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Below is a synopsis of a report on wells and springs. It should be <br />noted that the wells investigated were not cased. Ground <br />vibrations created by blasting are the most severe at the earth's <br />surface. Significant reduction in ground motion is observed with <br />increasing depth. <br />WELLS AND SPRINGS <br />The source of these comments is the USBM study "Survey of Blasting <br />Effects on Ground Water Supplies in Appalachia," Contract No. <br />J-0285029, November, 1980. It should be noted that this study <br />relates to coal mine blasting where large per delay explosive <br />weights exceeding 5000 pounds are common. The USBM study included <br />four test sites chosen for geographic and geologic diversity. <br />Maximum resultant particle velocities of up to 5.44 inches per <br />second were recorded with "no direct evidence of change in water <br />quality or well performance..." <br />The well continues to perform in the same manner although <br />blast induced round vibrations at the surface may <br />approximate 2.0 inches per second maximum resultant <br />particle velocity, until surface mining approaches to <br />within about 300 feet of the water well. <br />• State agencies and coal companies in Appalachia were <br />contacted to develop a list of reportedly blast damaged <br />wells. Of 36 wells so reported, 24 were investigated in <br />the field but there was no clear evidence that the <br />problem was blast related. In most cases, it was evident <br />that other factors were responsible for changes in well <br />behavior. <br />Maximum ground vibration levels at the four test wells, <br />measured as close as practical to the well heads, were <br />2.2, 5.44, 2.14, and .84 inches per second resultant <br />particle velocity. Based on observable change in well <br />conditions immediately after a blast, there was no direct <br />evidence of any significant change as a result of <br />blasting. At three sites, when mining approached within <br />a distance of approximately 300 feet, a fairly abrupt <br />drop in static water level occurred followed by a <br />significant improvement in well performance as indicated <br />by specific capacity. At the fourth site, there was no <br />change. <br />(This paper is available through the National Technical Information <br />Service.) <br /> <br />2 <br />