.

5. Put on the respirator the row assigns, under the program. Where the column calls for one, it is a respirator with at least the listed assigned protection factor, worn by someone medically cleared and fit tested under 29 CFR 1910.134, with a user seal check every time it goes on. See related: How to Do a User Seal Check Every Time. Hearing protection goes on at the same time; core rigs, rotary hammers and grinders are all loud enough to need it.

6. Run the first minute and watch the tool. Visible dust escaping at the shroud skirt, the core bit, or the drill tip means the control is not working. Stop, find the cause (hose off, filter loaded, water feed blocked, shroud skirt not flat to the surface), fix it, and restart. Skip this and you finish the task out of compliance and find out when you see the gray film on everything.

7. Clean up without making it airborne again. No dry sweeping or dry brushing, no compressed air to clean surfaces or clothing, per 1926.1153(f). HEPA-vacuum dry dust, and squeegee or wet-vacuum slurry before it dries into a powder. Wet concrete slurry is strongly alkaline and burns skin, so gloves stay on and splashes get rinsed with water. Empty the collector and change its filter outdoors, wearing the respirator, because the dust in the canister is the most concentrated on the job.

8. Write down what you did. Task, row, minutes, control, respirator if any, and the employee. This feeds the exposure control plan's annual review and the 30-day respirator count that triggers medical surveillance. See related: The Silica Exposure Control Plan SOP.

A worked example: a furnace vent through a basement wall

A tech is installing a high-efficiency furnace and needs a 3 inch hole through an 8 inch poured basement wall for the vent and combustion air pipes, plus four anchor holes in the slab for a pipe support. Earlier the same day he spent 1 hour on another job running a handheld saw with water outdoors. The card he fills in before he starts:

TABLE 1 PRE-TASK CARD              Job: furnace, bsmt
Scan:       rebar 6 in left of mark -> hole moved 4 in
Task A:     rig-mounted core drill, water
Task B:     rotary hammer, 4 anchor holes, shroud+vac
Where:      indoors, basement, door shut, fan out
Time today: saw 1.0 h + core 0.8 h + drill 0.2 h
            = 2.0 h, 4 h or less column
Respirator: none required by rows A or B
Collector:  99% filter, auto filter clean, HEPA
Cleanup:    wet vac slurry, HEPA vac, no broom

The coring. The rig is anchored to the wall, the water feed is opened before the bit touches concrete, and a wet vacuum sits under the cut to pick up slurry as it runs. In the first minute the slurry is running down the wall toward a duplex receptacle about 2 ft below. That is a stop: the tech unplugs the rig, moves the receptacle's circuit off by switching its breaker off and confirming the receptacle is dead with a tester proved on a known live source before and after, and sets a catch tray under the bit before restarting. The core takes 45 minutes of drilling, about 0.8 hours.

The anchor holes. The rotary hammer goes on with its shroud connected to the collector, and in the first hole the tech sees a puff at the tip. The hose had slipped off the shroud's port. He stops, reseats it, and the next three holes run clean. He vacuums each hole with the HEPA vacuum rather than blowing it out. Total drilling time, about 12 minutes, 0.2 hours.

The shift total. 1.0 hour plus 0.8 hour plus 0.2 hour is 2.0 hours, under the 4-hour line, so both rows stay in their 4-hours-or-less columns and neither row lists a respirator there. Had the morning saw job run 3.5 hours instead of 1, the total would be 3.5 plus 0.8 plus 0.2, which is 4.5 hours, and every task that day would take its more-than-4-hours column. Neither of these two rows lists a respirator in either column, but the morning saw work would.

Restoring the circuit. Before the breaker goes back on, the slurry is cleaned off the wall, the receptacle and its box are dry to the touch, and the tech stands to the side of the receptacle as the breaker closes, then tests that the receptacle's GFCI trips and resets.

How to verify you got it right

• No gray film beyond the work area. Wipe a dark cloth on a surface 6 ft from the cut. Dust there means the control or the exhaust leaked.
• The collector still pulls. A filter indicator in the red, or a shroud that will not hold to the surface by suction, means airflow has dropped below what the row assumed.
• The record matches the day. Task, row, minutes and the shift total are written down, and the respirator column used matches the total, not the single task.
• Nothing went airborne at cleanup. No broom or blowgun was used, and the canister was emptied outdoors.

References

• 29 CFR 1926.1153(c) and Table 1, (c)(2) and (c)(3) for exhaust, water flow and the 4-hour total; (f) for housekeeping.
• 29 CFR 1910.134, Respiratory Protection, for the program behind any respirator a row assigns.
• OSHA Small Entity Compliance Guide for the construction silica standard, for row-by-row equipment detail.
• See related: Respirable Crystalline Silica and the Construction Standard; Silica in Materials You Might Not Expect.
• See related: The Dusty Task Setup SOP; How to Measure Noise on Your Own Jobs.