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Blasung tmpactr. and Rock Slope Stability Assesanciii: for Cottonwood [hsarry to Gland County. CO <br />Historical NYC Vibration Data Plot <br />0.01 <br />L,Tralt,0s) t 14 <br />O�u <br />f 1 i l l 1 1 1 1 1 i'1 ITI <br />Scaled Distance <br />e %.arnLv <br />■ Con -Ed <br />A Hunter <br />I"igurc 3,4 Historical NYC Scaled Distance --M Data from Blasling at Carnegie Hall. the Cron -lesson Shaft at <br />3e Street and I' Avenue and foundation blasting at Hunter College at between 38"' and 390 Starts (NOTE- the <br />95wp curve n>rans that 95 percent of the time, predicted values will he lower than the value calculated) <br />When site-specific historical data is not available, the K factor value can be estimated based on <br />physical rock properties and degree of blast confincmcnt_ E rom the author's past experience, for <br />blasts in the igneous rock formations at the Cottonwood site, a prediction equation with a h <br />factor of 240 can be used to predict vibration intensities (PPV) at various locations of concern. <br />With this cautiously high K -factor, predicted levels of vibration will likely be higher than actual <br />values measured at similar scaled distances. The resulting prediction equation, which is used in <br />the site-specific evaluations in Section 4 of this report, is shown Equation 3.3 below. <br />PPT = 240(DI W) t .6 Equation 3.3 <br />3.6 Human Response to Transient Vibrations <br />In addition to concerns about vibration damage. under certain conditions, humans and animals <br />can be startled or annoyed by blast -induced ground vibration. Research has also shown that the <br />human response to transient vibration --like those caused by blasting --varies depending on <br />exposure time and the intensity of the motion. Response curves defining how humans respond to <br />transient vibrations based on these variables are shown in Figure 3.5. <br />REVhY Associates, Inc Page 10 April 2004 <br />