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STATE Or COI ORADO Hi1:HnHl~ n, L4MM, nnvcmnr III IIIIIIIIIII I <br />DEPART MENi OF NATURAL RESOURCES 999 <br />D. Monte Pascoe, Execut rve Duector <br />1~11NEU L,ANU RECLAI~IA'TION <br />423 Centennial Build mg, 1313 Sherman Street <br />Denver, Colorado 80203 Tel.(30~) 839-3567 <br />David C. Shelton <br />Director <br />TO: Pete Evans <br />FROM: Jim Pendleton <br />RE: GEC Mineral Inc 'Detailed BZasting Plan" <br />Pursuant to your request I have reviewed GEC Mineral's "Detailed Blasting <br />Plan", in order to determine whether or not it conforms with the requirements <br />of Rule 4.08 of the permanent Colorado program regulations. It has several <br />deficiencies which must be corrected. <br />1. The report of blast monitoring performed by VMe Nitro-Consult, Inc., is <br />inconclusive. The consultant states within that report that allowable <br />weights of ANFO with 8 mili-second delays can be safely increased <br />above the 25 lb. Load used during the test blast which was monitored <br />on January 28, Z98Z. However, the report also states that the data <br />gathered was insufficient to yield a reliable regression analysis. <br />The consultant cannot project with confidence what weight load would <br />result in less than the regulatory limit of 1" per second peak ground <br />acceleration at the critical structures on the neighboring Dorchester <br />mine. The operator's consultant must perform the necessary empirical <br />observations before permission could be granted to utilize explosive <br />loads exceeding the limits of Rule 4.08.4(10)(b). <br />2. The "velocity curve" and "charge/delay vs. distance" figures included <br />within VME Nitro-Consultant's last monitoring report were insufficiently <br />labeled. I cannot discern for what Load and delay the first figure <br />was projected or for what peak particle velocity the second figure is <br />projected. The consultant should remedy these defects by re-drafting <br />the figures. <br />3. I assume that the operator will acknowledge conformance with the <br />various requirements of Rule 4.08, such as blast reporting, blast <br />schedule publication, etc. <br />Until these deficiencies are remedied the operator will not be in conformance <br />with Rule 4.08, and I cannot recommend your approval of the plan. <br />1 <br />/k <br />February 10, 1981 <br />