Md. Code Regs. 26.21.01.22

Current through Register Vol. 51, No. 22, November 1, 2024

Section 26.21.01.22 - Ground Vibration

A. Maximum Blasting Limitation.

(1) Blasting near any dwelling, public building, school, church, commercial, or institutional building, or any other structure shall be in accordance with §B of this regulation and Regulation .23 of this chapter.

(2) The maximum peak particle velocity of any blasting operation may not exceed 2 inches per second, measured on the ground adjacent to the nearest structure of concern, unless otherwise directed by the Department. The nearest structure of concern shall be located outside of the permit area, and may not be under the ownership or control of the permittee.

(3) The Department may require the permittee to reduce the peak particle velocity if it determines that a lower standard is required to protect property outside the permitted area, and not under the permittee's ownership or control, or to protect public safety because of sensitive conditions relating to density of population, land use, age or type of structure, geology or hydrology of the area, frequency of blasts, or other factors.

(4) The maximum peak particle velocity of ground motion does not apply to property inside the permit boundary.

(5) The standards included in this regulation are intended to protect conventional low-rise structures such as homes and schools. Engineered structures may safely withstand higher vibration levels and, based upon an approved engineering study, the Department may allow higher vibration levels for engineered structures.

B. Monitoring Ground Vibration.

(1) Monitoring Methods.

(a) The permittee shall select a method described in Regulation .24B, Table I, Table II, or Graph I, and use it in accordance with this regulation, or use a response spectra analysis to monitor ground vibration resulting from blasting.

(b) If the permittee uses Table I, the permittee shall submit information to the Department for approval under §A(2) of this regulation.

(c) The permittee may select a method described in Table II or Graph I, or use a response spectra analysis without approval by the Department.

(d) The order of methods in increasing sophistication are charge weight per delay versus distance (Table I), distance versus peak particle velocity (Table II), peak particle velocity versus frequency (Graph I), or response spectra analysis.

(2) Table I Use.

(a) Table I applies to ground vibration limits for blasting which the Department does not require to be measured with approved seismic instrumentation.

(b) The maximum amount of explosives per delay may not exceed the limits in Table I.

(c) The amount of explosives per delay may not exceed 520 pounds in any 8 millisecond or greater delay period.

(d) The Department may approve the use of Table I at a particular site upon request of the permittee, but may request seismographic records of test blasting at the site and other information requested by the Department.

(e) The Department may not approve the use of Table I if the peak particle velocity of 2 inches per second will be exceeded.

(3) Table II or Graph I Use.

(a) Table II or Graph I shall be used when the Department determines that blasting is to be monitored by a seismic instrument or system of instrumentation approved by the Department.

(b) Blasting measured in accordance with Table II shall be conducted so that the peak particle velocity on any one component of an instrument measuring the 3 mutually perpendicular components of motion does not exceed the limits of the table.

(c) Seismic instruments that monitor blasting in accordance with Table II shall have the instrument's transducer firmly coupled to the ground.

(d) Blasting measured in accordance with Graph I shall be conducted so that the continuously variable particle velocity criteria versus frequency criteria is not exceeded.

(4) If response spectra analysis is selected by the permittee, it shall be used to determine that blasting vibrations are controlled so that a relative velocity of 1.5 inches per second is not exceeded (within the 4-----12 hertz range of natural frequencies for low rise structures).

Md. Code Regs. 26.21.01.22