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Impacts of Mechanical Equipment at Benson Brothers Quarry on Nearby Rock Bluffs included a portable jaw and cone rock crasher, Caterpillar 350 backhoe and a 750C John Deere bulldozer. Measurements were made on hard-packed sedimentary rock surfaces where vibration levels would be similar to those at the Red Shale quarry. This report includes analyses of the vibration measurement data and evaluations of expected impacts on adjacent rock faces and soil slopes. Actual vibration measurement data reports including summaries of vibration intensities, dominant frequencies of motion, and motion-time plots are include in Attachment I. In order to acquaint the reader with the terms and physical science of ground motion, this also includes a brief summary of this subject. 2.0 PHYSICAL CHARACTERISTICS OF GROUND VIBRATIONS When mechanical equipment is used to excavate rock, dynamic forces are applied to the ground. These forces create transient stress waves that spread through the body of ground mass and along the ground surface. As stress waves move through ground and rock, particles of the ground respond by oscillating or moving very short distances that are much less than the thickness of a human hair (0.008 in). If the energy source is continuous like that caused by crashers, the ground motion will also be continuous or "steady-state. It is important to know that vibrations of this type create "elastic" motion in ground, which means the vibrating ground particles return to their original positions when the vibration stops. In other words, there is no permanent displacement or movement. The physical nature of vibrating ground motion can be measured in several ways. These measures include: • Particle displacement • Particle velocity • Particle acceleration • Vibration frequency Displacement is a measure of ground particle travel distance or location with respect to time. Particle velocity measures the speed of movement and acceleration is the rate of velocity changes. Vibration frequency is a measure of how many oscillations a Bound particle makes per second of time. Frequency is reported in units of Hertz (Hz), which is equivalent to cycles per second. As shown in Figure 3, when measured ground motion speed is plotted with respect to time, the waveforms aze approximately sinusoidal (look like a sine waves), so elastic ground displacement and acceleration can be estimated using equations 1.1 and 1.2. REVEY Associates, Inc. Page 3 of 7 February 2006