Best Practices for the Reduction of Air Emissions From Construction ...

CHEMINFO
reduce fugitive dust emissions (among many of these
fabrication processes) is the use of high efficiency
particulate arrestors (HEPA). HEPA filters control
fine particulate matter emissions from dry work on
concrete such as blasting, crushing, jack-hammering,
grinding, boring holes, sandblasting, polishing, and
sawing. HEPA filters can capture 95% of silica dust.
Enclosures should also be used whenever possible as
they are an effective way to prevent the transport of
dust throughout buildings and from buildings to the
environment. Wood frame and plastic film
enclosures can be designed with negative pressure to
ensure that dust does not flow out of the enclosed
space. The potential of increased workplace exposure
to dust must be considered when utilizing enclosures
inside structures.
Ducting systems should be cut-off to prevent the
circulation of dust during construction and
renovation activities.
Material drop heights for building debris should be
minimized whenever possible. When debris is being
dropped from high levels, this material should be
dropped over several sequential stages instead of the
entire distance at once. Chutes that are used to drop
materials to the ground level should be enclosed, if
feasible. In addition, bins that are used to receive
materials should also be covered when not in use.
6.6.1 Cutting, Grinding and Drilling
Work practices to minimize fugitive dust emissions
from various cutting, grinding and drilling
operations include the following:
• Use prefabricated materials whenever possible,
to avoid the necessity of using these processes on
the construction site;
• Apply water sprays in conjunction with cutting
equipment;
• Avoid cutting out errors and re-bars;
• Always try to fill whenever possible rather than
cutting back oversized work;
• Always use dust extraction/minimization
systems with angle grinders and disc cutters;
• When cutting roadways, pavements, blocks, etc.,
a diamond bladed floor saw with water pumped
through the system should be used; and
• When raking out mortar/pointing, a mortar
raking kit, fitted on to a standard 5 inch (13
centimeter) angle grinder can be used on soft
mortar. For hard mortar, a super-saw with
oscillating blades can be used.
6.6.1.1 Design Considerations to Avoid Grinding
and Cutting
If possible cutting and grinding should be avoided
through the design and other techniques, such as:
• Designing tolerances for infilling rather than
cutting back oversize work;
• Increasing the size of concrete pours to reduce
the need for grinding;
• Use of bonding agents;
• Designing the concrete components themselves
to affect interfaces; and
• Using wet grit blasting for outside work.
Should grinding be necessary, PM emissions can be
mitigated by: (i) fitting tools with dust bags; (ii) prewashing
work surfaces; (iii) screening off areas to be
ground; and (iv) vacuuming up, as opposed to
sweeping away, residual dust.
6.6.2 Sand and Grit Blasting and Façade
Cleaning
6.6.2.1 Utilize Wet or Other Processes That
Minimize Dust Generation
When sand, grit or shot blasting or façade cleaning,
wet processes (e.g., high pressure water blasting or
water blasting supplemented by abrasives) should be
used whenever possible. Wet processes introduce
water into the air/grit stream, which reduces dust
generation. In addition, it should be ensured that the
slurries do not dry out. Spent abrasive materials
should be wetted and periodically removed from the
job site. Hydroblasting, vacuum blasting and
centrifugal wheel blasting are also alternatives that
reduce fugitive dust generation vs. dry blasting.
6.6.2.2 Utilize Enclosures
If dry grit blasting is necessary, then curtains,
enclosures or shrouds should be erected to completely
surround the blasting operation. This includes the
area around and underneath the operation. The
ground cannot be used as the bottom of the enclosure
unless completely covered with plastic sheeting or a
tarpaulin. The enclosure should be constructed of
Best Practices for the Reduction of Air Emissions From Construction and Demolition Activities 24