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<br />iii iiiiiiiiiiiii iii <br />_I_ 999 <br />IS '' SHB AGRA, INC. <br />1 ' B L Engineering&Environmenla/Services <br />t -' <br />September 17, 1993 <br />Mr. John Lohr <br />Southwest Portland Cement Company <br />P.O. Box 529 <br />Lyons, Colorado 80540 <br />Regarding: Blasting Related Ground Vibration <br />Dowe Flats Project <br />Lyons, Colorado <br />Dear Mr. Lohr: <br />165 South Union Blvd. <br />Suite 516 <br />Lakewood, Colorado <br />U.S.A. 80228 <br />Phone: 303-76&8432 <br />Fax: 303-989-5525 <br />SHB AGRA Project E93-7038 <br />As requested, we have evaluated the ground vibrations due to blasting at various properties <br />around the proposed Dowe Flats Project to estimate the change in peak ground velocity and the <br />corresponding potential for damage to offsite structures, as the mining progresses from north to <br />south. Peak ground vibrations were estimated using the relationship between peak ground <br />velocity, distance from the blast and explosive weight developed from monitoring of blasting at <br />the existing Lyons Quarry (SHB AGRA, 1993). Properties considered in this evaluation are <br />indicated on the attached Figure 1. <br />Estimation of ground vibration was done on an annual basis considering the nearest location that <br />blasting will occur in a given year. As noted in the Blast Vibration Analysis Report (SHB <br />AGRA, 1993), blasting at the Lyons Quarry used a broad range of explosive charge weights per <br />delay depending on the nature of the blast. Figure 2 presents a summary of the frequency that <br />given explosive charges were used over the period of the blast vibration analysis. As shown in <br />Figure 2, the range of charge weights per delay that are used range from less than 100 pounds <br />to 1600 pounds. Over 50 per cent of the shots, however, used charge weights per delay in the <br />range of 200 to 400 pounds. Ground vibration estimates were therefore made for a typical blast <br />with a charge weight per delay of 400 pounds and the upper limit blast of 1600 pounds of <br />explosive. <br />The estimated distances from the various properties to the nearest portion of the mine at each <br />year of mine development and the estimated ground vibration under the typical and maximum <br />blasts are presented in Table 1. Figures 3 through 8 present plots of the estimated ground <br />vibrations at each property with time. Also presented on Figures 3 through 8 are the Office of <br />Surface Mining Reclamation and Enforcement (OSMRE) regulations for control of blasting at <br />L^ A G R A <br />Eerth & Environments/Group <br />