Will blasting be necessary during this project?
Yes, controlled blasting will be used in specific areas to remove rock during
construction of the Yellow River WRF modernization project. Blasting is safely
used daily in construction throughout the world. It is the most cost-effective
method for breaking rock and helps lower costs to the owners, taxpayers, businesses
and contractors. Rock excavation by blasting takes a fraction of the time required
by conventional earth-moving equipment, so reduces the time span for construction.
What happens during a blast?
Although people often envision dramatic images, most blasts are actually relatively
low-key. More than 90% of the explosive’s energy is used in breaking
the rock. The rest of the energy goes into the ground or air as vibrations
and noise. The ground vibrations travel outward and away from the blast in
the same way that dropping a pebble in a pond of water generates ripples.
These vibrations cannot be seen but may be felt. The vibrations decrease
as they travel away from the energy source, and are about the height of the
thickness of a single sheet of paper by the time they reach neighboring structures.
Underground structures (wells, pools, pipelines and septic tanks) are even
less likely to be affected by vibrations than above ground structures.
How do people respond to a blast?
The response of individuals to blasting vibration will vary from person to
person. Some people can feel extremely low levels of vibration, which are
many times lower than those required to damage a structure. In fact, people
are more sensitive to vibrations than are the structures they occupy. The
vibrations will be felt less when one is outside rather than inside, standing
rather than sitting or lying down. If you are talking, walking or busy around
the house, the vibration will be less noticeable than if you are sitting
with a cup of coffee. Vibrations that are accompanied by noise will appear
to be stronger than the same vibration would be without noise. Human activities
such as walking, door slamming, closing windows or children running through
the house can stress individual building components more so than safe blasting
levels.
How will the blasting be monitored?
The only accurate method to measure vibration intensity is with a seismograph
used to measure vibrations from blasting to make sure they remain within
specified limits. Seismographs will be placed at locations close to the blast
in order to provide measurements that indicate the severity of the blast
and which allow for adjustments to be made in future blasts if necessary.
The results obtained from the seismographs may be used to estimate the severity
of the vibrations at locations further away.
How are blasting activities regulated in Georgia?
The Georgia Blasting Standards Act regulates blasting operations. Gwinnett
County DWR requires that contractors fully comply with this Act. The Act
specifies limits on the severity of vibrations at your home caused by blasting.
You may view these regulations at http://www.ganet.org/cgi-bin/pub/ocode/ocgsearch?number=25-8-1,
or use the contact information at the bottom of this Fact Sheet to obtain
a copy by mail.
What assurance do I have that my home will be protected during blasting?
The construction contractors are required to have a pre-blast survey done by
a qualified technician furnished by the insurance underwriter. The pre-blast
survey documents by notes and photographs the condition of structures within
500 feet of the site perimeter, prior to any blasting occurring. If a property
owner reports damage, then a post-blast survey will be conducted of the reported
damage and will be compared to the pre-blast survey.
If the analysis shows that the blasting did damage my home, how will I be
reimbursed?
This process will work through the individual contractor’s insurance
providers and will depend on their claims procedures. DWR will impress upon
all contractors the importance of getting such matters processed quickly and
efficiently.
Will I be notified prior to blasting work beginning?
Before any blasting work begins, specific neighborhoods will be notified of
the general timeframe that blasting will be ongoing. In cases where pre-blast
surveys are provided, this will be in the form of a certified letter a week
or more in advance. Door hangers may also be used at times, and information
will be posted on the project website, www.yellowriverwrf.com.
Who can I contact if I have additional questions?
Ken Fraker is DWR’s project manager, and you may reach him at 678-318-2404
or Kenneth.Fraker@gwinnettcounty.com.
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