employee use a handheld grinder outdoors on a concrete wall for three
hours and then use a chipping hammer for two additional hours, the
employer would not be required to ensure that his employee uses a
respirator for the three hours the employee is using the grinder, since
respiratory protection is not specified on Table 1 for the use of a
grinder outdoors for more than four hours per shift; however, the
employer would be required to ensure that his employee uses a
respirator with an APF of 10 for the two hours the employee is using
the chipping hammer. This is so even though use of the chipping hammer,
if performed with no grinding beforehand, would not have required a
respirator for the duration that the tool was used. If the employee
will be engaged in two activities that both have ``None'' specified for
respiratory protection in both the ``<= 4hr/shift'' and the ``> 4 hr/
shift'' columns, such as driving a half-lane milling machine and then
operating a walk-behind milling machine equipped with an integrated
water delivery system, then respirator use would not be required for
any part of an employee's shift even if the employer knows that the
cumulative total of that work will exceed four hours.
    When an employee performs multiple tasks that do not exceed a
combined total of more than four hours, employers must provide the
respiratory protection specified in the ``<= 4 hr/shift'' column of
Table 1 for each task. For example, if an employer plans to have his
employee use a handheld grinder for mortar removal for one hour and a
stationary masonry saw for an

additional two hours, the employer is required to ensure that his
employee uses a respirator with an APF of 10 for the one hour the
employee is using the grinder. The employer would not be required to
ensure that his employee uses a respirator for the two hours the
employee is using the stationary masonry saw, since respiratory
protection is not specified on Table 1 for the use of a stationary
masonry saw.
    Thus, whatever permutations may arise, the employer must estimate
the duration of the task(s) to determine whether Table 1 will trigger
the requirement for respiratory protection. If unforeseen conditions
arise that cause the estimated duration to be revised for any of the
tasks, the employer is required to provide the required respiratory
protection as soon as it becomes evident that the employee will be
engaged in the task for more than four hours during the shift.
    Updating Table 1. Commenters, including LHSFNA, BAC, BCTD, Charles
Gordon, and James Hardie Building Products, Inc., suggested that the
utility of Table 1 will diminish over time if OSHA has no mechanism to
include new control methods that may be developed (e.g., Document ID
4207, pp. 2-3; 4219, pp. 20-21; 4223, pp. 98-102; 3588, Tr. 3792-3793;
2322, pp. 21-23).
    Commenters also provided specific recommendations for the frequency
at which OSHA should update Table 1 and the process by which OSHA
should do so. James Hardie Building Products, Inc. commented that
additional controls demonstrated to maintain or increase employee
protection should be incorporated by reference whenever they become
available ``without the need to undergo a formal rulemaking process''
(Document ID 2322, pp. 21-22). The National Consumers League and the
American Public Health Association suggested that OSHA consider
updating Table 1 periodically (e.g., every five years) and publish a
direct final rule to adopt a revised Table 1 when NIOSH deemed new dust
control technology effective and feasible (Document ID 2373, p. 3;
2178, p. 3). Similarly, the Center for Effective Government urged OSHA
to review Table 1 every five years and make revisions when new control
technologies are found to be technologically and economically feasible
(Document ID 3586, Tr. 3319).
    Other commenters urged OSHA to consider mechanisms to update Table
1 without going through the rulemaking process. NIOSH suggested that
the Agency develop a database of control technologies to supplement
those on Table 1, rather than initiate rulemaking to update Table 1
(Document ID 2177, Attachment B, pp. 20-21). LHSFNA suggested that OSHA
post enforcement decisions based on objective data online and permit
employers performing similar tasks to use the controls specified in
those decisions to meet their obligations under Table 1 (Document ID
4207, pp. 2-3). Holes Incorporated argued that Table 1 should be
amendable by employers when testing proves that using such controls
would ensure compliance with the PEL (Document ID 3441, p. 12; 3580,
Tr. 1491).
    IUOE, BCTD, and BAC argued that Table 1 should be an appendix to
the rule so that it can be more easily updated (Document ID 2262, pp.
48-49; 2329, p. 6; 2371, Attachment 1, pp. 30-31). BCTD offered an
approach for updating Table 1 that relied on the Agency establishing a
mechanism for employers, equipment manufacturers, and others to submit
data to the Agency for evaluation and subsequent inclusion in future
versions of Table 1. BCTD proposed:

    OSHA could publish the criteria in a non-mandatory appendix to
the standard, so employers, manufacturers and researchers would have
a clear understanding of what they will have to demonstrate to get
their proposed controls onto the table.
    Interested parties could then request that OSHA evaluate a
control option, supporting their request with objective data, peer-
reviewed studies, reports by NIOSH or other governmental agencies,
or other reputable sources. If OSHA determined, based on the
supporting data, that the technology meets its criteria for
inclusion on Table 1, OSHA would issue an interpretative letter to
that effect and/or issue a compliance directive advising its
compliance officers that employers that fully and properly implement
the particular control should be treated as if they were in
compliance with the requirements of Table 1. This approach would
enable OSHA to continually add to the options employers can utilize
as new technologies come on-line, while at the same time ensuring
that these additional controls meet the Agency's criteria (Document
ID 4223, p. 100).

    Charles Gordon also provided a detailed suggestion for the addition
of regulatory text to address the issue of updating Table 1:

    Updating controls. (i) Three years from the effective date of
this standard and every 3 years thereafter, OSHA shall request
comments on new or improved engineering controls which can achieve
the PEL or Action Level without supplementary respirator use for
operations specified in Table 1 or other operations not in Table 1
that have crystalline silica exposure over the Action Level.
    (ii) If OSHA concludes that a new control will achieve the PEL
without supplementary respirator use, it shall publish a notice
permitting that control to be used for that Table 1 operation along
with the other permitted controls or publish a direct final rule
including that other operation in Table I and permitting the use of
that control.
    (iii) If a commenter submits to OSHA an engineering control for
an operation in Table 1, which can achieve the action level without
supplementary respirator use based on valid studies and cost data
showing it is feasible, then no later than the date specified in
paragraph (f)(6)(i), OSHA shall publish a proposal, proposing that
that engineering control be the required engineering control for
that operation (Document ID 4236, Appendix 1, p. 1).

    Based on the comments and perspective reflected in the rulemaking
record, OSHA sees the value in periodically updating Table 1 and is
concerned that a static Table 1 may discourage innovation in the
development of control technologies for reducing silica exposure.
However, while OSHA may certainly consider future updates or
adjustments to Table 1 if warranted, it will likely need to accomplish
substantive changes through additional rulemaking. In any event, it has
no intention to bind a future Administration to such rulemaking,
whether to update Table 1 in particular or the entire rule in general,
according to a schedule built into this rule. Meanwhile, the need to
revise Table 1 in the future should be limited since the controls
specified--primarily wetting the dust or ventilating and collecting the
dust--are stated in general terms that will not be rendered obsolete
by, for example, design improvements to water spraying or vacuuming
equipment.
    Even if the proposed mechanisms are consistent with the law
governing rulemaking, OSHA is unwilling to specify a mechanism for
updating Table 1 for several reasons. First, the procedures outlined by
BCTD and Charles Gordon would commit the Agency to spend future
resources to accept a large volume of information from interested
parties, evaluate it in a timely manner, and prepare the needed
economic and technological feasibility analysis and other rulemaking
documents. OSHA may have higher rulemaking priorities and demands on
its resources at that time, however. Second, Table 1 cannot both
contain enforceable means of compliance and also be contained in a non-
mandatory appendix. To ensure that employers who do not conduct
exposure monitoring comply fully with the Table 1 provisions, OSHA must
include the control specifications of Table 1 in the final standard for
construction as requirements rather than as non-mandatory
recommendations. Third, the

controls specified on Table 1 are flexible and not tied to existing
technology. The controls specified on Table 1 provide for the use of
wet methods, ventilation, and in some cases, isolation. OSHA did not
provide specific criteria for ventilation systems (size, air flow rate,
etc.) or water flow rates. Instead, OSHA specifies that employers must
operate the tools with integrated dust controls in accordance with the
manufacturer's instructions. These instructions provide flexibility to
take advantage of advances in technology. For example, as manufacturers
develop effective surfactants to be used with water to further reduce
silica exposure, there will be no need for OSHA to update Table 1 to
specifically allow employers to use them. The requirement to use wet
methods would still be satisfied.
    Thus, OSHA rejects the suggestions to establish a specific
mechanism for updating Table 1 in the future. If significant
technological advances occur that require OSHA to initiate rulemaking
in order to incorporate emerging technology not already encompassed by
this rule, it will do so in the context of its rulemaking priorities at
that time. Of course, interested parties may petition the Agency at any
time to modify the dust control specifications on Table 1 of the
standard for construction, and OSHA will consider such petitions based
on the likely benefit that will accrue to workers and the Agency's
available resources at the time.
    Comparison with consensus standards. The requirements in paragraph
(c) of the standard for construction are generally consistent with ASTM
E 2625-09, the national consensus standard for controlling occupational
exposure to respirable crystalline silica in construction. The ASTM
standard provides a task-based control strategy, including five tables
that specify control measures and respiratory protection for common
construction equipment and tasks. While the ASTM standard provides this
task-based control strategy, it also applies the PEL and exposure
assessment to these tasks, as OSHA did in its proposal. However, OSHA's
final standard for construction, as discussed above, takes a different
approach by requiring specific engineering controls, work practices,
and respiratory protection for construction tasks on Table 1; where
employers fully and properly implement the engineering controls, work
practices, and respiratory protection specified on Table 1, compliance
with Table 1 is in lieu of the performance-oriented approach involving
a PEL and exposure assessment, as provided as an alternative exposure
control method in paragraph (d) of the standard for construction.
Additionally, there are numerous differences between the tasks listed
and the engineering controls, work practices, and respiratory
protection specified on OSHA's Table 1 and those included on ASTM's
tables. The ASTM standard also does not divide tasks according to
duration and does not apply the approach to tasks limited to 90 minutes
total time. The differences between OSHA's standard and the consensus
standard, including those in the overall approach to compliance and in
the format of Table 1, the tasks listed, and the engineering controls,
work practices, and respiratory protection specified, best reflect the
evidence received into the rulemaking record and the realities of the
construction industry. These differences will also enhance compliance
with OSHA's standard in the construction industry and, in doing so,
better effectuate the purposes of the OSH Act and protect employees in
the construction industry from the significant risks posed by exposures
to respirable crystalline silica.
    Table 1 entries. Table 1 identifies 18 common construction
equipment/tasks known to generate high exposures to respirable
crystalline silica. For each kind of equipment/task identified, Table 1
specifies appropriate and effective engineering controls, work
practices, and, when necessary, respiratory protection. As proposed,
Table 1 listed 13 construction operations that expose employees to
respirable crystalline silica and identified control strategies and
respiratory protection that reduce those exposures. OSHA received many
specific comments about particular entries on Table 1 and on the
specified engineering controls, work practices, and respiratory
protection included for each entry. The additional equipment/tasks
included on Table 1 of the final rule for construction are handheld
power saws for cutting fiber-cement board (with blade diameter of 8
inches or less) and rig-mounted core saws and drills. Other entries on
Table 1 of the final standard for construction were broken out from
those proposed and added as separate entries. These include dowel
drilling rigs for concrete (included under ``Operating Vehicle-Mounted
Drilling Rigs for Concrete'' on proposed Table 1), walk-behind milling
machines and floor grinders (included under ``Milling'' on proposed
Table 1), small drivable milling machines (included under ``Milling''
on proposed Table 1), large drivable milling machines (included under
``Milling'' on proposed Table 1), heavy equipment and utility vehicles
used to abrade or fracture silica-containing materials or used during
demolition activities involving silica-containing materials (included
under ``Heavy Equipment During Earthmoving'' on proposed Table 1), and
heavy equipment and utility vehicles for tasks such as grading and
excavating, but not demolishing, abrading, or fracturing silica-
containing materials (included under ``Heavy Equipment During
Earthmoving'' on proposed Table 1). One entry on Table 1 of the final
standard for construction, vehicle-mounted drilling rigs for rock and
concrete, is the result of combining two entries from proposed Table 1
(``Operating Vehicle-Mounted Drilling Rigs for Rock'' and ``Operating
Vehicle-Mounted Drilling Rigs for Concrete''). One proposed entry,
``Drywall Finishing,'' was not included on Table 1 of the final
standard for construction. A discussion of each of the 18 Table 1
entries in the construction standard, including the comments received
and the changes made from the proposed Table 1 entries, follows below
in the order in which they appear on Table 1.
    Stationary masonry saws. Stationary masonry saws are used in the
construction industry to cut silica-containing masonry materials such
as bricks, concrete blocks, stone, and tile (see Section 5.7 of Chapter
IV of the FEA). They are mounted either on a table-top or a stand, and
include a flat platform where the work piece (e.g., a brick) sits
before the worker brings a rotating circular abrasive blade into
contact with the work piece by either pressing a swing arm mounted
blade onto the piece or by moving the piece on a sliding platform into
contact with a fixed blade (Document ID 4073, Attachment 4a, Rows 42-
48, 55-63, 179-188, 288-297, 343-351). The cutting surface is about
waist-high and at arm's length from the worker's breathing zone. A
nozzle for spraying water is usually attached near the blade, and is
connected to a water basin of some kind via a hose.
    When using stationary masonry saws, paragraph (c)(1)(i) of the
standard for construction requires that saws be equipped with an
integrated water delivery system that continuously feeds water to the
blade and that the tool be operated and maintained in accordance with
manufacturer's instructions to minimize dust emissions. Saw designs
vary between manufacturers and, as with other operating parameters,
manufacturer's recommendations for optimizing wet methods are likely to
vary somewhat with the saw size and

design. OSHA is not specifying a minimum flow rate; based on the
evidence in the record, OSHA anticipates that the water flow rate
specified by the manufacturer will optimize dust reduction. OSHA
recognizes that the employer's best available information for reducing
dust with a specific control comes from the manufacturer's operating
instructions. This is why OSHA is requiring the saw be operated and
maintained according to the manufacturer's instruction to minimize
dust.
    The language describing the required control for stationary masonry
saws was revised from the proposed rule to clarify that water must be
continuously applied to the blade, and language was added to require
that manufacturer's instructions be followed. This reflects OSHA's
intent that employers use a saw with integrated water delivery system
supplied by the saw manufacturer. OSHA finds that systems that are
developed in conjunction with the tool are more likely to control dust
emission effectively by applying water at the appropriate dust emission
points based on tool configuration, and not interfere with other tool
components or safety devices. These include free-flowing water systems,
with or without a pump and basin, that are designed for blade cooling,
as well as manufacturer systems designed for dust suppression alone
(Document ID 1555, p. 509; 3998, Attachment 12a, pp. 9, 15-16; 3998,
Attachment 12e, p. 3).
    The proposed entry for stationary masonry saws also included a note
requiring that water be changed frequently to avoid silt build-up in
water and that the blade not be excessively worn. CISC commented that
terms such as these were too ambiguous and would thus prevent the table
from being a realistic compliance option (Document 2319, p. 98). OSHA
understands that these notes could be subject to interpretation and in
response, has removed the notes from Table 1. However, these practices
are often included in manufacturer's instructions, and OSHA considers
these type of instructions to be part of fully and properly
implementing engineering controls (e.g., Document ID 4073, Attachment
4a, Rows 59-61).
    In the FEA, OSHA's exposure profile for stationary masonry saws
shows that wet cutting is an effective dust control. The median 8-hour
TWA exposure in the profile is 34 [mu]g/m\3\ for workers using saws
with water delivery systems (Table IV-5.7-B in Section 5.7 of Chapter
IV of the FEA) and the mean exposure for wet cutting is 41 [mu]g/m\3\,
substantially lower than the mean of 329 [mu]g/m\3\ for dry cutting
operations, a disparity that affirms that use of water on stationary
saws significantly reduces exposure to respirable crystalline silica.
Additional field data also show the effectiveness of water to control
respirable crystalline silica exposures during cutting. Flanagan et
al., in their 2006 study and 2009 data set, found that wet cutting
methods (details not available) were associated with markedly lower
exposure levels than were reported for all workers using table-mounted
saws (Document ID 0677; 0677, Attachment 2). The silica concentrations
reported by Flanagan et al. over the sampling period (ranging from 12
to 505 minutes) when wet cutting ranged from 6 [mu]g/m\3\ to 316 [mu]g/
m\3\, with a mean of 73 [mu]g/m\3\ and median of 46 [mu]g/m\3\
(Document ID 0677; 0677, Attachment 2). Since most of the sample
durations in this dataset were less than 360 minutes, workers' 8-hour
TWA exposures were even lower. These data also included indoor work.
    In addition to these field results, the record includes
experimental studies that examined the effectiveness of wet dust
control systems. Meeker et al. (2009) compared intensive masonry
cutting done without controls to exposures while using saws with
integrated water delivery systems and maximum flow rates of 2.3 and 2.4
liters per minute (0.6 and 0.63 gallons per minute) and found that wet
saws were associated with a 91 percent reduction in exposure to
respirable quartz (Document ID 803, p. 1; 2177, Reference 11, pp. 104,
107-108). Carlo et al. (2010) found reduction rates of 99 percent in
the respirable dust exposure when water was applied at the
manufacturer-recommended water flow rate, compared to dry cutting
(Document ID 3612, pp. 246-247, 249). While respirable dust reductions
do not always translate to exactly the same percent reduction in
respirable silica levels, OSHA finds that respirable dust reductions
are a reliable indicator of the capability of the control to reduce
respirable silica. Therefore, OSHA anticipates that the control
discussed in Carlo et al. (2010) would result in significant reductions
to silica exposures.
    CISC questioned the appropriateness of requiring an integrated
water delivery system when most integrated systems are intended to keep
the blade cool and are not designed for dust suppression (Document ID
2319, p. 109). However product literature submitted to the docket from
five major saw manufacturers (Andreas Stihl, Husqvarna, Hilti, Makita
USA, and Wacker Group) highlights the use of water application
equipment to suppress dust in addition to blade cooling (Document ID
3620, pp. 6, 10, 24, 30; 3998, Attachment 12a, pp. 9, 15-16; 3998,
Attachment 12e, p. 3; 3998, Attachment 12f; 3998, Attachment 12h; 4233,
Attachment 1, p. 6). Beamer et al. (2005) conducted experiments to
observe the differences in the various wet cutting methods available
and found that the greatest improvement in dust reduction occurred with
freely flowing water applied at a rate of 48 gallons per hour (0.8
gallons per minute), resulting in dust reduction of about 93 percent
and confirming the benefits of water flowing over the stationary saw
cutting blade compared with other misting systems (Document ID 1555, p.
509). Therefore, based on the evidence in the record, OSHA has
determined that stationary masonry saws equipped with an integrated
water delivery system are effective and the best available technology
for controlling respirable crystalline silica.
    Several commenters suggested that OSHA include an option for dry
cutting on Table 1 (i.e., using LEV or other non-wet methods to control
dust) because wet methods were not always available and certain
materials are required to be cut dry. Commenters explained that
freezing temperatures, lack of available water sources on new
construction sites, concerns of water damage to surrounding areas
during indoor work and problems with discoloration or water staining
materials were all reasons why an employer may elect to cut without
water (Document ID 0861, p. iv; 1431, pp. 1-6-1-9; 2296, p. 31; 2319,
p. 94; 2320, pp. 6-7; 3587, Tr. 3609-3610; 4220, p. 5).
    OSHA addresses the issue of freezing temperatures and availability
of water in the technological feasibility analysis (Chapter IV of the
FEA) and has determined that these barriers can be overcome in most
instances, for example by wrapping gutter heat tape around drums of
water or adding environmentally-friendly antifreeze additives to water
(e.g., Document ID 3589, Tr. 4214, 4230). Moreover, evidence in the
record indicates that LEV is not as effective as wet methods for
controlling silica dust emissions from stationary saws. In the only
study available to OSHA that directly compared wet dust suppression
with LEV under the same experimental conditions, Carlo et al. (2010)
determined that, even though the use of LEV resulted in substantial
respirable dust capture, the water application system reduced the dust
to a greater extent, reducing respirable dust levels by a factor of 10
more than the LEV systems tested (Document ID 3612, pp.

247-250). Unlike for wet dust control systems, there is little evidence
in the record that LEV systems have proven effective in actual field
use; the database compiled by Flanagan et al. contains no sample
results from using stationary saws with LEV (Document ID 0677,
Attachment 2).
    OSHA finds that the study by Carlo et al. indicates that LEV
systems on stationary saws are not as effective as water-based dust
suppression systems and that respiratory protection will likely be
needed. In the PEA, OSHA acknowledged that there was some evidence that
exposures could be reduced to or below 50 [mu]g/m\3\ with LEV when saws
were used for typical cutting periods (15 to 30 percent of the shift)
but that the effectiveness of LEV systems for stationary saws had not
been widely evaluated. However, no evidence came into the record after
the PEA that would allow OSHA to have greater confidence in the use of
LEV when dry cutting or to consider it to be as effective as wet
cutting in reducing silica dust exposure. Therefore, OSHA has not
included a control alternative for the use of dry cutting with LEV in
Table 1, and is only allowing integrated water systems for compliance
with Table 1.
    OSHA understands that there may be limited situations where the use
of wet systems is not feasible for a given application. For those
situations, the employer may use other means of dust control such as
LEV systems, but the employer must then follow paragraph (d) rather
than paragraph (c) of the standard for construction, i.e., comply with
the 50 [mu]g/m\3\ PEL, perform exposure assessments to determine
compliance with the PEL, and supplement the engineering and work
practice controls with respiratory protection where the PEL is not
being met.
    Stationary masonry saws with integrated water systems are readily
available from several manufacturers including EDCO, Andreas Stihl,
Hilti, Makita USA, Husqvarna, Wacker Group, MK Diamond, and Bosch (for
tile cutting) and are effective and the best control option available
(Document ID 4073, Attachment 4a, Rows 59-63, 183-188, 292-297, 347-
351, 417-419; 4073, Attachment 4b, pp. 10-12, 21; 3998, Attachment 12a;
3998, Attachment 12e; 3998, Attachment 12f; 3998, Attachment 12g; 3998,
Attachment 12h). Therefore, OSHA has determined that an integrated
water delivery system is the appropriate control for inclusion on Table
1.
    In the proposed rule, OSHA required the use of a half-mask
respirator for employees who operated stationary masonry saws for more
than four hours. OSHA made this determination based on the highest
exposure results included in its exposure profile. OSHA has since
determined that when fully and properly implementing all of the
provisions under paragraph (c), employees can operate stationary
masonry saws without the use of respirators. This is supported by the
exposure profile contained in Table 5.7-B in Section 5.7 of Chapter IV
of the FEA, which shows a mean exposure of 41 [mu]g/m\3\, a median of
34 [mu]g/m\3\ and 75 percent of the sample results below 50 [mu]g/m\3\.
Flanagan et al. reported similar exposures with a mean exposure of 48
[mu]g/m\3\ crystalline silica from four exposure samples taken while
workers operated saws indoors or in enclosed areas (Document ID 0677,
Attachment 2). While water use was not described in any detail, these
data show that exposures can be consistently maintained at a level
where respiratory protection is not needed. Therefore, the final rule
does not require the use of respiratory protection when employers are
using wet stationary saws in accordance with Table 1, even when
stationary masonry saws are used indoors or in otherwise enclosed areas
(situations which are the most likely to generate high exposures).
    Handheld power saws (any blade diameter). In the proposed rule,
this entry was listed as ``Using Handheld Masonry Saws.'' OSHA has
changed the title of this entry in the final rule to clarify that the
requirements in Table 1 apply to any use of handheld power saws, not
just those involving masonry materials. However, the tools included
under this entry have not changed and include cut-off, chop, quickie,
and handheld masonry saws.
    Handheld power saws are used in the construction industry for
cutting a variety of materials (see Section 5.6 of Chapter IV of the
FEA). They usually consist of a semi-enclosed circular blade, directly
adjacent to or in front of two handle grips which are perpendicular to
each other. The blade enclosure covers the half (or more) of the blade
directly facing the worker. A worker typically will use the blade to
cut a work piece (e.g., a brick) placed on the ground by starting the
device and slowly lowering the entire handheld saw with both hands to
the work piece until the rotating blade makes contact and begins to
cut, at which point the worker applies pressure to the work piece and
cuts appropriately (Document ID 4073, Attachment 4a, Row 47). A nozzle
for spraying water is usually located near the blade, and a water
source is usually connected to the saw from a water source via a hose
(Document ID 3998, Attachment 12e; 3998, Attachment 12f; 3998,
Attachment 12h, pp. 10-11).
    When using handheld power saws with any blade diameter (except saws
used to cut fiber-cement board), paragraph (c)(1)(ii) of the standard
for construction requires that saws be equipped with an integrated
water delivery system that continuously feeds water to the blade and
that it be operated and maintained in accordance with manufacturer's
instructions to minimize dust emissions. Like stationary saws, designs
vary between manufacturers and, as with other operating parameters,
recommendations for optimizing wet methods are likely to vary somewhat
with the saw size and design. In light of these variables, OSHA is not
specifying a minimum flow rate. In addition, OSHA is recognizing that
the employer's best available information for reducing dust with a
specific control comes from the manufacturer's operating instructions,
which is why OSHA is requiring the saw be operated and maintained
according to the manufacturer's instructions to minimize dust. Water-
fed handheld saws are commercially available from a variety of sources
(Document ID 0615; 0737; 3998, Attachment 12e; 3998, Attachment 12a;
3998, Attachment 12f; 3998, Attachment 12g; 3998, Attachment 12h).
    The data in the record and the studies reviewed by OSHA demonstrate
that water spray suppression systems reduce respirable crystalline
silica exposures substantially where the system was well designed and
properly implemented and maintained (Document ID 0868; 1181; 3497;
3610; 3777; 4073, Attachment 8a). Use of an integrated water delivery
system on the cut-off, chop, quickie or masonry saws has been shown to
reduce respirable dust exposures by 78-96 percent (Document ID 0868, p.
v; 1181, p. 443; 3610, p. 157; 3777, p. 67). Data compiled by the CSDA
from member jobsites as well as NIOSH documents showed that all outdoor
hand sawing using a saw equipped with a water supply produced exposure
levels below a TWA of 50 [mu]g/m\3\ (Document ID 3497, p. 5).
    In a laboratory study, Thorpe et al. (1999) evaluated the
effectiveness of two types of water supplies commonly used with
handheld saws: (1) A pressurized portable water supply and (2) a
constant water supply (Document ID 1181, pp. 443, 445-447). During this
evaluation, 15-minute PBZ samples were collected during uncontrolled
and controlled (i.e., water-fed) cutting of concrete slabs containing
20 percent to 40 percent

silica (i.e., worst-case conditions) (Document ID 1181, p. 447). The
study protocol involved short sampling durations because handheld saws
are typically used intermittently to make short cuts. The uncontrolled
mean silica concentration during multiple 15-minute trials of intensive
cutting ranged from 1,700 [mu]g/m\3\ to 4,800 [mu]g/m\3\ (reported as
1.7 to 4.8 mg/m\3\) (Document ID 1181, p. 448). Reductions in exposure
to respirable silica dust when cutting concrete slabs using wet methods
compared with no controls were 75 percent for diamond blades and 94
percent for resin blades when using water supplied by mains, and 75
percent for diamond blades and 77 percent for resin blades when using
water supplied by a portable tank. Both sources of water were effective
at reducing respirable dust, however, the portable tank needed to be
periodically re-pressurized to maintain the necessary flow rate, while
the water supplied from the mains provided a more constant flow rate.
Both types of systems used to supply water to an integrated water
delivery system would be acceptable under the table.
    NIOSH also evaluated the performance of a commercially available
water backpack and spray attachment, pre-set by the attachment
manufacturer to provide 1.4 liters per minute water consumption (0.36
gallons per minute) for handheld saws during concrete block cutting
(Document ID 0868, pp. 8, 11). The handheld electric abrasive cutter
was used outdoors to make cuts through concrete blocks laid lengthwise
on a plank 17 inches above the ground. During the 5- to 10-minute
trials with water-fed saws, the water spray attachment reduced quartz
exposures by an average of 90 percent from uncontrolled levels
(Document ID 0868, p. 10). Middaugh et al. (2012) conducted a workplace
field study to evaluate the effectiveness of dust controls on cut-off
saws (Document ID 3610, p. 158). Air sampling was conducted for 10 days
at 5 job sites on 4 experienced operators using gas-powered cutoff saws
with 14 inch (35.6mm) diameter blades to cut concrete curbs (Document
ID 3610, p. 159). Air sampling was conducted both with and without wet
methods; sampling ranged from 4 to 16 minutes and corresponded to the
entire duration of the task (Document ID 3610, pp. 159-161). With wet
suppression, the concentration of respirable silica levels was reduced
78 percent to 210 [mu]g/m\3\ (Document ID 3610, p. 162).
    Based on the information in the record, OSHA concludes that most of
the time, handheld power saw operators use the saw for two hours or
less over the course of a workshift, typically using handheld saws for
brief, intermittent periods repeated numerous times over the course of
a shift (Document ID 1431, p. 3-63). The Mason Contractors Association
of America stated that ``90 minutes is actually a really long time to
be cutting something. The vast majority of [cutting tasks] are under 15
minutes [total] in any given day'' (Document ID 3585, Tr. 2911). The
Bay Area Roofers Waterproofers Training Center agreed, clarifying that
when cutting is performed as part of its work it is usually half an
hour to 45 minutes a day (Document ID 3581, Tr. 1598). Information
contained in research supports this as well. Thorpe et al. (1999) used
15-minute sampling durations in the study protocol because handheld
saws are typically used intermittently to make short cuts (Document ID
1181, pp. 447-448). Middaugh et al. (2012) explained that concrete
cutting in roadway construction is frequently performed with a handheld
saw, noting that ``although some applications may require cutting for
an entire 8-hour workday, typical cutting is performed for less than
two hours per day'' (Document ID 3610, p. 162). Sample times from the
Flanagan et al. database support this; the median time for using
handheld portable saws was 101 minutes and the range of cutting times
was from 9 to 447 minutes, indicating that saws are typically used for
only a portion of the shift, although some workers cut for longer
durations (Document ID 0677, Attachment 2).
    Estimated TWA exposures (i.e., averaged over eight hours) using
task measurements from field studies may exceed 50 [mu]g/m\3\ when
workers cut with water for two or more hours per day (Document ID 3610;
4073, Attachment 8a, p. 1; 0868). Shepherd and Woskie (2013) estimated
that if typical cutting conditions (intensive cutting) were performed
outdoors with wet methods for two hours and no other exposure occurred
for the remainder of the day, 83 percent (88 out of 106) of the saw
operators' 8-hour TWA exposures would be 50 [mu]g/m\3\ or less
(Document ID 4073, Attachment 8a, p. 1). In further analysis, the
authors considered what would happen if operators used the water-fed
saws outdoors at this same level of intensity for a full 6 hours of the
shift, in which case 61 percent of operators would have 8-hr TWA
exposures of 50 [mu]g/m\3\ or less (Document ID 4073, Attachment 8a, p.
1).
    In the proposal, OSHA based its requirement to use respiratory
protection for operating saws more than four hours per shift on the few
higher exposure values in its exposure profile, which indicated that
exposures would exceed 50 [mu]g/m\3\ occasionally when wet cutting with
portable saws. However, OSHA concludes that the study by Shepherd and
Woskie (Document ID 4073, Attachment 8a) as well as other material
contained in the record and discussed above provide a better basis on
which to determine the need for respiratory protection. Based on these
studies, OSHA determined that outdoor wet cutting for more than four
hours could result in more frequent exposures over 50 [mu]g/m\3\ than
are experienced with shorter task durations. Therefore, paragraph
(c)(1)(ii) of the standard for construction requires use of respiratory
protection having an APF of at least 10 for employees using a handheld
power saw of any blade diameter equipped with an integrated water
delivery system for more than four hours per shift. When cutting for
four hours or less outdoors, no respiratory protection is required.
    The vast majority of samples reviewed by OSHA involve the use of
handheld saws outdoors. However, employees may occasionally use
handheld saws indoors. When an employee uses a water-based system
indoors or within enclosed areas, elevated exposures can still occur
(Document ID 0675; 0177; 0846; 3497; 3777). Data submitted by CSDA
shows that almost all indoor hand sawing using wet methods produced
exposure levels above 50 [mu]g/m\3\ (Document ID 3497, pp. 1-4, 6, 8).
Additionally, a field study of wet sawing found that an enclosed
location (in a large garage building open in front and closed on 3
sides) resulted in significantly higher exposures than when the work
was done outdoors (Document ID 3777, p. 1); a separate study found
levels as high as 240 and 260 [mu]g/m\3\ during indoor wet sawing
(Document ID 0675, p. 1098). OSHA's exposure profile contained in
Section 5.6 of Chapter IV of the FEA shows that using wet methods
indoors results in higher exposures when compared to outdoor cutting
with only 50 percent of the exposures in indoor environments being 50
[mu]g/m\3\ or less, compared to 80 percent of the outdoor wet sawing
samples. Although wet methods substantially reduce operator exposures
compared to uncontrolled dry cutting indoors, elevated exposures still
occur routinely. To reduce these exposures, OSHA is requiring that work
done indoors or in enclosed areas have

additional general ventilation such as exhaust trunks, fans, air ducts
or other means of forced air ventilation to prevent the accumulation of
dust in the work area. Accordingly, for indoor work, paragraph
(c)(1)(ii) requires the use respiratory protection with an APF of 10
regardless of task duration.
    Representatives from the roofing industry expressed concern
regarding the use of wet methods in their industry, citing primarily
the potential increase in slips and falls from introducing water to
elevated worksites (Document ID 2320, p. 116; 2192, p. 4; 3526, p. 7).
The Tile Roofing Institute stated that in California and Arizona,
rooftop operations with roofing tiles or pavers are given an exemption
from the requirement to use a dust reduction system because there is no
way to address both the silica and fall protection hazard (Document ID
3587, Tr. 3595). Conversely, testimony from the public hearings
indicates that wet dust control systems can be used to reduce exposures
to silica during cutting of roofing tiles and pavers. Dan Smith,
director of training for the Bay Area Roofers and Waterproofers
Training Center, testified that the roofing industry in California is
starting to voluntarily cut roofing tiles and pavers wet (Document ID
3581, Tr. 1600-1601; 1638) and that use of controls may actually
increase visibility, thereby reducing a potential fall hazard (Document
ID 3581, Tr. 1603-1604). He also explained that dry cutting of roofing
tiles is prohibited in the U.K., and that the contractors association
(the National Federation of Roofing Contractors), ``. . . provides
guidance and training. They use wet saws on scaffolding at the roof
level . . . they use a [water] mister on the tile saw. They use a
system like the hytile . . . which is a tile breaking tool'' (Document
ID 3581, Tr. 1601).
    OSHA understands the concerns expressed by representatives from the
roofing industry regarding the use of wet methods and increased risk
for falls; however, OSHA concludes that alternate project planning can
enable employers to use wet methods by implementing some of the
measures described above.
    In the proposed rule, OSHA included an option under Table 1 for the
use of LEV when using portable masonry saws. While including LEV as an
alternative to wet methods in the table was supported by both labor and
industry groups (Document ID 2296, p. 32; 4223, p. 140; 4233,
Attachment 1, p. 1), OSHA has removed this option from Table 1 based on
information contained in the record indicating that LEV cannot
consistently maintain exposure at or below a TWA exposure level of 50
[mu]g/m\3\ (see Section 5.6 of Chapter IV of the FEA). OSHA is not
prohibiting use of LEV for dry cutting, as LEV may be effective in
reducing exposure to or below 50 [mu]g/m\3\ in situations where, for
example, saw use is intermittent. Employers who choose to do so may
still use LEV in lieu of an integrated water system; however, those
employers would be required to comply with the PEL and exposure
assessment requirements under paragraph (d) of the standard for
construction.
    Handheld power saws for cutting fiber-cement board (with blade
diameter of 8 inches or less). These specialized saw configurations
consist of blades (with four to eight teeth) specifically designed for
cutting fiber-cement board (see Section 5.6 of Chapter IV of the FEA)
(Document ID 2322, p. 9; 2322, Attachment B, p. 8). The blades are
fitted to a circular saw (or occasionally to other saws) with dust
reduction systems (Document ID 2322, p. 9; 2322, Attachment B, p. 36).
These saws have been specifically designed and tested by a member of
the fiber-cement siding industry and by NIOSH for controlling the
silica exposure of installers who perform cutting in that industry, and
the saw is intended specifically for use on fiber-cement board
(Document ID 2322, pp. 5, 9; 2322 Attachment B, pp. 33, 36).
    When using handheld power saws with a blade diameter of 8 inches or
less for cutting fiber-cement board outdoors, paragraph (c)(1)(iii) of
the standard for construction requires saws to be equipped with a
commercially available dust collection system that provides the air
flow recommended by the manufacturer and a filter with a 99 percent or
greater efficiency, operated in accordance with the manufacturer's
instructions to minimize dust emissions. OSHA is not providing an entry
for use of these saws indoors on Table 1 because fiber-cement board,
used as siding and fascia applied to the exterior of buildings, is
usually cut outdoors and the record lacks information on exposures to
silica that would result from cutting fiber-cement board indoors.
Therefore, employers who choose to operate saws to cut fiber-cement
board indoors must conduct exposure assessments and comply with the PEL
in accordance with paragraph (d) of the standard for construction.
    This entry was added to Table 1 of the final standard for
construction in response to comments NIOSH and the fiber-cement board
industry submitted to the rulemaking record. These submissions provided
substantial data on control technology (a specially configured saw) for
controlling silica exposure when saw operators cut fiber-cement board
(Document ID 2177, Attachment B, pp. 17-19; 2322, Attachment B-E and
H).
    The James Hardie Building company submitted 75 samples for workers
using specially configured circular saws (with specialty blades of less
than 8 inches) for cutting fiber-cement board with LEV (Document ID
2322, pp. 19-20). These saws were all fitted with cutting blades
designed for the fiber-cement board product and some form of dust
collector (but not always designed with vacuum suction). Workers using
these saws had a mean 8-hour TWA exposure of 11 [mu]g/m\3\ (median 7
[mu]g/m\3\), although elevated exposures (maximum exposure of 76 [mu]g/
m\3\) occurred with some saw/control configurations that proved less
reliable (for example, saws attached to a dust receptacle, without the
benefit of a vacuum dust collection device) (Document ID 2322, pp. 19-
20). Although the cutters sawed fiber-cement board products containing
15 to 50 percent silica, the respirable dust collected in the samples
was 0 to 12 percent silica and percentages in the lower half of that
range were most typical (Document ID 2322, Attachment D, pp. 5-10;
2322, Attachment E, pp. 5-9; 2322, Attachment F, pp. 5-10). Most of the
sawyers for whom exposures were elevated cut siding for approximately
half the shift (four to five hours), a duration representative of
typical cutting activities during a normal day of fiber-cement siding
installation (Document ID 2322, Attachment D, p. 16; 2322, Attachment
E, p. 16; 2322, Attachment F, p. 18). Several NIOSH reports demonstrate
that this and other saw configurations are effective in achieving
exposures of 50 [mu]g/m\3\ or below when the saw is used with a vacuum
dust collector (Document ID 4138; 4139, p. 11; 3998, Attachment 4a;
3998, Attachment 4b; 3998, Attachment 4c).
    Based on the evidence in the record, commercially available dust
collection systems for handheld power saws with a blade diameter of 8
inches or less and a dust collection device providing the air flow
recommended by the manufacturer have been demonstrated to be
particularly effective in controlling silica during outdoor cutting of
fiber-cement board. One type of saw evaluated was a handheld, dust
collecting model equipped with dust collection device rated at 200 cfm
over a 7.25-inch-diameter blade (27.5 cfm per inch); however, the
measured flow rate was reported to be 69 to 106 cfm. Using this
configuration, all 21 exposure

samples taken for siding cutters on construction sites were 41 [mu]g/
m\3\ TWA or less (20 sample results were less than 25 [mu]g/m\3\) while
cutting a variety of fiber-cement board siding products containing up
to 50 percent silica (Document ID 3998, Attachment 4a; 3998, Attachment
4b; 3998, Attachment 4c; 4138; 4139). Accordingly, OSHA is requiring in
paragraph (c)(1)(iii) that dust collectors be used with saws when
cutting fiber-cement board.
    Based on the evidence in the record, OSHA is not requiring the use
of respiratory protection when employees are using handheld power saws
with a blade diameter of 8 inches or less, for cutting fiber-cement
board outdoors in accordance with Table 1 for any task duration. OSHA
has determined that in such circumstances, employee exposures will be
reduced to 50 [mu]g/m\3\ or less when the controls specified for this
task on Table 1 are fully and properly implemented.
    Walk-behind saws. When using walk-behind saws (see Section 5.6 of
Chapter IV of the FEA), paragraph (c)(1)(iv) of the standard for
construction requires that saws be equipped with an integrated water
delivery system that continuously feeds water to the blade and that the
tool be operated and maintained in accordance with manufacturer's
instructions to minimize dust emissions. OSHA is specifying that the
saws be used with an integrated water feed system because the Agency
has identified this as the most effective means of reducing exposures
to respirable crystalline silica. This requirement is essentially the
same as was proposed for the entry ``Using Portable Walk-Behind and
Drivable Masonry Saws.'' As explained below, requirements in the final
rule for drivable saws have been separated from those for walk-behind
saws.
    Saw designs vary among manufacturers, and as with other operating
parameters, recommendations for optimizing wet methods are likely to
vary somewhat with the saw size and design. As with other saws, OSHA is
not specifying a minimum flow rate, but rather anticipates that the
water flow rates specified by the manufacturer will optimize dust
reduction. OSHA recognizes that the employer's best available
information for reducing dust with a specific control comes from the
manufacturer's operating instructions, which is why OSHA is requiring
the saw be operated and maintained according to the manufacturer's
instructions to minimize dust. Water-fed walk-behind saws (manual and
self-propelled) are widely available from many manufacturers and
construction tool distributors, such as Grainger, EDCO, MK Diamond, and
CS Unitec (Document ID 0715; 1676; 1185; 0643; 0615).
    CSDA stated that ``nearly 100% of CSDA contractors use water on
each and every job and this has to do with extending the life of the
expensive diamond tools. The use of water has an additional benefit of
containing silica particles that could become airborne'' (Document ID
3496, p. 3). This was supported by others during the public hearings
(Document ID 3580, Tr. 1438; 3585, Tr. 2885) and in written comments
(Document ID 2316, p. 3). Disagreeing, both SMI and the Mason
Contractors Association of America commented that most water-fed
systems are designed to keep the blade cool, and their ability to
suppress dust has not been sufficiently researched (Document ID 2316,
p. 3; 3585, Tr. 2885). CISC similarly asked whether an additional water
feed is needed for these saws or whether the one currently integrated
for the purpose of cooling the saw will suffice (Document ID 2319, p.
104).
    OSHA finds that considerable evidence in the record shows that
water application reduces dust emissions, and several saw manufacturers
state that using wet cutting will suppress dust (see discussion about
requirements for water delivery systems above). Furthermore, the water
delivery system described in Linch (2002) was for the purpose of
cooling or protecting the blade, but was effective in suppressing
respirable silica levels to below 50 [mu]g/m\3\ (Document ID 0784, p.
216). CSDA submitted exposure data collected during slab sawing with
saws ``equipped with water supply,'' presumably for blade cooling.
Those data show that of 26 measurements of silica concentrations taken
during outdoor work, 21 (80 percent) were less than 25 [mu]g/m\3\, and
only one sample (65 [mu]g/m\3\) exceeded 50 [mu]g/m\3\ (Document ID
3497, pp. 2-4). Therefore, OSHA concludes water provided as coolant can
also control silica exposure.
    CISC questioned the feasibility of using wet methods in situations
where there is no established water main on site (Document ID 2319, p.
112). OSHA finds that water tanks, which were used to provide water to
the walk-behind saws in Linch (2002), are already commonly available on
many construction sites and could provide water for a walk-behind saw
(Document ID 0784, pp. 216-217).
    Data contained in the record show that none of the respirable
silica results associated with wet cutting outdoors using walk-behind
saws exceeds 50 [mu]g/m\3\, with the majority of these results being
less than or equal to the limit of detection (Document ID 0784, pp.
216-217). These results were obtained using the saw's normal water feed
system intended for cooling the blade. Therefore, OSHA has determined
that no respiratory protection is required when working outdoors with a
walk-behind saw for any task duration.
    Since walk-behind saws are used to cut pavement, they are most
commonly used outdoors, though they can also be used indoors (Document
ID 1431, pp. 3-63). Although the data are limited, water-fed walk-
behind saws used indoors or in enclosed areas may result in higher
exposures than those measured outdoors. Studies by both NIOSH and
Flanagan et al. (2001) noted the potential for elevated exposure when
walk-behind saws with continuous water application are used indoors,
with Flanagan et al. reporting four 8-hour TWA sample results between
65 to 350 [mu]g/m\3\ for four to seven hours of work (Document ID 4233,
Attachment 1, p. 10; 0675, pp. 1098-1099). Additionally, the CSDA
report submitted to the record shows the only exposure result from
indoor slab sawing exceeded 50 [mu]g/m\3\ despite the use of equipment
with water supply (Document ID 3497, pp. 2-4). These results indicate
that the source for the elevated exposure is likely due to the build-up
of respirable aerosol within the enclosed space, rather than direct
exposure to slurry spray (Document ID 0675, p. 1099). While OSHA
anticipates that the results for indoor sawing can be reduced by
minimizing the build-up of dust with supplemental ventilation as
required under paragraph (c)(2)(i) of the rule, OSHA is unable to
conclude that exposures can be consistently reduced to 50 [mu]g/m\3\ or
less for this task when performed indoors. Therefore, when used indoors
or in an enclosed area, OSHA is requiring the use of respiratory
protection with an APF of 10 regardless of task duration.
    Drivable saws. Paragraph (c)(1)(v) of the standard for construction
requires that, when using drivable saws to cut silica-containing
materials, the saw must be equipped with an integrated water delivery
system that continuously feeds water to the blade and that the tool be
operated and maintained in accordance with the manufacturer's
instructions to minimize dust emissions. Drivable saws include those
where the operator typically sits in a cab (open or enclosed) away from
the pavement cut point, guiding the saw to make long cuts such as are
common for utility installation along roadways. These saws are
cumbersome to move and are typically only used when

making long cuts. The blade housed by the vehicle can be large (e.g., 8
feet in diameter and 2 inches thick) and is usually equipped with a
water-fed system to cool the blade (Document ID 1431, pp. 3-63--3-64).
The requirement to use integrated water systems on drivable saws is
unchanged substantively from the proposal.
    In its Technological Feasibility analysis (see Section 5.6 of
Chapter IV of the FEA), OSHA analyzes exposures for workers using
drivable saws. The exposure profile includes three samples, two using
wet methods as required by Table 1 and one operating under other
conditions. The two samples taken on workers using wet saws showed TWA
silica exposures of 12 [mu]g/m\3\ (i.e., below the limit of detection
(LOD)) and 33 [mu]g/m\3\ over sampling times of 70 and 125 minutes,
respectively. OSHA considers these exposure results to reflect typical
work patterns in that operators will often operate the saw for one or
two hours before moving the saw to another location. CISC questioned
OSHA's use of short term samples and the assumption of zero exposure
during the unsampled portion of the shift and noted that this could
underestimate the exposures for these workers (Document ID 2319, pp.
51-52). While OSHA acknowledges that this situation may occur at times,
there is no evidence that this is the case for these drivable saws
samples. These samples were collected by OSHA inspectors, who are
instructed to sample for the entire duration of silica exposure.
Accordingly, OSHA concludes that these samples accurately characterize
the sampled workers' exposure.
    In the proposed rule, dust control requirements were specified for
drivable and walk-behind saws together, and the proposed rule would
have required respirator use when operating either saw in indoor or
enclosed environments. In the final standard for construction, the
requirements for these kinds of saws are separated on Table 1 because,
unlike walk-behind saws, drivable saws are rarely, if ever, used in
indoor environments. Because the requirements of Table 1 only apply to
outdoor use of drivable saws, and the data available to OSHA
demonstrate that the wet methods described above can consistently
control exposures in that environment, Table 1 does not require the use
of respiratory protection when these controls are implemented,
regardless of task duration.
    SMI and CISC commented that currently drivable saws use water to
cool the cutting tool, and the effectiveness of cooling water for
respirable crystalline silica dust mitigation has not been
comprehensively researched (Document ID 2316, Attachment 1, p. 3; 2319,
p. 112). SMI stated specifically that ``parameters such as flow rate,
volume, flow delivery characteristics, velocity, and delivery location
have not been evaluated or compared'' (Document ID 2316, p. 3).
However, Atlantic Concrete Cutting agreed that all of its cutting
services were performed with water (Document ID 2367, p. 2), and that
the application of water minimized and most likely eliminated exposure
to respirable crystalline silica. Atlantic Concrete Cutting also stated
that the use of a ``water-fed system that delivers water continuously
at the cut point'' would be an appropriate silica dust control for
drivable saws and that respirators would not be needed to further
protect employees (Document ID 2367, pp. 2-4). In light of this
testimony, OSHA concludes that it is appropriate to permit employers to
fully and properly implement water-based systems on drivable saws in
compliance with Table 1, eliminating their need to conduct exposure
assessments for employees engaged in a task using drivable saws.
Moreover, as reflected in Table 1, OSHA concludes that full and proper
implementation of this control will not require the use of respirators
for this task even if performed for more than four hours in a shift and
so has not included respiratory protection for this task.
    Rig-mounted core saws or drills. Paragraph (c)(1)(vi) of the
standard for construction, an entry for rig-mounted core saws or
drills, was not included in proposed Table 1. Core saws or drills are
used to perform core cutting (also called core drilling, boring, or
concrete coring) to create round holes for pipes, ducts and conduits to
pass through walls, ceilings and floor slabs made of concrete, masonry
or other materials that may contain silica (see Section 5.6 of Chapter
IV of the FEA). Core cutting machines (also called core drills) use a
thin continuous round cutting surface on the round end of a cylindrical
coring tool (``bit'') (Document ID 0679, pp. 18-20). The machine is
typically attached to the surface being drilled (bolted on via a rig
for stability) (Document ID 3998, Attachment 13e, pp. 4, 9). When the
rotating diamond core cutting bit is applied to solid material, the bit
cuts away a thin circle of material. The cut separates the central
``core'' of material, within the circumference of the bit, from its
surroundings, leaving the core generally intact as it is removed from
the hole (Document ID 3501, p. 6). The cylindrical bit can range in
size; for example NIOSH described a coring operation used to produce
holes 2 to 31 inches in diameter in large sections of concrete conduit
(Document ID 0898, p. 6).
    For rig-mounted core drills, there is one specified control that
consists of using a tool equipped with an integrated water delivery
system that supplies water to the cutting surface, operated and
maintained in accordance with manufacturer's instructions to minimize
dust emissions. Based on evidence in the record, OSHA has determined
that baseline conditions for core cutting involve using wet methods and
that most core cutting machines are provided with and intended to be
used with a water feed system (e.g., Document ID 0675, p. 1097; 0679,
pp. 18-21; 0898, p. 6; 3580, Tr. 1415, 1435; 3581, Tr. 1584; 3585, Tr.
2902). Like other saws included in Table 1, these existing systems will
fulfill the requirements of Table 1.
    Comments submitted by SMI expressed confusion as to whether or not
core drilling was included on the table under the entry for drills and
the appropriateness of using LEV as required under the proposed table
during core cutting (Document ID 2316, p. 2). In the proposed rule,
OSHA specifically excluded core cutters from hole drillers using
handheld drills (see PEA, p. IV-403). OSHA did not include this
information because OSHA lacked specific information on exposures to
silica that result from core drilling or from industry's practice of
using water during coring operations. Upon OSHA's review of core
cutter/driller operator exposures and hearing testimony from industry,
OSHA determined that there is the potential for silica exposure when
employing core saws and that these saws are different enough from other
drills and cutting tools to warrant the inclusion of its own separate
entry on Table 1.
    Kellie Vasquez of Holes Incorporated testified that the process of
core drilling is much different than other types of drilling due to the
different drill bits used, resulting in much less silica exposure
(Document ID 3580, Tr. 1484). This is supported by OSHA's review of
record data on core cutting/drilling, which shows that operators
generally experience little or no silica exposure during this low-speed
process, which is already performed using water-fed equipment as a
standard practice (Document ID 0675, pp. 1097-1098; 0898, p. 15).
    Additional exposure data compiled by CSDA from member jobsites
(Document ID 3497) and other studies (Document ID 0675; 0679; 0898)
show that using a

core drill with wet methods results in exposure levels of less than 50
[mu]g/m\3\ (Document ID 3497). During hearing testimony, BCTD commented
that core drills are always used with wet methods (Document ID 3581,
Tr. 1584). This was supported by Kellie Vasquez of Holes Incorporated
who stated that her concrete cutting operations employ water 100
percent of the time (Document ID 3580, Tr. 1483). Accordingly, OSHA
added dust control specifications for core sawing and drilling to Table
1 of the final standard for construction. Because the available
evidence described above demonstrates that using wet dust suppression
systems for core cutting does not result in silica exposures exceeding
50 [mu]g/m\3\, the final standard for construction does not require the
use of respiratory protection.
    Handheld and stand-mounted drills (including impact and rotary
hammer drills). Handheld drills are used to, among other tasks, create
holes for attachments and small openings in concrete and other silica
containing materials (see Section 5.4 of Chapter IV of the FEA). These
drills can: (1) Be electric, pneumatic, or gas-powered; (2) use rotary
hammers or percussion hammers; and (3) be free-standing or stand-
mounted. Handheld drills consist of a handle with a trigger button to
begin drilling, a motor compartment above and perpendicular to the
handle, and a socket to insert drill bits of varying lengths and styles
at the end of the motor compartment. Impact and rotary hammer drills
appear the same, but provide the ability to drill with extra motor-
generated impacts and/or torque. The drills may have a second handle in
front of the main handle for a worker to grasp with the off hand. To
control dust, they may contain attachable dust collection systems where
the end of the drill bit is surrounded by a vacuuming compartment which
connects to the rest of the drill, allowing for dust to be removed
while drilling (Document ID 4073, Attachment 4a, Row 68). Handheld
drills can also be stand-mounted, in which case a drill is turned on
its side and mounted to an adjustable stand, allowing the worker to
drill directly into a work product with precision (Document ID 4073,
Attachment 4a, Row 72).
    Paragraph (c)(1)(vii) of the standard for construction requires
that handheld and stand-mounted drills be equipped with a commercially
available shroud or cowling with dust collection system that provides
at least the minimum air flow recommended by the manufacturer. The dust
collection system must include a filter cleaning mechanism and be
equipped with a filter with 99 percent or greater efficiency. The dust
collection system must be operated in accordance with the
manufacturer's instructions to minimize dust emissions. In addition,
OSHA is requiring that a HEPA-filtered vacuum be used when cleaning
debris from drill holes.
    The proposed Table 1 labeled this category of tools ``Using rotary
hammers or drills (except overhead).'' In response to several comments,
OSHA has revised this description to make clear that drills mounted on
stands are also included and also removed the exclusion for overhead
drilling. For example, SMACNA recommended expanding the entry for
rotary hammers and drills to include overhead drilling, contending that
overhead drilling would be just a safe as other drilling if done as
directed on the table (Document ID 2226, p. 2). The Mechanical
Contractors Association of America commented that overhead drilling
should be included in Table 1 since overhead drilling is a common
operation in several trades (Document ID 2143, p. 2). OSHA received
testimony that overhead drilling along with a drill stand with a vacuum
attachment addresses both ergonomic and silica exposure hazards. After
review of the evidence in the record, OSHA has determined that it is
appropriate to remove the exclusion for overhead drilling in the Table
1 entry for handheld and stand-mounted drills.
    As proposed, Table 1 had separate entries for ``Rotary Hammers or
Drills'' and ``Jackhammers and Other Impact Drillers.'' OSHA received
comments from PTI suggesting that impact drills be covered by the entry
for ``Rotary Hammers or Drills,'' rather than by the ``Jackhammers and
Other Impact Tools'' entry (Document ID 1973, Attachment 1, p. 4).
NIOSH also commented on the potential for confusion, noting that a
rotary hammer or drill is technically an impact driller (Document ID
2177, Attachment B, pp. 32-33). Therefore, the entry for handheld or
stand-mounted drills in final Table 1 covers activities related to the
use of impact and rotary hammer drills. Chipping and breaking
activities, which are associated with more intense silica exposures,
are covered by the entry for jackhammers and handheld power chipping
tools.
    CISC commented that OSHA did not state in the proposed rule that
the dust collection system needs to be ``commercially available''
(Document ID 2320, p. 112). In the final standard for construction,
OSHA has clarified that Table 1 requires that the handheld or stand-
mounted drill be equipped with a commercially available shroud or
cowling with dust collection system. Several drilling equipment
manufacturers sell dust extractors or dust collectors to minimize dust
escaping into the work area. These systems include a vacuum with a
filter cleaning mechanism and a filter with 99 percent or greater
efficiency. Some examples include Bosch, DeWalt, Hilti, and Metabo
(Document ID 3998, Attachment 10; 4073, Attachment 4a, Rows 15-18, 64-
70, 111-119, 189-195, 289-301, 352-357). OSHA has determined that it is
feasible for employers to obtain controls for handheld and stand-
mounted drills that meet the specifications in Table 1.
    Based on evidence in the record, OSHA finds that, for most tools, a
commercial dust control system using an appropriate vacuum will provide
the most reliable dust capture. Average respirable quartz levels varied
among the different cowling/vacuum combinations. In one study, all
commercial cowl/vacuum combinations tested resulted in personal
breathing zone exposures of 28 [mu]g/m\3\ or less during drilling
(Document ID 1142, p. 42). Another study reported median silica
exposures of 60 [mu]g/m\3\ and 45 [mu]g/m\3\, depending on drill bit
size, in a room with limited air exchange (Document ID 1391, pp. 11-12,
15-19). These findings indicate that providing a means of exhaust when
working indoors or in enclosed areas, as required under paragraph
(c)(2)(i) of the standard for construction, in addition to using dust
collection systems, will maintain exposures below 50 [mu]g/m\3\. Based
on these findings, OSHA is not requiring the use of respiratory
protection when using handheld or stand-mounted drills, including
overhead drilling, for any task duration.
    The practice of dry sweeping or brushing debris from a hole, or
using compressed air to clean holes, contributes to the exposure of
employees using drills. Based on the evidence in the record, OSHA is
requiring that holes be cleaned with a HEPA-filtered vacuum. Any method
for cleaning holes can be used, including the use of compressed air, if
a HEPA-filtered vacuum is used to capture the dust. If a HEPA-filtered
vacuum is not used when cleaning holes, then the employer must assess
and limit the exposure of that employee in accordance with paragraph
(d) of the standard for construction.
    While the paragraph on housekeeping (paragraph (f) of the standard
for construction) also applies when employers are following paragraph
(c) of the standard for construction, the employer must ensure that all
of the engineering controls and work practices specified on Table 1 are
implemented.

For example, paragraph (f)(2)(i) of the standard for construction
permits the use of compressed air when used in conjunction with a
ventilation system that effectively captures the dust cloud. However,
to fully and properly implement the controls on Table 1, an employer
using compressed air when cleaning holes during tasks using handheld or
stand-mounted drills or dowel drilling rigs for concrete must use a
HEPA-filtered vacuum to capture the dust, as specified in paragraphs
(c)(1)(vii) and (viii) of the standard for construction, not just a
ventilation system as specified in paragraph (f)(2)(i) of the standard
for construction.
    PCI noted that anchor holes must be blown clean to obtain adequate
adhesion, and recommended that the use of compressed air and dry
sweeping be allowed unless exposures will exceed 50 [mu]g/m\3\
(Document ID 2276, pp. 10-11). This recommendation assumes exposure
assessment, however, the construction standard does not require such
assessment where the task is included in Table 1 and the employer is
following Table 1. Although OSHA is allowing the use of compressed air
if used in conjunction with a HEPA-filtered vacuum to capture the dust,
OSHA has determined that there are a number of feasible alternatives to
using compressed air. At least one tool manufacturer offers an anchor
system with ``no hole cleaning requirement whatsoever,'' due to the use
of a drill with a ventilated drill bit (Document ID 4073, Attachment
4b, Slide 12). Another manufacturer offers a ``hole cleaning kit'' for
large hammer hole drilling, which consists of a doughnut-shaped dust
collection head that attaches directly to a vacuum cleaner hose. The
head is placed against the surface to be drilled and captures dust
generated as the hole is drilled (Document ID 4073, Attachment 4b,
Slide 17). This hole cleaning kit also includes two sizes of hole
cleaning tubes. Such a control could be used with existing as well as
new drills (e.g., Document ID 3998, Attachment 10, p. 42).
    Data suggest that decreasing employees' reliance on blowing or dry
sweeping drilling debris can reduce exposures by approximately 50
percent (e.g., Document ID 1391, pp. 32-33). This 50 percent reduction
would bring exposure levels to 50 [mu]g/m\3\ or below for all the drill
operators who are currently exposed to silica at levels between 50
[mu]g/m\3\ and 100 [mu]g/m\3\. Thus, OSHA has determined that a HEPA-
filtered vacuum must be used when cleaning holes in order to reduce
silica exposure.
    Dowel drilling rigs for concrete. Paragraph (c)(1)(viii) of the
standard for construction covers dowel drills (i.e., gang drills),
which are drills with one or more drill heads used to drill holes in
concrete for the placement of steel supports (see Section 5.9 of
Chapter IV of the FEA). When operating dowel drills, Table 1 requires
that the rig be equipped with a shroud around the drill bit and a dust
collection system that has a filter with 99 percent or greater
efficiency. In addition, Table 1 requires that dust collection
equipment be equipped with a filter cleaning mechanism.
    NIOSH found that employees using compressed air to clean the filter
after dowel drilling resulted in some of the highest measured exposure
to respirable dust during the task, and could cause damage to the
filter (Document ID 4154, p. 26). NIOSH also pointed out that the
reverse pulse feature on the dust collector should preclude the need to
remove filters for cleaning (Document ID 4154, p. 26). OSHA agrees and
has included the specification for a filter cleaning mechanism for
dowel drills in Table 1. Finally, Table 1 requires that a HEPA-filtered
vacuum is used when cleaning holes. OSHA recognizes that it may be
necessary at times for employers to use compressed air to clean holes,
and thus, as with handheld and stand-mounted drills, Table 1 does not
preclude its use when cleaning the debris from holes caused by dowel
drilling, so long as a HEPA-filtered vacuum is employed at the same
time to effectively capture the dust.
    In the proposed rule, OSHA included dowel drills within the entry
titled ``Operating Vehicle-Mounted Drilling Rigs for Concrete.''
However, OSHA has determined that the exposures that result from dowel
drilling rigs equipped with LEV systems are substantially higher than
is the case for vehicle-mounted concrete drilling rigs. Therefore,
respirator requirements are different for the two kinds of equipment
(see Sections 5.4 and 5.9 of Chapter IV of the FEA).
    Exposure information on concrete dowel drilling in the record is
limited but shows that, even with LEV, exposures are likely to exceed
50 [mu]g/m\3\. Exposure studies by NIOSH on concrete dowel drills,
manufactured by both EZ Drill and Minnich Manufacturing, that were
equipped with close capture hoods and a dust collection system showed
that workers were often still exposed to respirable silica dust levels
well above 50 [mu]g/m\3\, with 8-hour TWA exposures to respirable
quartz ranging from 24 to 420 [mu]g/m\3\ with a geometric mean of 130
[mu]g/m\3\ (Document ID 4154, p. 25). NIOSH found that using an air
lance and compressed air to clean holes and to clean the filter and
hoses of the dust collector contributed to these high exposures, and
NIOSH recommended the use of a pneumatic vacuum to clean holes and
components of the dust collector (Document ID 4154, p. 26). The record
contains no information on exposures that result when vacuums are used
to clean holes. As stated previously, exposures that result from dowel
drilling rigs equipped with LEV systems are substantially higher than
is the case for vehicle-mounted concrete drilling rigs. Based on this
information, OSHA has modified the respirator requirement for dowel
drilling, and is requiring the use of respiratory protection with a
minimum APF of 10 regardless of task duration.
    Comments on OSHA's proposed requirements for dowel drilling were
limited. Holes Incorporated, Atlantic Concrete Cutting and CISC all
stated that outdoor concrete dowel drilling should be included on Table
1 (Document ID 2338, p. 3; 2320, p. 14; 2367, p. 4). Atlantic Concrete
Cutting further suggested that the appropriate control for dowel
drilling is to limit this task to outdoors only and ``provide
sufficient ventilation'' (Document ID 2367, p. 4). As suggested, OSHA
has included a separate entry for concrete dowel drilling on Table 1,
but with more detailed control requirements than suggested by Atlantic
Concrete Cutting based on information contained in the record. OSHA
agrees with Atlantic Concrete Cutting that the entry on Table 1 should
be limited to outdoor operations since there is no information in the
record as to the appropriate level of respiratory protection needed
when operating dowel drills in enclosed areas, and has accordingly
revised Table 1 of the final rule to so indicate.
    PCI commented that anchor holes must be blown clean using
compressed air to obtain adequate adhesion (Document ID 2276, p. 10).
In its feasibility analysis, OSHA identified this task as a significant
source of exposure to respirable crystalline silica. Therefore, for the
reasons previously stated, Table 1 also includes a requirement to use a
HEPA-filtered vacuum when cleaning holes, with or without the use of
compressed air, in connection with this task.
    Vehicle-mounted drilling rigs for rock and concrete. Paragraph
(c)(1)(ix) of the standard for construction requires that vehicle-
mounted rock and concrete drilling rigs be equipped with a dust
collection system with a close capture hood or shroud around the drill
bit with a low-flow water spray to wet the dust discharged from the
dust collector, or be operated from within an enclosed cab in

conjunction with water applied at the drill bit for dust suppression
(see Section 5.9 of Chapter IV of the FEA). The specifications of
paragraph (c)(2)(iii) of the standard for construction apply to the
cabs.
    The proposed rule had separate entries for vehicle-mounted drilling
rigs for rock and vehicle-mounted drilling rigs for concrete, both of
which specified a combination of LEV and water use. OSHA has determined
that, since the rigs and the approach to dust control are similar for
both, they can be combined in Table 1 of the final standard for
construction. OSHA has also determined that it is appropriate to allow
employers the option of having the drill operator work within an
enclosed cab meeting the requirements of paragraph (c)(2)(iii) of the
standard for construction and to apply water at the drill bit to ensure
that the operator and other employees assisting are protected when
working near the drill bit.
    Workers using vehicle-mounted drilling rigs position and operate
the drill rigs from control panels mounted on the rigs. These workers
may also perform intermittent tasks near the drilling point such as
fine-tuning the bit position, moving debris away from the drill hole,
and working directly or indirectly with compressed air to blow debris
from deep within the holes. Workers using drilling rigs can be exposed
to dust generated by the action of the drill bit and from dust raised
by air movement or a compressed air nozzle. Although rig-based drilling
is often a one-person job, some of the associated activities, such as
fine-tuning the drill position and clearing debris from in or around
the holes, can be performed by a second worker (Document ID 0908, p. 1;
1563, p. 3).
    In the proposed rule, OSHA specified requirements for the dust
collections systems regarding smooth ducts, transport velocities,
clean-out points, pressure gauges, and activation of the LEV. These
requirements came from a NIOSH evaluation of control technology for
dowel-pin drilling (Document ID 1628). The final rule does not require
these specific control parameters for vehicle-mounted drilling rigs for
rock and concrete. OSHA has determined that dust controls for dowel
drilling rigs are substantially different than vehicle-mounted rock and
concrete drilling rigs; they are addressed separately in the previous
section. Dust collection systems that use a hood or shroud around the
drill bit have been proven effective in reducing exposures to
respirable crystalline silica. NIOSH found that, when used properly,
modern shroud designs now help achieve dust control objectives more
consistently for rock drilling rigs than in the past (Document ID 0967,
pp. 5-9). Based on information contained in the record, OSHA finds that
dust collectors and shrouds are commercially available (Document ID
0669; 0813).
    Although the LEV system will control dust emissions at the drill
bit, there are still dust emissions at the dust collector discharge
area, which can contribute to either the operator's or other employees'
exposures. Organiscak and Page (1995) found that enclosing the dust
collector discharge area with a shroud can reduce respirable dust
levels by 80 percent (Document ID 3613, p. 11). However, evidence in
the record shows that the combination of LEV at the drill bit and water
application will be more effective in that water can be used to control
dust emission points where drilled material is discharged. Organiscak
and Page (1995) illustrated the effectiveness of combined wet methods
and dust collectors in their U.S. Bureau of Mines study, which compared
rock drilling using LEV with and without the addition of water for dust
suppression. The addition of wet methods to the LEV system showed a 92
percent reduction in respirable dust and eliminated nearly all of the
visible dust. Quartz results decreased from 143 [mu]g/m\3\ when the
water was off (LEV alone) to 9 [mu]g/m\3\ when water was added. OSHA
obtained sample results of 54 [mu]g/m\3\ and 35 [mu]g/m\3\ during an
inspection for two workers drilling in granite that contained 30-40
percent crystalline silica (Document ID 0034, pp. 8, 23-26, 35-38).
Both drillers were reportedly using water and LEV, although specific
details about the configuration of the controls were not discussed
(Document ID 0034, pp. 23, 89-93). A third sample that was below the
limit of detection for crystalline silica was collected on the same
site for a laborer who helped with positioning the drills (Document ID
0034, pp. 39-42).
    OSHA received many comments related to the proposed requirements
for rock and concrete drillers. CISC noted that it is more common to
use wet methods when operating vehicle-mounted drilling rigs for rocks
as opposed to using dust collection systems (Document ID 2319, pp. 108-
109). A number of other commenters noted the prevalence of wet methods
use in the industry (e.g., Document ID 1983, pp. 1-2; 2116, Attachment
1, p. 33; 3496, p. 6). For instance, CSDA commented that nearly 100
percent of CSDA contractors use water on every job in order to prolong
the life of the diamond blade (Document ID 3496, p. 6). The National
Ground Water Association (NGWA) noted that it is industry practice when
drilling water wells to use foam as a wet control method:

    Industry practice is to use the engineering control of soap
injection where water is mixed with foam. The foam mixtures of water
and foam products are effective in mitigating the hazard of dust
when properly used as they can carry particles ranging from .03 mm
to the size of a quarter. There are multiple manufacturers of the
foam products and these products have been approved for use when
drilling sanitary water wells. The foam agents are NSF approved and
have also been approved for use in many states (Document ID 1983,
pp. 1-2).

    NGWA also explained that all rotary drilling machines have been
equipped with some type of water injection system since the early 1970s
(Document ID 1983, p. 2).
    Historically, construction and mining investigators have reported
dust control efficiencies of 96 to 98 percent through the routine use
of wet dust suppression methods, depending on the methods used;
however, the water flow necessary for dust control can create problems
under certain working conditions (e.g., moisture shortening the life of
certain drill bits (such as tricone roller bits), high-pressure water
causing spalling of the drill hole wall) (Document ID 0967, p. 6).
Advances in recent decades have produced equipment that permits workers
to use wet methods in a wider range of circumstances. New ``water
separator sub'' designs extend bit life beyond the previous norm and
reduce spalling in a variety of rock types (Document ID 0967, p. 6).
Several commenters stated that wet methods are used frequently and are
effective in controlling dust (Document ID 1983, pp. 1-2; 3580, Tr.
1435; 3496, p. 6).
    OSHA's exposure profile contains five sample results for workers
using wet methods with no other controls while drilling. These five
samples have a mean of 24 [mu]g/m\3\ and a median of 17 [mu]g/m\3\,
with a high exposure of 57 [mu]g/m\3\ and two results below the LOD
(Document ID 0034; 0226). A review of studies by NIOSH (2008) evaluated
the use of wet methods in different types of drilling, including roof
bolting (rock bolting) and surface rock drilling (Document ID 0967).
NIOSH found that for roof bolting, silica dust was best controlled at
its source through dust collection or wet drilling, similar to the
standard practice in metal mines of using pneumatic percussion drills
with water in addition to compressed air to flush the drill cuttings
from the hole. This drilling method was found to be the best method of
dust control, with

dust reductions ranging from 86 percent to 97 percent (Document ID
0967, pp. 2, 4). The high dust reductions from wet drilling were
confirmed in later studies that evaluated the use of water mists and
foams injected through the drill steel and found that those controls
reduced dust concentrations by 91 percent and 96 percent, respectively
(Document ID 0967, p. 2). NIOSH also found that for surface drilling,
wet drilling techniques provided the best dust control. Wet drilling
provided dust control efficiencies of up to 97 percent at a water flow
rate of 4.5 L/min (1.2 gallons per minute) (Document ID 0967, p. 6).
OSHA thus finds that water directed at the material discharge point is
an effective dust suppressant in vehicle-mounted rock and concrete
drilling and specifies its use on Table 1 for this task.
    OSHA also finds that the use of an enclosed cab can effectively
reduce exposures for vehicle-mounted drill operators. Enclosed cabs,
however, only benefit the operator when the operator remains in the
cab, and they do not control employee exposure during positioning or
hole-tending activities. Therefore additional controls are necessary to
protect employees from exposure to silica dust when performing
activities outside of the cab. As described above, OSHA has determined
that the use of water for dust suppression on the drill bit will
effectively reduce exposures in situations where employees must also
perform activities outside the cab.
    Based on the information discussed above, Table 1 of this standard
provides the option for employees to operate a vehicle-mounted rock or
concrete drill from within an enclosed cab in conjunction with water
applied at the drill bit for dust suppression; wherever cabs are
specified in Table 1, however, the cabs must meet the requirements of
paragraph (c)(2)(iii) of the standard for construction, as discussed
above. OSHA has determined that the enclosed cab will adequately
protect the operator while the addition of water at the drill bit will
reduce exposures for employees in the area. The alternative control
option included in Table 1, a dust collection system and water sprays
at the discharge point (where the system ultimately dumps extracted
dust), has also been proven to reduce exposures for both the operator
at the drill controls and those employees in the vicinity. When the
specified dust control methods are fully and properly implemented, TWA
exposure levels are expected to remain below 50 [mu]g/m\3\, and
therefore, Table 1 does not require use of respiratory protection
regardless of task duration for either control option. In the proposed
rule, OSHA required the use of respiratory protection when the task
lasted more than four hours. However, this was due to the inclusion of
dowel drilling rigs within the entry for ``Operating Vehicle-Mounted
Drilling Rigs for Concrete.'' As explained above, OSHA has determined
that the exposures that result from dowel drilling rigs equipped with
LEV systems, for which respirators are required regardless of task
duration, are substantially higher than is the case for vehicle-mounted
concrete drilling rigs.
    IUOE commented that Table 1 would be clearer if it specified that
employers who use open cabs during concrete drilling are not exempt
from exposure assessment when employers implement the other controls
listed for vehicle-mounted drilling rigs for concrete (Document ID
2262, Attachment 1, p. 48). OSHA considers the rule to be clear as
written: If an employer chooses to operate vehicle-mounted drilling
rigs for rock and concrete from within an enclosed cab, it must follow
the requirements in paragraph (c)(2)(iii) of the standard for
construction and apply water for dust suppression at the drill bit.
Otherwise, the employer must follow the alternative shrouded dust-
collection-system compliance method in Table 1 or the requirements in
paragraph (d) of the standard for construction, which allow for
alternate exposure control methods provided that employee exposures are
assessed and exposures are kept at or below the PEL. Additionally, IUOE
suggested that OSHA explicitly state on Table 1 that the employer does
not have the option of respirator use as a means to control exposures
during rock crushing or rock and concrete drilling if the employer
chooses not to use enclosed cabs as an engineering control (Document ID
2262, Attachment 1, p. 48). OSHA notes that Table 1 of this final
standard does not require that drilling rig operators work from
enclosed cabs exclusively. Because employers can choose between the two
control methods listed on Table 1, employees that use open cabs during
drilling activities would not be required to conduct exposure
assessments if they are using a dust collection system with a close
capture hood or shroud around the drill bit and are ensuring that the
material at the dust collector discharge point is being wetted. If that
method is followed, OSHA, having found based on the exposure profile
and record evidence that exposures will consistently be at or below the
PEL, has not included a respirator requirement on Table 1; where
respirators are not required to satisfy compliance obligations (as is
the case here if Table 1 is fully and properly implemented), OSHA does
not expect employers to require the use of respirators anyway. However
employers that do not follow either control strategy specified in Table
1 must comply with paragraph (d) of the standard for construction,
which could require respirator use if exposures are measured at or
above the PEL when using feasible engineering and work practice
controls.
    IME stated that the final rule should allow for the use of
equivalent, alternative control methods (Document 2213, Attachment 1,
p. 2). Table 1 is intended to represent the most reliable control
methods available for reducing exposures, based on the evidence
contained in the record. Employers who wish to implement an alternative
control method can do so, but those employers must comply with
paragraph (d) of the standard for construction.
    IUOE, among others, urged OSHA to explore additional options for
exposure controls to protect operators working outside the cab when
drilling. Both IUOE and Fann Contracting asserted that Table 1 does not
address protection of operators who perform construction activities
outside the cab with or without remote controls (Document ID 2262,
Attachment 1, p. 45; 2116, Attachment 1, p. 5). In response, Table 1 of
the final standard now includes a requirement to use water for dust
suppression at the drill bit when the drill is being operated from an
enclosed cab to minimize the exposure to other employees outside the
cab.
    OSHA's proposed Table 1 entry for rock drilling would have required
that employees use respirators when working under the shroud. OSHA
proposed this requirement based on a determination that employees'
exposures would be high given their proximity to the point of dust
generation. IME suggested that respirators should not be required at
all times because there are circumstances where the time spent working
under the shroud is extremely brief or infrequent and potential
exposures will be minimal or negligible (Document ID 2213, p. 2). NUCA
commented that this requirement creates hazards for employees working
under the shroud (Document ID 2171, p. 10). In response to these
comments and after reviewing the record, OSHA has not retained this
respirator requirement in the final standard. The Agency finds that the
record contains substantial evidence that when the dust controls
required by Table 1 are fully and properly implemented, TWA exposures
to silica are unlikely to exceed 50 [mu]g/m\3\

(see Section 5.9 of Chapter IV of the FEA). In reviewing dust controls
historically for drilling operations, NIOSH found that, when used
properly, modern shroud designs now help achieve dust-control
objectives more consistently than in the past (Document ID 0967, pp. 5-
9). Furthermore, the record indicates that work under a shroud is
periodic or intermittent and contains no evidence suggesting that this
work is likely to result in silica exposures exceeding 50 [mu]g/m\3\ as
an 8-hour time-weighted average. Accordingly, Table 1, unlike in the
proposed rule, does not include a respiratory protection requirement
for rock and concrete drillers on open (or enclosed) vehicle-mounted
rigs.
    NSSGA recommended that OSHA clarify the requirement for wearing
respirators while working under the shroud by replacing the term
``shroud'' with ``engineered fugitive dust control method, e.g., a
shroud, water spray, etc.'' (Document ID 2327, Attachment 1, p. 21).
Since the Agency has eliminated the requirement for using respirators
under the shroud, NSSGA's suggestion is moot.
    Jackhammers and handheld powered chipping tools. Hand-operated
breaking and chipping power tools and equipment, commonly known as
jackhammers, pavement breakers, breaker hammers, percussion or chipping
hammers, and needle guns, are used in construction for fracturing
materials, which often include silica (e.g., rock, concrete, asphalt,
or masonry surfaces), by delivering rapid repetitive blows (see Section
5.5 of Chapter IV of the FEA). The hammers typically consist of a large
compartment containing a motor, two attached handles to grip the tool,
and a large socket out of which the drill or hammer-like metal
breaking/chipping implement extends. A worker typically will aim the
metal drill/hammer at a target surface while standing one to five feet
away either directly overhead or at an angle, and press the point of
contact into the surface to break, fracture, or chip away at it
(Document ID 4073, Attachment 4a, Row 199).
    In the proposed standard, this entry was titled ``Using Jackhammers
and Other Impact Drillers.'' OSHA had a separate entry for ``Rotary
Hammers or Drills.'' NIOSH commented on the potential for confusion
with these titles, noting that a rotary hammer or drill is technically
an impact driller (Document ID 2177, Attachment B, pp. 32-33). OSHA has
revised the headings for the relevant Table 1 entries ((c)(1)(vii) and
(x)). The revised heading for paragraph (c)(1)(x) removes the term
``other impact drillers'' and replaces it with ``handheld powered
chipping tools.'' This change was made to clarify that this entry
applies only to handheld tools that use an impact movement to chip or
fracture the material being worked on. The heading for (c)(1)(vii) was
revised from ``Using Rotary Hammers of Drills'' to ``Handheld and
Stand-Mounted Drills (Including Impact and Rotary Hammer Drills)'' in
order to clarify that all handheld drills, including impact drilling,
are covered under that entry.
    When using jackhammers and other handheld powered chipping tools at
construction sites to fracture silica-containing material, paragraph
(c)(1)(x) of the standard for construction requires the employer to
operate the tools using either a water delivery system that supplies a
continuous stream or spray of water at the point of impact, or a tool
equipped with a commercially available shroud and dust collection
system operated and maintained in accordance with manufacturer's
instructions to minimize dust emissions. If the employer is operating a
tool with the shroud and dust collection system, Table 1 requires that
the dust collector (i.e., LEV) must provide at least the air flow
recommended by the tool manufacturer, and have a filter with 99 percent
or greater efficiency and a filter cleaning mechanism. These specified
controls are essentially the same as those that were proposed, but the
final standard makes clear that if a shroud and dust collector are
used, it must be commercially available equipment. Unlike the use of a
shrouded dust collection system, a water delivery system is not
required to be commercially available but can be assembled and
installed by the employer.
    OSHA revised the respirator use requirements from the proposed rule
by distinguishing between indoor and outdoor environments. Table 1 of
the final standard for construction does not require respiratory
protection if tools are used outdoors for four hours or less per shift.
OSHA based this revision on record evidence showing that exposures can
be maintained at or below 50 [mu]g/m\3\ using either water sprays or
LEV, provided work does not exceed the median task duration (231
minutes) reported by Flanagan et al. (Document ID 0677, p. 147; 0677,
Attachment 2) (see Section 5.5 of Chapter IV of the FEA). If tools are
used outdoors for more than four hours per shift, Table 1 requires the
use of respiratory protection having a minimum APF of 10 to ensure that
employees are protected from exposures above 50 [micro]g/m\3\. If the
tools are used indoors or in an enclosed area, Table 1 requires the use
of respiratory protection having a minimum APF of 10 to ensure that
employees are protected from exposures above 50 [micro]g/m\3\,
regardless of the amount of time the tools are operated during the work
shift.
    NUCA testified during the hearing that jackhammering is one of the
construction activities most likely to expose employees to silica
(Document ID 3583, Tr. 2255). OSHA's exposure profile for this task
confirms this (Table IV.5.5-B in Section 5.5 of Chapter IV of the FEA);
73 of 98 TWA sample results (74 percent) were above 50 [micro]g/m\3\
for workers using jackhammers and handheld power chipping tools
operated without controls. For tools operated with water, 12 of 16 TWA
sample results (75 percent) exceeded 50 [micro]g/m\3\, but information
on how the water was applied and whether it was sufficient was lacking.
Various studies have demonstrated that properly used wet methods can
substantially reduce respirable silica levels by 90 percent and higher
(Document ID 0865, p. iv; 0867, p. 3; 0838, p. 1; 0914; 1267, pp. 493-
494; 2177, Attachment D, p. 19). NIOSH studies that examined water
spray devices designed to optimize dust suppression (directed mist or
solid cone nozzle) have found that dust and/or silica exposures are
reduced by 72 to 90 percent at a flow rate of approximately 350
milliliters per minute (ml/min) (Document ID 0865; 0867; 1267, pp. 493-
494). Although not commercially available at this time, the record
shows a number of examples of water suppression systems that have been
developed and tested and are ready for commercial introduction or can
be easily assembled from readily available hardware materials and
instructions from the New Jersey Laborers' Health and Safety Fund
(Document ID 0741; 0838; 0914; 2177, Attachment D, pp. 4-7; 3732,
Attachment 3, p. 10).
    The shroud and LEV control for jackhammers and handheld powered
chipping tools was found to be less effective than water suppression
but still reduced exposures up to 69 percent (Document ID 1267, pp.
493-494; 0865, p. iv; 0651, p. 1; 0667, pp. 1-3; 0862, pp.10-11, 14).
Also, the respirable silica levels generated by these tools are
dependent on whether they are being operated outdoors, indoors, or in
an enclosed area. Several powered impact tool manufacturers currently
offer LEV options (e.g., Document ID 1288 p. 2; 1700, p. 1). Other
companies specialize in manufacturing after-market shrouds or exhaust
ventilation systems for various handheld tools such as jackhammers and
chipping equipment

(Document ID 0566, p. 1; 1264, pp. 4-9; 1266, pp. 9-28; 1671; 1366;
1399; 3806, pp. 272-273, 276).
    OSHA received a number of comments on the jackhammer and handheld
powered chipping tool entries on Table 1. CISC commented that OSHA did
not indicate in the proposed Table 1 that the dust collection system
needed to be commercially available and did not set parameters for the
functioning of the dust collection system (Document ID 2319, p. 107).
Based on comments and testimony in the record, OSHA has clarified the
entry in Table 1 for jackhammers and handheld powered chipping tools to
read ``use tool equipped with commercially available shroud and dust
collection system.'' OSHA has added to Table 1 the following
requirements: Operate and maintain the tool in accordance with the
manufacturer's instructions to minimize dust emissions; provide at
least the air flow recommended by the tool manufacturer; and use a
filter with a 99 percent or greater efficiency and a filter cleaning
mechanism.
    CISC also expressed concern that using wet methods may raise
quality issues, for example by introducing water to the base when
pouring new concrete (Document ID 2319, p. 107). The water delivery
system required by Table 1 must deliver a continuous stream or spray of
water at the point of impact. The water delivery system evaluated by
NIOSH delivered between 250 and 300 ml of water per minute and the
authors observed that water applied at these flow rates did not add a
substantial amount of water to the work surface nor did it result in
substantial accumulation of water (Document ID 0867, pp. 8, 15). Given
that a substantial amount of water is not needed, OSHA finds that
proper implementation of the water delivery system is unlikely to lead
to quality control issues. Furthermore, other than the hypothetical
situation raised by CISC, there is no evidence in the record showing
that using wet methods with jackhammers and powered chipping tools
results in quality issues. Furthermore, Table 1 of the final standard
provides two options for dust control of jackhammers and handheld
powered chipping tools. The employer can use a tool that is equipped
with a commercially available shroud and dust collection system as an
alternative to using water.
    Some commenters discussed that water may introduce slip hazards;
however, comments and hearing testimony described current contractor
practices that countered these concerns (Document ID 2171 p. 4; 3589,
Tr. 4295-4296). OSHA understands the concerns about possible slip
hazards from the use of water; however, NIOSH investigators noted that
the relatively low water flow rates (300 ml/min) used to suppress dust
during jackhammering did not result in a substantial accumulation of
water on work surfaces. OSHA expects that proper implementation of the
water delivery system will include taking measures to contain any
runoff to prevent the accumulation of water on walking and working
surfaces.
    The water delivery systems described in OSHA's feasibility
assessment chapter on jackhammers, chipping hammers, and other powered
handheld impact tools (see Section 5.5 of Chapter IV of the FEA),
include portable water tank systems that can easily be brought to a
construction site by a pickup truck or trailer, even in a remote area
(Document ID 0867, p. 4; 0741 p. 1). These water delivery systems can
be operated by one worker and would not require a second worker to
supply the water at the point of impact (Document ID 0838, p. 2).
    Handheld grinders for mortar removal (i.e., tuckpointing). Handheld
grinders are tools fitted with rotating abrasive grinding blades,
discs, or small drums. Tuckpointers are a subset of grinders who
specialize in removing deteriorating mortar from between bricks and
replacing it with fresh mortar (``tuckpointing'') (see Section 5.11 of
Chapter IV of the FEA). Tuckpointing is most commonly performed for
exterior wall maintenance and so generally occurs outdoors, but can
occur indoors where there is interior masonry. The initial phase of
tuckpointing involves using handheld grinders to grind old mortar from
between bricks on a section of the wall. A grinder typically has two
handles that can form various angles with each other and are connected
to a rotating blade located between them. The worker typically holds
one handle in each hand, forming an angle allowing the worker to press
the rotating blade against the mortar between bricks to abrasively
remove it (Document ID 4073, Attachment 4a, Row 226).
    Paragraph (c)(1)(xi) of the standard for construction requires that
this task be performed using a grinder equipped with a commercially
available shroud and dust collection system and operated in accordance
with manufacturer's instructions. Additionally, the dust collection
system must be capable of providing at least 25 cfm of air flow per
inch of wheel diameter and be equipped with a filter that has a 99
percent or greater efficiency and either a cyclonic pre-separator or a
filter cleaning mechanism. The proposed requirement was similar but
specified the air flow to be at least 80 cfm, rather than 25 cfm per
inch of blade diameter, and also included a number of work practices.
OSHA revised the controls for this task based on comments received in
the record, as described below.
    BCTD commented that ``Tuckpointing,'' as the entry was titled in
proposed Table 1, is an operation that consists of a series of tasks
(chipping or cutting out old mortar, preparing replacement mortar,
cleaning the joints, applying fresh mortar, and applying a sealer),
while the listed control was clearly directed at the task of using a
``hand-operated tuckpoint grinder'' (Document ID 2371, p. 25). To
clarify its intent to address the grinding of old mortar, OSHA has re-
named the entry for paragraph (c)(1)(xi) of the standard for
construction to be ``Handheld grinders for mortar removal (i.e.,
tuckpointing).''
    Recent dust control efforts for tuckpointing have focused on using
a dust collection hood (also called a shroud) that encloses most of the
grinding blade and a vacuum cleaner system that is used to suction
(exhaust) air from these hoods to collect dust and debris. These shroud
and vacuum combinations generally capture substantial amounts of
debris. In hearing testimony, Tom Ward, representing BAC, showed a
video of local exhaust engineering controls for tuckpointing and
described them as ``extremely effective'' (Document ID 3585, Tr. 3069).
However, OSHA's exposure profile for tuckpointing shows that, even with
these controls, silica exposures often exceed 100 [micro]g/m\3\ (25
percent of results exceed 250 [micro]g/m\3\ when workers use LEV for
outdoor tuckpointing). An additional survey added to the rulemaking
record reported results at two tuckpointing sites using vacuum and
shroud systems. Air samples taken during 201 to 385 minutes of mortar
grinding showed 8-hour TWA silica exposures ranging from 74 to 1,100
[micro]g/m\3\ (Document ID 4073, Attachment 9l, p. 4).
    CISC questioned why employers can only use commercially available
shrouds for hand-operated grinders, eliminating the use of specialty
manufactured products (Document ID 2319, p. 110). OSHA is unsure of
what CISC means by ``specialty manufactured products'' and CISC's
written comments and testimony did not provide further detail. However,
it is not OSHA's intent to eliminate the use of products that are
custom made by aftermarket manufacturers (i.e., made by someone other
than the original tool manufacturer) which are intended to fit the make
and model of the grinder and

designed to meet the particular needs and specifications of the
employer purchasing the product. The ``commercially available''
limitation is meant only to eliminate do-it-yourself on-site
improvisations by the employer. OSHA's technological feasibility
analysis provides ample evidence that exposures to silica are
substantially reduced when using commercially available dust controls
(see Chapter IV of the FEA). To meet the requirements of Table 1,
however, any specialty manufactured product has to satisfy all the
requirements for this entry.
    In proposed Table 1, OSHA specified that the dust collection system
used must provide at least at 80 cfm airflow through the shroud. For
the final standard, Table 1 requires that dust collectors have an air
flow of at least 25 cfm per inch of wheel diameter. This change is due
to OSHA's review of the evidence in the rulemaking record.
Computational and laboratory studies by Heitbrink and Bennett (2006)
and Collingwood and Heitbrink (2007) found that an air flow rate of 80
to 85 cfm (based on a 4- or 4.5-inch wheel) is the minimum needed to
efficiently capture dust generated by angle grinders used for
tuckpointing (Document ID 0728, p. 366; 0600, p. 877). ACGIH (2010)
recommends 25 cfm to 60 cfm per inch of blade diameter (Document ID
3997, pp. VS-40-01--VS-40-03). For a typical 4-inch tuckpointing blade,
25 cfm/inch of diameter is equivalent to 100 cfm, higher than the 80 to
85 cfm used by Heitbrink and Bennett (2006) and Collingwood and
Heitbrink (2007). Laboratory tests conducted by Heitbrink and Bennett
indicate that a vacuum and shroud used by tuckpointers during grinding
can reduce respirable dust emissions by a factor of more than 400 under
ideal circumstances, but this reduction factor dropped to 10 when
vacuum air flow was reduced to less than 80 cfm (Document ID 0728, p.
375). Furthermore, computational modeling showed that even a modest
decrease in the air flow rate, from 85 cfm to 70 cfm, cuts the shroud's
ability to capture dust by more than half. As a result, the estimated
worker exposure level would be twice as high as it would have been if
the air flow rate had remained constant at 85 cfm.
    A NIOSH field trial on a vacuum that generated an air flow of 111
cfm for a grinder with a 4-inch blade showed that exposure levels for
respirable dust were cut in half compared to using a 76 cfm flow rate
(Document ID 0863, pp. 24-35). Based on the evidence contained in the
record, OSHA has determined that the ACGIH (2010) recommendations are
more protective given the variety of blade diameters, and is requiring
a minimum 25 cfm of airflow per inch of grinding blade diameter instead
of the 80 cfm minimum airflow (regardless of blade diameter) through
the shroud.
    To adequately capture debris during the grinding phase of
tuckpointing, OSHA is requiring that vacuums be equipped with a
cyclonic pre-separator to collect large debris before the air reaches
the filters or be equipped with a filter cleaning mechanism. Cyclonic
pre-separators minimize the accumulation of debris on filters in the
vacuum, enhancing the ability of the vacuum to maintain the initial air
flow rate. When testing a vacuum cleaner model equipped with a cyclonic
pre-separator, Collingwood and Heitbrink found that the collected
debris caused the average air flow rate to decrease only from 90 cfm to
77 cfm (Document ID 0600, p. 884). Heitbrink and Santalla-El[iacute]as
evaluated two different brands of commercially available vacuum
cleaners (Tiger-Vac and Dustcontrol) incorporating cyclonic pre-
separation. Air flow rates for both of these vacuums were ``largely
unaffected'' by debris accumulation up to 35 pounds. Debris
accumulation also had very little effect on the flow rate measured
before and after the filter was cleaned (Document ID 0731, pp. 377,
380). Similarly, during the Collingwood and Heitbrink field trials, the
Dustcontrol vacuum with cyclonic pre-separator did not lose as much air
flow as the vacuum designed with vacuum cleaner bags (bags are a more
common pre-separation method but are subject to clogging) (Document ID
0600, pp. 883-884). OSHA concludes that cyclonic pre-separation is an
effective technology for helping to maintain air flow and vacuum system
effectiveness for the duration of tuckpointing tasks by preventing the
static pressure increase caused by clogging that would otherwise lead
to a dramatic decrease in air flow and loss of effective dust capture
at the shroud.
    The accumulation of material and debris on the filter (filter
caking) during work causes pressure losses that eventually limit air
flows in even the most powerful vacuums. As debris accumulates, the
filter becomes caked with collected dust and air flow decreases. Unless
the filter is properly cleaned following manufacturer's
recommendations, the air flow declines rapidly. Cooper and Susi used a
Dustcontrol 2900c vacuum with ICS Dust Director shroud and Bosch
tuckpointing grinder to evaluate dust control in a field experiment.
The authors reported that in four hours of continuous grinding up to
130 pounds of dust was collected, and that flow rates in the vacuum
dropped from 90 cfm to 80 cfm in as little as 8 minutes. Thus, regular
stops to conduct the proper reverse air pulse filter cleaning procedure
were crucial to successful dust control (Document ID 4073, Attachment
9M, pp. 4-5, 7-9). Therefore OSHA is requiring the use of a filter-
cleaning mechanism when a cyclonic pre-separator, which removes larger
debris, is not in place. To assist employees in determining when it is
time to run a filter cleaning cycle, vacuums equipped with a gauge
indicating filter pressure or equivalent device (e.g., timer to
periodically pulse the filter) may be useful (Document ID 0731, p.
885).
    PTI and OEHCS submitted comments emphasizing the importance of
effective HEPA filtration in protecting employees from silica dust, and
recommended that Table 1 require that dust collectors used with
grinders be equipped with HEPA filters (Document ID 1953, pp. 3-4;
1973, p. 2-3). However, HEPA filters may rapidly clog during mortar
grinding, leading to static pressure drop and loss of air flow needed
to capture dust (see discussion about requirements for dust collection
systems above). Instead, OSHA is requiring filters having at least 99
percent dust capture efficiency.
    In proposed Table 1, OSHA included a specification that the grinder
be operated flush against the work surface and that work be performed
against the natural rotation of the blade (i.e., mortar debris directed
into the exhaust). A number of commenters discussed the difficulties of
complying with this specification (Document ID 2183; 2319). Western
Construction Group commented that it is not possible to always keep the
grinder flush with the surface because the blade will be spinning at
its full speed when cutting into the wall and when the blade is
extracted from the surface, and explained that it would be difficult to
keep the blade flush when removing vertical mortar joints (Document ID
2183, p. 2). OSHA acknowledges there are circumstances that do not
always permit the tool to be operated in this manner, and has therefore
removed this provision from Table 1. However, it is OSHA's position
that full and proper implementation of Table 1 controls includes
keeping the blade flush with the surface whenever possible, in order to
optimize the effectiveness of local exhaust capture (e.g., Document ID
0728, p. 376; 0600, p. 876).
    Western Construction Group also commented that it is not always
possible to operate the grinder against the natural rotation of the
blade,

because a wall needs to be ``prepped'' in order to be in sufficient
condition for mortar to be placed back into the wall (Document ID 2183,
pp. 2-3). Western Construction Group explained that during final
preparation, the blade needs to make short passes back and forth to
clean the joint and prepare it, and that if workers only operated in
one direction, they would place a significant burden on their shoulders
and backs by having to make more passes on the wall to clean the joint
(Document ID 2183, p. 3). Similarly, CISC commented that workers must
move the grinder back and forth in short, deliberate motions when
detailing the joint in order to provide the necessary quality finish
(Document ID 2319, p. 106). OSHA recognizes that the requirement to
operate against the direction of blade rotation may have an impact on
job quality and may increase ergonomic stress. While OSHA has removed
this specification from Table 1, it is OSHA's expectation that full and
proper implementation of Table 1 controls includes operating against
the direction of blade rotation, in accordance with the manufacturer's
instructions, whenever practical.
    CISC commented that a significant portion of tuckpointing takes
place at elevated locations on scaffolds and expressed concern about
the control measures listed introducing significant trip and fall
hazards at elevated locations (Document ID 2319, p. 110). Grinding
related to tuckpointing does take place on scaffolds, as evidenced by
one building project evaluated by Cooper et al. where dust collectors
were used on scaffolds to grind mortar from the exterior walls of a 12-
story building (Document ID 4073, Attachment 9l, p. 1). When mortar
grinding will take place on scaffolds, the employer's written exposure
control plan should include procedures to ensure that the dust
collector is operated in an effective and safe manner.
    In the proposed standard, OSHA required personal air purifying
respirators (PAPR) with an APF of 25 to be used while tuckpointing,
regardless of task duration. The proposed requirement was based on high
exposures results, including a TWA measurement of 6,196 [mu]g/m\3\ for
an apprentice mortar grinding with LEV (Document ID 0229, p. 12).
However, it is clear from this NIOSH report that the LEV system was not
fully and properly implemented in that the grinder blade was operated
in a back-and-forth manner with frequent insertions, and the hose from
the tool to the dust collector would frequently kink and fall off.
Based on data in the record, OSHA expects that a worker engaged in
mortar grinding for four hours or less per shift can experience TWA
exposures of less than 500 [micro]g/m\3\, while a worker performing
this task more than four hours per shift could be exposed up to nearly
1,000 [micro]g/m\3\ TWA. Among tuckpointers using LEV outdoors, 40
percent of samples contained in the exposure profile measured exposures
below 50 [micro]g/m\3\, with a mean exposure of 348 [micro]g/m\3\ (see
Section 5.11 of Chapter IV of the FEA). Therefore, Table 1 of the final
standard is requiring the use of respiratory protection with a minimum
APF of 10 for work lasting four hours or less in a shift, which is
reduced from the proposed APF of 25. Based on the evidence of
continuing improvements in the effectiveness of LEV as reported in the
literature, the exposure information, and the requirement in paragraph
(c)(2)(i) to provide a means of exhaust as needed to minimize the
accumulation of visible airborne dust indoors, OSHA concludes that the
reduction to an APF of 10 is appropriate for tasks of four hours or
less in duration. For work lasting more than four hours per shift, OSHA
is maintaining the requirement to use respiratory protection with a
minimum APF of 25.
    Handheld grinders for uses other than mortar removal. Handheld
grinders are tools fitted with rotating abrasive grinding blades,
discs, or small drums used to smooth, roughen, or reshape concrete
surfaces (including forming recesses or slots) (see Section 5.11 of
Chapter IV of the FEA). Grinders may also be used to remove thin layers
of concrete and surface coatings (e.g., performing small-scale spot
milling, scarifying, scabbling and needle-gunning). A grinder typically
has two handles that can form various angles with each other and are
connected to a rotating blade located between them. The worker
typically holds one handle in each hand, forming an angle allowing the
worker to press the rotating blade against the work surface and abrade
the surface and remove the layer of target material (Document ID 4073,
Attachment 4a, Row 91).
    Paragraph (c)(1)(xii) of the standard for construction specifies
two control options. The first control option, which applies only when
grinders are used outdoors, is to use a grinder equipped with an
integrated water delivery system that continuously feeds water to the
grinding surface. When employers choose to use wet grinders indoors or
in an enclosed area, they must comply with the requirements of
paragraph (d) of the final rule. The second option is to use a dust
collector equipped with a commercially available shroud and dust
collection system. The dust collector must provide 25 cfm or greater of
air flow per inch of wheel diameter and have a filter with a 99 percent
or greater efficiency and a cyclonic pre-separator or filter-cleaning
mechanism. OSHA is requiring that the control must be operated and
maintained in accordance with manufacturer's instructions to minimize
dust emissions. The second option is identical to the option required
for handheld grinders used for mortar removal.
    In the proposed standard, OSHA did not specify that the water
delivery system be integrated with the grinder. However, OSHA has
determined that systems that are designed and developed in conjunction
with the tool are more likely to control dust emissions effectively by
applying water at the appropriate rate and dust emission points based
on tool configuration. Further, integrated systems will not interfere
with other tool components or safety devices. These include free-
flowing water systems designed for blade cooling as well as
manufacturers' systems designed for dust suppression alone. OSHA is not
specifying a minimum flow rate, but rather anticipates that the water
flow rates specified by the manufacturer will optimize dust reduction.
OSHA also recognizes that using makeshift water delivery systems can
pose hazards. PTI commented that the use of a water feeding system not
specified by the tool manufacturer could result in serious personal
injury and electric shock for tools that are electrically operated
(Document ID 1973, p. 1). Due to the potential hazards from using a
water delivery system not specified by the manufacturer, and to ensure
the effectiveness of the system in controlling dust, OSHA has modified
Table 1 to require use of integrated water systems that are operated
and maintained according to manufacturer's instructions to minimize
dust emissions.
    OSHA received a number of comments related to the use of wet
methods as a control for handheld grinders. SMI and CISC commented on
the difficulties of using an integrated water system while grinding,
arguing that there is a lack of options with both safety guards and
water supply, that grinders equipped with a water delivery system are
designed to cool the blade rather than control the dust, and that the
dust mitigation effects of the water are speculative (Document ID 2316,
p. 2; 2320, p. 10). However, NIOSH reported that ``several
manufacturers of smaller grinders do offer electric grinders with

integrated water supply capability'' and included the catalog of such
suppliers (Document ID 4233, Attachment 1, pp. 7-8; 3998, Attachment
10). Studies by Linch et al. (2002), Akbar-Khanzadeh (2007, 2010), and
Simcox et al. (1999) evaluated the use of wet methods during grinding
(Document ID 0784; 0552; 3609; 1146). Although there were some
differences in the effectiveness of systems tested by these
investigators, all of them reduced dust levels substantially compared
to dry grinding. Therefore the ability of water to control dust when
grinding is not speculative and has been demonstrated in various
studies throughout OSHA's technological feasibility analysis contained
in Chapter IV of the FEA. In short, OSHA concludes that, based on the
best available evidence, there are commercially available grinders with
integrated water supply capability, and that wet methods can be an
effective control for grinding in many circumstances (Document ID 0522,
p. 778; 1146, pp. 578-579).
    Francisco Trujillo of Miller and Long commented that wet methods
often present significant slip and fall hazards and that attempting to
apply wet methods to any non-horizontal surface has proven ineffective
and often hazardous when using grinders (Document ID 2345, p. 2).
Similarly, Stuart Sessions, an economist testifying on behalf of CISC,
noted that it is difficult to use wet methods in winter in locations
where the water may freeze (Document ID 3580, Tr. 1322). OSHA
acknowledges that not every control option is practical in every
situation, and in such situations, Table 1 of the final standard
permits use of LEV systems to control dust. However, OSHA concludes
that wet methods represent a feasible and effective option outdoors.
    Those who do not implement the wet methods described above, or
those grinding indoors, have the option to use a dust collector
equipped with a commercially available shroud and dust collection
system. Several rulemaking participants testified on the commercial
availability of such equipment, including Gerry Scarano, Executive Vice
President of BAC, Deven Johnson, director of training, health and
safety for the Operative Plasterers and Cement Masons International
Association, and Francisco Trujillo of Miller and Long (Document ID
3581, Tr. 1562, 1592-1593; 3585, Tr. 2962-2964). The record shows that