(a) Monitoring ground vibrations and air overpressure as necessary to ensure that established limits are not exceeded. The monitoring requirements specified herein shall be considered the minimum allowable monitoring effort.
(b) As a minimum, four location of varying distance from the blast area shall be monitored. One constant location at the structure nearest the blast shall be establised. Other monitoring locations shall be on other structures in the immediate vicinity of blasting, and may be moved to address particular concerns that may be raised during the course of the work.
(c) Air overpressure and ground vibrations for every blast shall be monitored, at the structure controlling the blast design, usually the structure nearest the blast.
(d) Monitoring locations may be moved during the course of the work, to better control adverse effects, and to develop a record of ground vibrations at other structures resulting from blasting.
(e) In general, geophones shall be positioned on the ground surface near the structure of concern, but no closer than four feet. If the ground is not exposed at the desired monitoring location, the geophone shall be placed on concrete or asphalt surfaces at approximately the outside ground surface level. The geophone shall be oriented with the directional arrow toward the blast, and level.
(f) Where peak particle accelerations are expected to be less than 0.2 g, spikes or a covering sandbag shall be used to ensure coupling of the geophone to the surface to be monitored.
(g) Where peak particle accelerations are expected to range from 0.2 g to 1.0 g, and the measurement surface consists of soil, the geophone shall be completely buried, or partially buried and sandbagged. Where the measurement surface consists of rock, asphalt or concrete, the geophone shall be fastened to the measurement surface with screws, adhesives or equally secures means.
(h) Where peak particle accelerations are greater than 1.0 g, and the measurement surface consists of soil, the geophone shall be completely buried. Where the measurement surface consists of rock, asphalt or concrete, the geophone shall be fastened to the measurement surface with cement or bolts.
(i) The geophones shall not be placed on plant roots, loose fill, loose slabs, or hollow slabs.
(j) Sound-pressure microphones shall be placed in an area not masked by trees or buildings, at least five feet from the side of any structure, and three to five feet above ground surface.
(k) For each blast detonated, a Monitoring Report shall be submitted within one week, but prior to the next blast in the event that vibration or air overpressure limits are exceeded and shall include the following:
(1) Shot number, date, and firing time;
(2) Name and signature of person performing the monitoring;
(3) Identification of blast monitoring system, and date of calibration;
(4) Specific monitoring locations, indicated by GPS, or northings and eastings and horizontal distance from the blast to the transducers, measured on the ground or scaled from plans.
(5) Measures taken to couple the vibration transducers to the surface to be monitored;
(6) Peak sound pressure level, and peak particle velocity on each three directions, predominant frequency of each, and time of occurrence relative to trigger;
(7) The waveform graph of sound pressure level and particle velocity in each three directions;
(8) A weather condition that may affect sound pressure levels, including wind speed and direction, temperature barometric pressure, and cloud cover.
(Ord. 2005-5-4. Passed 5-3-05.)