(a) All blasting shall be conducted during daytime hours, between sunrise and sunset; provided, that the Engineer may specify a more restrictive time period based on public requests or other consideration, including the proximity to residential areas. No blasting shall be conducted on Sunday, provided, however, that the Engineer may grant approval of a request for Sunday blasting if the operator demonstrates to the satisfaction of the Engineer that the blasting is necessary and there has been an opportunity for a public hearing. Blasting shall not be conducted at times different from those announced in the blasting schedule except in emergency situations where rain, lightning or other atmospheric conditions, or the operator or public safety requires unscheduled detonations. Blasting shall be conducted in such a way so as to prevent injury to persons, damage to public or private property outside the permit area, adverse impacts on any underground mine, and change in the course channel, or availability of surface or groundwater outside the permit area.
(b) Safety Precautions.
(1) Three minutes prior to blasting, a warning signal audible to a range of one-half mile from the blast site will be given. This preblast warning shall consist of three short warning signals of five seconds duration with five seconds between each signal. One long warning signal of twenty seconds duration shall be the “all clear” signal. Each person in the permit area, and each person who resides or regularly works within one- half mile of the permit area shall be notified of the meaning of these signals;
(2) All approaches to the blast area shall be guarded against unauthorized entry prior to and immediately after blasting;
(3) All charged holes shall be guarded and posted against unauthorized entry; and
(4) The certified blaster shall be accompanied by at least one other person at the time of firing of the blast.
(c) Airblast Limits.
(1) Airblast shall not exceed the maximum limits listed below at the location of any dwelling, public buildings, school, church or community or institutional building outside the permit area.
Lower Frequency of Measuring System in Hz (*3 dB) | Maximum Level, in dB |
0.1 Hz or lower – flat response 1 | 134 peak |
2 Hz or lower – flat response | 133 peak |
6 Hz or lower – flat response | 129 peak |
1 only when approved by the City Engineer | |
C-weighted – slow response2 | 105 peak dBC |
2 Only when approved by the City Engineer. | |
(2) If necessary to prevent damage, the Engineer may specify lower maximum allowable airblast levels for use in the vicinity of a specific blasting operation.
(3) Monitoring. The operator shall conduct periodic monitoring to ensure compliance with the airblast standards. The Engineer may require airblast measurement of any or all blasts and may specify the locations at which such measurements are taken. The air blast measuring system used shall have an upper-end flat-frequency response of at least 200 Hz.
(d) Flyrock, including blasted material, shall not be casst from the blasting site more than halfway to the nearest dwelling or other occupied structure, beyond the area of control specified in paragraph (e) of this subsection, or in no case beyond the bounds of the permit area.
(e) Access to the blast area shall be controlled against the entrance of livestock or unauthorized personnel during blasting and for a period thereafter until an authorized person has reasonably determined:
(1) That no unusual circumstances exist such as imminent slides or undetonated charges, etc.; and
(2) That access to and travel in or through the area can be safely resumed.
(f) At the request of the Engineer, the operator shall monitor air blast levels using an instrument with an upper-end flat-frequency response of at least 200 Hz.
(g) Blast Design.
(1) An anticipated blast design shall be submitted if blasting operations will be conducted within:
A. 1,000 feet of any building used as a dwelling, public building, school, church or community or institutional building outside the permit area; or
B. 500 feet of an active or abandoned underground mine.
(2) The blast design may be presented as part of a permit application or at a time before the blast, as approved by the Engineer.
(3) The blast design shall contain sketches of the drill patterns, delay periods, and decking, and shall indicate the type and amount of explosives to be used, critical dimensions, and the location and general description of structures, including protected structures, to be protected, as well as a discussion of design factors to be used, which protect the public and meet the applicable airblast, flyrock, and ground-vibration standards.
(4) The blast design shall be prepared and designed by a certified blaster.
(5) The Engineer may require changes to the design submitted.
(h) The Engineer may prohibit blasting on specific areas where it is deemed necessary for the protection of public or private property or the general welfare and safety of the public.
(1) The operator may use the following scaled distance formulas to determine the allowable maximum weight of explosives (lbs.) to be donated in any eight millisecond period without seismic monitoring:
Formula | Distance in Feet From the Blasting Site to the Nearest Protected Structure |
W = (D/50)2 | 0 - 300 feet |
W = (D/55)2 | 301 - 5,000 feet |
W = (D/65)2 | 5,001 feet or greater |
W = Weight of explosives in pounds
D = Distance to the nearest structure
(j) The scaled distance formulas need not be used if a seismograph measurement at the nearest protected structure is recorded and maintained for every blast. The peak particle velocity in inches per second in any one of the three mutually perpendicular directions shall not exceed the following value at any protected structure:
Seismograph Measurement | Distance to Nearest Protected Structure |
1.25 | 0 - 300 feet |
1.0 | 301 - 5000 feet |
0.75 | 5,001 feet or greater |
(k) The Engineer may require a seismograph recording of any or all blasts based on the physical conditions of the site in order to prevent injury to persons or damage to property.
(l) The maximum allowable ground vibration as provided in subsections (i) and (j) hereof shall be reduced by the Engineer, if determined necessary to provide damage protection.
(m) The maximum airblast and ground-vibration standards of subsections (c) and (j) hereof shall not apply at the following locations:
(1) At structures owned by the permittee and not leased to another person.
(2) At structures owned by the permittee and leased to another person, if a written waiver by the lessee is submitted to the Engineer before blasting.
(Ord. 1941. Passed 2-19-98.)
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