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~ ~ activity Mining does have some adverse effects, and the annoyance that dei.ives from those effects is genuinely regretted. One cannot build highways and bridges or ne~a developments or, for [hat natter, permit and operate mines without causing annoyance to some. These are all legal and even desirable activities, benefiting the rt+aJo'rity of the people, and are sometimes essential to all of us. Cp:rtainly we are all dependent on nun future energy supplies, and Fzrhaps coal is even a more acceptable source of energy to most people than nuclear sources aze. Some of this coal mining activity will cause annoyance. But with care and understanding, one can at least try to remove some of the sharpest edges from that annoyance. ACTUAL BIAST DAMAGE CRITERIA The Bureau .of Mines research on blast vibration damage is detailed and extensive. Prang the conclusions drawn by RI 8507 (see page 29 of this manual for this document's definition of threshold damage due to blast produced ground vibration) aze the"following: Home construction is also a factor in the minuaan expected damage levels. G~psumboard (Drywall) interior walls are more damage resistant than older, plaster on wood lath construction. r Practical, safe criteria for blasts that generate low-frequency ground ground vibrations aze 0.75 t in/sec for modern gypsumboard houses and 0.50 .-~~ in/sec for plaster on lath interiors. For ~~ frequencies above 40 Fiz, a safe particle velocity' ~~; g maximum of 2.0 in/sec is recommended for all houses. ~~ All homes eventually crack because of a vaziety of ~'~* environmental stresses, including humidity and ~'. temperature changes, settlement from consolidation and _:~: variations in ground moisture, wind and even water ,;~ absorption from tree roots. Consequently there may be '~. no absolute mininnrm damage threshold when the vibration ,°°" (from any cause, for instance slamming a door) could in sore case precipitate a crack about to occur. y~" a Hunan reactions to blasting can be the limiting factor. Vibration levels can be felt [hat aze ~~' considerably lower than those required to produce .>~F' `_i' damage. Human reaction to vibration is dependent on event duration as well as level. Pazticle velocities of 0.5 inlsec ( 1-sec vibration) should be ~~' tolerable to about 95 pct of the people perceiving it .}~ as "distinctly perceptible". .:;. 120 -_ `., : ~~° - ~, ,,.~,.