Laserfiche WebLink
Memo to Tom Schreiner 4 September 9, 2005 <br />Review of Geotechnical Exhibit File No. M-2004-067 <br />b. Exact location of instrument and the date, time and its distance from the blast; <br />c. Name of the person and firm taking the reading; <br />d. Name of the person and firm analyzing the seismographic record; <br />e. The vibration level recorded. <br />In addition, the DMG requires apre-blast survey of potentially affected structures. Pre-blast surveys must be <br />conducted at all stmctures located within one-half mile of the proposed permit boundary unless persons in <br />ownership or control deny access to the structures. Written requests to conduct pre-blast surveys must be sent to <br />owners of all structures a minimum of 30-days prior to initiation of blasting. The Applicant must provide a plan <br />for DMG review and approval for the conduct of the survey. There is ample information on the conduct ofpre- <br />blast surveys contained in the blasting literature. <br />Finally, a plan must be submitted for DMG review and approval stating enforceable management practices that <br />will be employed to prevent flyrock and minimize dust caused by blasting. The main control that can be applied <br />to the blast design is to ensure proper burden and stemming together with loading explosives to place energy <br />release at the points where it will most efficiently break rock. In blasting locations where it is physically <br />impossible to ensure proper burden and stemming relationships, blasting mats or application of thick dirt cover <br />must be used. Watering of blast locations maybe necessary to control dust, particularly when dirt cover for <br />flyrock control is employed. Also, the Operator must commit to curtailment of blasting when weather <br />conditions are windy and/or dry such that transmission of dust beyond the permit boundaries would be <br />increased. <br />DMG has considered the concern expressed by the Black Hawk/Central City Sanitation District that quarry <br />blasting could trigger movement on the Black Hawk Fault. DMG concurs with the Applicant that blasting will <br />have no impact on the fault. The ground vibration limitations imposed by compliance with any of the above <br />listed four compliance options are designed to prevent damage as slight as the aggravation of existing minor <br />cracks in plaster. As such, these controls are more than adequate to prevent activation of a geologic fault, and <br />more than adequate to ensure that no damage will occur to the industrial concrete structures at the Black <br />Hawk/Central City Sanitation District wastewater treatment plant, or to any of the other structures within the <br />zone of influence of the quarry related blasting vibration. <br />Given the pending decision date for the MMRR Quarry, DMG will need the Applicant's responses to this memo <br />by September 14, 2005. If the Applicant has questions about this memo, I can be reached at 303-263-7886. <br />attachment(s) <br />cc: Carl Mount, DMG (via email and w/o attachments) <br />Harry Posey, DMG (via email and w/o attachments) <br />Bruce Humphries, DMG (via email and w/o attachments) <br />c:~Documrnts and SettingsWCSVNy DocumenlsgvlMRRsdequacy of the geotech stability exhibit.doc <br />