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the distance between the blast and the nearest structure described in Rule 4.08.4(10) that lies outside <br />of the mine permit area. As stated in Rule 4.08.4(10) (c)(i), peak particle velocities that may occur <br />at these types of structures during blasting are deemed to be within State regulatory limits if blasting <br />is conducted in accordance with this mathematical formula. <br />Compliance with the State's ground vibration limits can thus be demonstrated with either ground <br />vibration recordings (using appropriate recording equipment appropriately, so long as peak particle <br />velocities do not exceed 1.0 ips), or with records and calculations demonstrating compliance with <br />the formula from Rule 4.08.4(10)(c)(i). <br />Rule 4.08.4(6)(a) describes the amount of airblast, expressed in decibels (dB), that is allowed to <br />occur at certain protected structures located beyond a mine's permit azea. These airblast limits vazy <br />not with the distance between those structures and the blasting site, but with the low frequency limit <br />of the airblast recording instrument: the lower the low frequency limit of the recording instrument, <br />the higher the maximum allowable airblast level at the protected structure. <br />Rule 4.08.4(6)(a) additionally requires operators like LCC to conduct periodic monitoring to ensure <br />compliance with State airblast standazds. Rule 4.08.4(6)(c) additionally requires airblast recording <br />instruments to have anupper-end frequency limit of at least 200 Hz. Rule 4.08.5(17) additionally <br />requires blast records to include annual certifications of recording equipment calibrations, or <br />records of calibration signals of recording equipment gain settings. <br />According to the information provided to DMG's office by Mr. Frank Smith on 5/29/02, the <br />microphone attached to the seismograph used to monitor the 5/16/02, 5/20/02, and 5/23/02 blasts <br />had a frequency range of 2 Hz to 200 Hz. The maximum airblast level expressed in decibels (dB) <br />allowed by Rule 4.08.4(6)(a) for those blasts at protected structures beyond the permit area would <br />thus have been 133 dB. My review of the blast logs for the blasts that are the subject of this review <br />found that the seismograph used to monitor the ground vibration and airblast levels from the blasts <br />was calibrated on 8/23/00. <br />I asked Mr. Smith on 6/4/02 if he had any calibration signals for the seismograph's gain settings. <br />Mr. Smith thought the traces labeled "Sensorcheck (R) Calibration" following the seismograph <br />record of 31ast #104-02 met this requirement. On 6/6/02, I faxed a copy of these traces to Mr. <br />Michael F. Rosenthal with the Office of Surface l~lining in Denver, to ask his opinion of whether <br />these traces were gain setting calibration signals (Mr. Rosenthal's background is in mining <br />engineering, and is a co-author of the 1987 OSM publication "Blasting Guidance Manual". Mr. <br />Rosenthal additionally assisted DMG eazlier this year with a previous Citizen's Request for <br />Inspection regazding ground vibration and airblast levels from the Lorencito mine). Mr. Rosenthal <br />informed me on 6/6/02 that the "Sensorclreck" calibrations are not gain setting calibration signals. <br />Blast #103-02 <br />The log for Blast #103-02 indicates that the blast was initiated at 4:38 pm on 5/16/02. The log <br />indicates that the distance between the blast and the Primero School was 6000 feet. I am not yet <br />awaze ofthe approximate location of Blast #103-02, so I cannot verify this 6000-foot value at this <br />time; I hope to obtain this information from Mr. Smith later this month. <br />