PERMFILE57156

• Permit No: M2004067
• IBM Index Class Name: Permit File
• Doc Date: 9/9/2005
• Doc Name: Review of the Geotechnical Stability Exhibit
• From: Allen Sorenson
• To: Tom Schreiner
• Media Type: D
• Archive: No

Memo to Tom Schreiner 3 September 9, 2005
Review of Geotechnical Exhibit File No. M-2004-067
3. Modified Scaled Distance
Both the Maximum PPV (option no. 1 described above) and this Modified Scaled Distance option rely on site-
specific seismograph measurements, but the Modified Scaled Distance option translates the measurements into a
statistically predictive scaled distance, with a confidence level of 95 percent. This translation allows for shots to
be fired without regular seismograph measurements; annual review and renewal of the Modified Scaled Distance
is required by DMG. Seismograph data collection of PPV must be conducted prior to DMG's initial
authorization of Modified Scaled Distance and at least annually thereafter. At least 30 pairs of good quality PPV
and scaled distance data are required for authorization. Data collection for initial authorization must be done
using blasts that conform to the regular Scaled Distance Equation. The specifics for implementing a Modified
Scaled Distance compliance method are readily available in the blasting literature.
4. Blasting Level Chart
For this compliance option, every shot must be monitored using a seismograph with frequency responsiveness.
If the measured PPVs are below the frequency related maximum PPV line on the Blasting Level Chart (copy
attached), then the blast is in compliance. If the Applicant selects this option, they must specify seismograph
locations for DMG review and approval, and must commit to using the Scaled Distance Formula for initial
blasting. Once initial results are analyzed, charge weight per delay can be increased sequentially until it is
determined what maximum charge weights can be used without exceeding the maximum allowable PPVs.
In order to gain DMG approval of the permit application relative to blasting vibration compliance, the Applicant
must select one of the above listed compliance options and provide a detailed description for DMG review and
approval of mechanisms through which the selected option will be implemented. DMG further requires a record
of each blast, including seismograph reports, that must be retained for at least 3 years and be available for
inspection by the DMG on demand. The record shall contain the following data:
1. Location, date, and time of blast;
2. Name, signature, and license number ofblaster-in-charge;
3. Identification, direction and distance, in feet, from the nearest blast hole to the nearest dwelling, school,
church, or community or institutional building either:
a. Not located in the permit area; or
b. Not owned nor leased by the person who conducts the mining operations.
4. Weather conditions, including temperature, wind direction, and approximate velocity;
5. Type of material blasted;
6. Sketches of the blast pattern including number of holes, burden, spacing, and delay pattern.
7. Sketches shall also show decking, if holes are decked to achieve different delay times within a hole;
8. Diameter and depth of holes;
9. Types of explosives used;
10. Total weight of explosives used per hole and maximum weight of explosives used per 8-millisecond
period;
11. Initiation system;
12. Type and length of stemming;
13. Mats or other protections used;
14. Type of delay detonator and delay periods used;
15. Number of persons in the blasting crew; and
16. Seismographic records, where required, including:
a. Type of instrument, sensitivity, and the calibration signal of the gain setting or certification of
annual calibration;