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Blasting Plaa Variance <br />Rimrock Mine <br />According to Rule 4.08.4(7), it is understood that blasting <br />cannot be conducted within 500 feet of a gas pipeline, unless <br />demonstrations are made showing that lesser distances are safe. <br />The material in this section is included to demonstrate that <br />surface blasting can be conducted up to 50 feet from the Raton <br />Gas pipeline. <br />According to Raton Gas Transmission Co., the pipeline is a welded <br />steel line with a .156 inch wall thickness and a inside diameter <br />of 8-5/8 inches. Joints were arc-welded at lengths of 20 feet and <br />40 feet. The normal pressure rating for this pipe is 1500 psi <br />although the current pressure in the line is only 300 to 400 psi. <br />The line was installed in 1963 and was buried 2.5 feet below the <br />surface. <br />• It is generally accepted that ground vibration (particle <br />velocity) should be limited to 1.0 inches per second for <br />dwellings, public buildings, schools, churches and other <br />community or institutional buildings. There is substantial <br />evidence that welded steel gas pipelines constructed after 1945 <br />are safe at particle velocities of 10 inches per second or more. <br />In general, buried structures such as gas pipelines or waterlines <br />are able to withstand larger ground vibrations than occupied <br />dwellings on the surface. The ability of gas transmission lines <br />to withstand large particle velocities was verified by discussion <br />or documentation with the following parties: <br />1) OSM Denver Office, Hike Rosenthal, blasting expert. <br />2) Vibra - Tech Engineers, Inc., as established blasting <br />and blasting compliance firm with offices nationwide. <br />3) Farrell Cooper Mining Company, a surface mining firm with <br />strip mines in Oklahoma near numerous gas lines. <br />• <br />