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iii iiiiiiiiiiiu iii • • <br />interoffice <br />M E M O R A N D U M <br />to: Erica Crosby <br />from: Larry Routten <br />subject: Seneca II-W, MR-44 <br />date: March 6, 1998 <br />I reviewed the ground vibration predictions submitted by SCC with their request to blast within <br />500 feet of the oil well which sits in the middle of the mining area. SCC had Matheson Mining <br />Consultants derive scaled distance factors from seismographic analyses of blasts which were <br />conducted in the azea of the well. They submitted a scaled distance factor and maximum allowed <br />explosive weights which are predicted to keep ground vibrations below 5 inches per second. <br />This is the limit approved in the mine permit and appears to be a conservative limit, based on <br />Bureau of Mines studies and the opinions of Matheson and Mike Rosenthal at OSM. I <br />recommend MR-44 be approved. <br />I attempted to duplicate Matheson's results with two different regression analyses, in addition to <br />the one they performed. I was unable to duplicate their results. However, their results are more <br />conservative than mine (i.e., my analyses would allow the use of more explosives than <br />Matheson's results allow). I will continue to try to find where the discrepancy between our <br />analyses occurred. Meanwhile, there is no reason to delay approval of SCC's blasting plans any <br />further. <br />Please stay in contact with SCC to verify that they contact the owners of the well prior to <br />blasting, as they indicated would be done in the revised permit pages. You might also want to <br />verify that the present blaster is familiar with and follows the alternate stemming requirements <br />discussed in the permit if thick layers of mud are encountered while drilling blast holes. <br />030698 <br />