Virginia Law

(a) General requirements. Blasting shall be conducted 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 ground water outside the permit area.

(b) Airblast.

(1) Limits.

(i) Airblast shall 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 Paragraph (e) of this section.

(ii) If necessary to prevent damage, the division may specify lower maximum allowable airblast levels than those of Paragraph (b)(1)(i) of this section for use in the vicinity of a specific blasting operation.

(2) Monitoring.

(i) The permittee shall conduct periodic monitoring to ensure compliance with the airblast standards. The division may require airblast measurement of any or all blasts and may specify the locations at which such measurements are taken.

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

(c) Flyrock. Flyrock traveling in the air or along the ground shall not be cast from the blasting site-

(1) More than one-half the distance to the nearest dwelling or other occupied structure;

(2) Beyond the area of control required under 4VAC25-130-817.66(c); or

(3) Beyond the permit boundary.

(d) Ground vibration.

(1) General. In all blasting operations, except as otherwise authorized in Paragraph (e) of this section, the maximum ground vibration shall not exceed the values approved by the division. The maximum ground vibration for protected structures listed in Paragraph (d)(2)(i) of this section shall be established in accordance with either the maximum peak-particle- velocity limits of Paragraph (d)(2), the scaled-distance equation of Paragraph (d)(3), the blasting-level chart of Paragraph (d)(4), or by the division under Paragraph (d)(5) of this section. All structures in the vicinity of the blasting area, not listed in Paragraph (d)(2)(i) of this section, 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 permittee and approved by the division before the initiation of blasting.

(2) Maximum peak-particle velocity.

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

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

(3) Scaled-distance equation.

(i) The permittee may use the scaled-distance equation, W=(D/Ds)², 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 division using the values for scaled-distance factor listed in Paragraph (d)(2)(i) of this section.

(ii) The development of a modified scaled-distance factor may be authorized by the division on receipt of a written request by the permittee, supported by seismographic records of blasting at the minesite. The modified scaled-distance factor shall be determined such that the particle velocity of the predicted ground vibration will not exceed the prescribed maximum allowable peak particle velocity of Paragraph (d)(2)(i) of this section, at a 95-percent confidence level.

(4) Blasting-level chart.

(i) The permittee may use the ground vibration limits in Figure 1 to determine the maximum allowable ground vibration.

(ii) 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 the analysis of the predominant frequency contained in the blasting records shall be approved by the division before application of this alternative blasting criterion.

(5) The maximum allowable ground vibration shall be reduced by the division below the limits otherwise provided by this section, if determined necessary to provide damage protection.

(6) The division may require the permittee 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 measurement.

(e) The maximum airblast and ground-vibration standards of Paragraphs (b) and (d) of this section 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 division before blasting.