Md. Code Regs. 26.20.22.06

Current through Register Vol. 51, No. 19, September 20, 2024

Section 26.20.22.06 - Surface Blasting Requirements

A. All blasting shall be conducted between sunrise and sunset.

B. Blasting shall be conducted at times approved by the Bureau and announced in the published blasting schedule. The Bureau may limit the area covered, specify more restrictive time periods, and limit the sequence of blasting as listed in the schedule, if the limitations are necessary or reasonable in order to protect the public health and safety or welfare.

C. Unscheduled blasts may be conducted only when public or permittee health and safety so require and for emergency blasting actions. When an unscheduled blast is conducted, the permittee shall:

(1) Using audible signals, notify residents within 1/2 mile of the blasting site;

(2) Orally notify residents within 1,000 feet of the blasting site and the Bureau;

(3) File a complete written report of the unscheduled blasting with the Bureau not later than 3 days after the unscheduled blast; the report shall include a detailed description of the reasons for the unscheduled blast, including reasons why the blast could not have been delayed until the next day, the actual time the blast was conducted, the warning notices that were given, and a copy of the blasting record.

D. Warning and all-clear signals of different character that are audible within a range of 1/2 mile from the point of the blast shall be given. Each person within the permit area and each person who resides or regularly works within 1/2 mile of the permit area shall be notified of the meaning of the signals in the blasting schedule.

E. Access to an area subject to flyrock from blasting shall be regulated to protect the public and livestock. Access to the area shall be controlled to prevent the presence of livestock or unauthorized personnel during blasting and until an authorized representative of the permittee has reasonably determined that:

(1) No unusual circumstances, such as imminent slides or undetonated charges exist; and

(2) Access to and travel in or through the area can be safely resumed.

F. Blasting shall be conducted to prevent injury to persons, damage to public or private property outside the permit area, adverse impacts on underground mines and change in the course, channel, or availability of ground or surface waters outside the permit area.

G. Except where lesser distances are approved by the Bureau based upon a pre-blasting survey, seismographic investigation, or other appropriate investigation, blasting may not be conducted within:

(1) Three hundred feet of any building used as a dwelling, school, church, hospital, or nursing facility; and

(2) Five hundred feet of facilities including, but not limited to, disposal wells, petroleum or gas-storage facilities, municipal water-storage facilities, fluid-transmission pipelines, gas or oil-collection lines, or water and sewage lines.

H. Airblast.

(1) Limits.

(a) An airblast may not exceed the maximum limits listed below at the location of any dwelling, public building, school, church, or community or institutional building outside the permit area except as provided in §K of this regulation:

Lower frequency limit of measuring system in Hz (± 3 dB)	Maximum level in dB
0.1 Hz or lower-flat response¹	134 peak
2 Hz or lower-flat response	133 peak
6 Hz or lower-flat response	129 peak
C-weighted, slow response¹	105 peak dBC

¹Only when approved by the Bureau.

(b) If necessary to prevent damage, the Bureau may specify lower maximum allowable airblast levels than those of §H(1)(a) of this regulation for use in the vicinity of a specific blasting operation.

(2) Monitoring.

(a) The operator shall conduct periodic monitoring to ensure compliance with the airblast standards. The Bureau may require airblast measurement of any or all blasts and may specify the location at which the measurements are taken.

(b) The measuring systems shall have an upper end flat-frequency response of at least 200 Hz.

I. Flyrock, including blasted material traveling along the ground, may not be cast more than half the distance from the blasting vicinity to the nearest dwelling or other occupied structure beyond the area of regulated access under §E of this regulation, or beyond the permit boundary.

J. Ground Vibration.

(1) In all blasting operations, except as otherwise authorized in §K of this regulation, the maximum ground vibration may not exceed the values approved in the blasting plan required under COMAR 26.20.02.13 a F. The maximum ground vibration for protected structures listed in §J(2)(a) of this regulation shall be established in accordance with either the maximum peak-particle-velocity limits of §J(2), the scaled-distance equation of §J(3), or by the Bureau of Mines under §J(4) of this regulation. All structures in the vicinity of the blasting area, not listed in §J(2)(a) of this regulation, such as water towers, pipelines, and other utilities, tunnels, dams, impoundments and underground mines shall be protected from damage by establishment of a maximum allowable limit on the ground vibration, submitted by the operator of the blasting plan, and approved by the Bureau of Mines.

(2) Maximum Peak Particle Velocity.

(a) The maximum ground vibration may not exceed the following limits at the location of any dwelling, public building, school, church, or community or institutional building outside the permit:

Distance (D) from the blasting site, in feet	Maximum allowable peak particle velocity (V max) for ground in inches/second2
0 to 300	1.25
301 to 5,000	1.00
5,001 and beyond	0.75

²Ground vibration shall be measured as the particle velocity. Particle velocity shall be recorded in three mutually perpendicular directions. The maximum allowable peak particle velocity shall apply to each of the three measurements.

(b) A seismographic record shall be provided for each blast.

(3) Scaled-Distance Equation.

(a) An operator may use the scaled-distance equation, W = (D/Ds)B., to determine the allowable charge weight of explosives to be detonated in any 8-millisecond period, without seismic monitoring, where W = the maximum weight of explosives, in pounds, D = the distance, in feet, from the blasting site to the nearest protected structure, and Ds = the scaled-distance factor, which may initially be approved by the Bureau using the values for scaled-distance factor listed in the following chart:

Distance (D) from the blasting site, in feet	Scaled-distance factor (Ds)
0 to 300	50
301 to 5,000	55
5,001 and beyond	65

(b) For distances between 100 and 5,000 feet, solution of the equation results in the following maximum weight:

Distance in feet (D)	Maximum weight in pounds (W)
100	4
200	16
300	36
400	53
500	83
600	119
700	162
800	212
900	268
1000	331
1100	400
1200	476
1300	559
1400	648
1500	744
1600	846
1700	955
1800	1071
1900	1193
2000	1322
2500	2066
3000	2975
3500	4050
4000	5289
4500	6694
5000	8264

(c) The development of a modified scale-distance factor may be authorized by the Bureau on receipt of a written request by the operator, supported by seismographic records of blasting at the minesite. The modified scale-distance factor shall be determined such that the particle velocity of the predicted ground vibration does not exceed the prescribed maximum allowable peak particle velocity of §J(2)(a) of this regulation, at a 95-percent confidence level.

(4) Blasting-Level Chart.

(a) An operator may use the ground vibration limits in Figure 1 to determine the maximum allowable ground vibration.

Click here to view Image

(b) If the Figure 1 limits are used, a seismographic record including both particle velocity and vibration frequency levels shall be provided for each blast. The method for analysis of the predominant frequency contained in the blasting records shall be approved by the Bureau before application of this alternative blasting criterion.

(5) The maximum allowable ground vibration shall be reduced by the Bureau to less than the limits otherwise provided by this regulation, if determined necessary to provide damage protection.

(6) The Bureau may require an operator to conduct seismic monitoring of any or all blasts and may specify the location at which the measurements are taken and the degree of detail necessary in the measurements.

K. Exemptions to Certain Standards. The maximum airblast and ground-vibration standards of §§H and J of this regulation may 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 regulatory authority before blasting.

L. Blasting operations within 500 feet of active underground mines require approval of the Bureau and federal regulatory authorities concerned with the health and safety of underground miners.

Md. Code Regs. 26.20.22.06

Regulations .06 were previously codified as COMAR 08.13.09.25 a A_H, respectively. Recodification occurred in April, 1993. For a history of these regulations before April, 1993, see "Administrative History of COMAR 08.13.09 before April, 1993" which follows COMAR 26.20.01.