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RECEIVED <br /> FEB 2 6 2021 <br /> February 19, 2021 DIVISION OF RECLAWTION <br /> MINING AND SAFETY <br /> Re: "Controlled Blast" undertaken by Cemex Cement Lyons Facility on January 29, 2021 at <br /> approximately 1:00 pm <br /> Dear Boulder County Commissioners, <br /> You're aware that residents in the Lyons and St. Wain Valleys felt tremors generated from the <br /> Cemex mine blast on January 29, 2021, and that tremors reported to last as long as 4 seconds <br /> were experienced as far away from Dowe Flats as Apple Valley west of Lyons. <br /> Per the Longmont Times-Call, Cemex reports the blast as a"Controlled Blast" and as one <br /> within its permitted activities. Please note thought that in this case advanced courtesy notice <br /> was NOT provided to the community. <br /> Use of the term "Controlled Blasting" in this case may mislead the average reader. Controlled <br /> blasting is a technical term applied to blasting which involves techniques used to minimize <br /> "overbreak" which means the fracturing of rock beyond the designated boundary of main <br /> excavation area(see Blasters Handbook, 16th ed., 1980, Explosive Products Division, E.I. du <br /> Pont de Nemours&Co., Chapter 22, p. 373.) <br /> In this case, and regardless of the use of the term "Controlled Blast," community members <br /> experienced seismic tremors at their homes and places of work that were generated by <br /> whatever the blast hole pattern and size of charges were actually employed at the Dowe Flats <br /> Pit. These tremors were felt as far away as Apple Valley on the west side of Lyons, <br /> approximately 3 miles from the Cemex mine. <br /> Given our long term presence in the community, the Save Our St. Wain Valley(SOSVV) can <br /> state that this distance of seismic impact has not been previously recorded by the community. <br /> It remains unexplained by Cemex and is unacceptable to the surrounding residents who would <br /> not wish any negative consequences to wells. foundations and structures livestock chemical <br /> storage sites, etc. from blast induced seismic activity. <br /> The blast also raises the question as to what future directions are to be expected regarding <br /> Cemex, its mining, related manufacturing activities and the traffic, noise, dust and light <br /> pollution. <br /> It had been the community's understanding that the Cemex mining permit is set to expire on <br /> September 30, 2022 and that in a letter dated June 14, 2019, Mr. Case notified Uwe Lubjuhn, <br /> plant manager at Cemex that September 30, 2022 is the end of the 25-year mining permit and <br /> that all mining must cease on that date. <br /> It has also been the understanding of the community that Mr. Lubjuhn has responded to the <br /> County that it wishes to renew its mining permit for 25 more years. <br /> SOSW respectfully requests the Commissioners review this matter with staff, and let us know <br /> 1.)what the County's position and intentions are regarding Cemex's future activities in Dowe <br /> Flats, 2.)the status of the County's executed purchase agreement with Cemex. <br /> �erel <br /> L." <br /> Richard Cargill AL~� <br /> Board of Directors, SOSW <br />