Quarry Index:

About the Quarry

Meeting Agendas

Past Meeting Minutess

Definitions

Facts & Questions

Maps & Graphs

About the Reports

Links:
Austin Powder
Hanson Aggregates Servtex
USBM
USBM Criteria (“z” curve chart)
Vibra-Tech

HOW TO UNDERSTAND & READ MONTHLY REPORTS

How to Understand the Monthly Quarry Reports
DATE: self-explanatory
SHOT #: self-explanatory
SHOT LOCATION: self-explanatory
WEATHER: May be important as on cloudy days the intensity of blast may be more noticeable. This can result when air blasts are reflected off the clouds and directed downward rather than radiating in all directions. The downward reflection can increase noise and overpressure readings.
TIME: self-explanatory
PPV (Peak Particle Velocity):
This is the measurement of the vibrations that move through the ground and may be felt as they move below foundations. Federal guidelines indicate that damage can occur at 2.00. To err on the side of safety, federal guidelines have been set at 0.50 which may lengthen existing cracks in plaster and at 0.75 which may lengthen existing cracks in sheetrock. In reference to the latter, damage thresholds may be increased as frequency moves above 11 hertz (Hz).
FREQUENCY (Frequency):
Frequency is important since damage is more likely to occur when it matches that of structures. The natural frequency of single story structures is 6-8 Hz and for multi-story 8-11 Hz. The higher the frequency is, the less the impact.
AIR (dB):
Air overpressure is generally the most noticeable impact on structures. As this air wave (measured in decibels (dB)) contacts structures, it causes walls to vibrate. Up to 128 dB is the federal guidelines safe level. Glass may break between 150-170 dB and structural damage may occur at 180 dB.
MAX LBS/DELAY (maximum pounds of explosives per detonation):
The amount of explosives per detonation. Each blast is comprised of multiple separate detonations each of which are separated by milliseconds (delay). While these blasts are perceived as a single blast, they are actually a series on small blasts. Without these minute separations, a single blast would have an extremely high impact.
DISTANCE FROM BLAST: self-explanatory
SEISMOGRAPH LOCATION: self-explanatory

To see the most recent report go to Maps & Graphs Blast Table by Month

Citizen's Blast Report

Citizen's Blast Report Form

You may complete this PDF form online (using your computer), but you cannot save it with the data. Print the completed form before you close it. After you've printed it, send it to:

City of Garden Ridge
9400 Municipal Parkway
Garden Ridge, TX 78266

Att: Quarry Commission