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Southwestern Portland Cement <br />Mining Impacts on Montgomery School <br />' ~~~ SHB AGRA Project E93-7038 <br />~. B' Page 1 <br />SUMMARY <br />t SHB AGRA and Western Historical Studies (WHS) have performed an analysis of potential <br />impacts at Montgomery School as a result of development of the Dowe Flats mine, as directed <br />' by Colorado State Historical Preservation Office and the Boulder County Parks and Open Space <br />Department and as part of following the Section 106 of the National Historic Preservation Act <br />model for cultural resources management. This evaluation included: <br />t 1) baseline documentation of existing ground vibrations at the site <br />' 2) literature review to identify applicable ground vibration standazds <br />3) development of recommended compliance standards <br />4) projection of ground vibrations from the Dowe Flats quarry operations <br />' S) development of a monitoring program for the Montgomery School. <br />Based on this analysis, a ground vibration compliance value of 0.25 inches/second is proposed <br />' for the Montgomery School. Monitoring and conservation actions will be performed, with owner <br />approval, during mining operations to confirm compliance with the vibration limits and to <br />document any changes in building conditions. <br />' 1.0 INTRODUCTION <br />' Southdown, Inc., a corporation doing business in the State of Colorado as Southwestern PoNand <br />Cement Company, is planning to open a new limestone quarry in the Dowe Flats azea, located <br />north of Colorado Highway 66 and west of Boulder County Road 47, in Boulder County, <br />' Colorado. Mining plans, currently under development, include open pit mining with the use of <br />explosives to fracture and loosen the limestone for haulage to the nearby cement plant, situated <br />south of the highway. Mining plans call for blasting to be conducted three to four times per <br />' week, between the hours of 10 am and 2 pm. <br />Offsite effects of the blasting include ground vibrations and an air pressure pulse referred to as <br />' air overpressure. Both effects are capable of inducing damage in buildings, however the ground <br />vibrations have the greatest potential for inducing structural distress in buildings. Excessive <br />levels of air overpressure would result primarily in the potential for glass breakage as opposed <br />t to damage to the structural integrity of the building. <br />Montgomery School is located neaz the northwest corner of Highway 66 and County Road 47. <br />The school building, which is listed on the National Register of Historic Places, is currently <br />occupied as asingle-family residence. The school building is significant for its role in the <br />development of the local community and as an example of the type of stone construction that was <br />populaz in the Lyons azea during the late nineteenth and early twentieth centuries (built in 1917). <br />As an azchitectural resource (example of local stone building techniques) its value as a National <br />Register property is clearly tied to it's architectural presence and impacts to the building's fabric <br />AG RA <br />' Earth & Em+ironmentei Group <br />