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

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
pepartment of Natural Resources
1313 Sherman St., Room 215
penver, Colorado 80203
Phone: [phone]
FAX: [phone]
DATE: September 9, 2005
TO: Tom Schreiner ~~~
FROM: Allen Sorenson
. i
COLORADO
D I V I S I O N O F
MINERALS
GEOLOGY
PECLAMATION•NINING
SAf ETY4CIENCE
Bill Owens
Governor
Russell George
Eze[utive DIreLTOr
Ronald W. Cottony
Division Direttor
Natural Resource Trustee
RE: Review of the Geotechnical Stability Exhibit, Clear Creek District Wat r Providers, LLC,
MMRR Quarry Permit Application, File No. M-2004-067 (~,..pg ; ~itl.I,,,w~
The Division of Minerals and Geology (DMG) engineering staff have completed a review of portions of the
Applicant's adequacy responses relevant to the Geotechnical Stability Exhibit. In particular, the August 2005
report prepared by Lyman Henn, Inc. to support the application was the focus of this review.
The DMG agrees with the Applicant's conclusion that the mine development and quarry operations will have no
impact on the bulk stability of any offsite manmade structures. This conclusion is based on the geometry of the
quarry relative to the offsite structures; all relevant structures are lower in elevation than the eventual floor of the
quarry, which eliminates the potential for the quarry to undercut the structures and eliminates the potential for a
slope failure caused by quarry operations to damage the stmctures.
The Lyman Henn report provides a plan for the protection of offsite manmade structures from possible blast
vibration damage. The plan proposes limiting the weight of explosives to be detonated during delay periods of
minimum 8 milliseconds (ms.) between explosions. The basis for determination of maximum allowable charge
weights per delay is the equation:

Where: V=Maximum peak particle velocity (inches per second)
K=Ground transmissivity constant, assumed at 160 in absence of site specific seismic data
R=Distance to item of interest (feet)
W=Maximum pounds of explosive per delay period
This formula is an often quoted and referenced general use velocity attenuation relationship, and it is
conservative. However, it is not nearly as conservative as the Scaled Distance Equation, which has been long
accepted and employed by DMG for the development of blasting vibration compliance plans. Therefore, the
general use formula is not acceptable to DMG as a compliance option. As justification, DMG notes that the
Office of Surface Mining "Blasting Guidance Manual," March, 1987 at page 86 states that the formula should
not be used if"local conditions are anything more than non-critical." Acceptable compliance options are as
follows:
1. Maximum Peak Particle Velocity(PPV)
A seismograph record must be provided for each blast, and each shot must meet the following criteria:
(a) From 0-300 feet distance from blast to structure, maximum PPV is 1.25 inches per second (ips)
(b) From 301-5000 feet distance from blast to structure, maximum PPV is 1.00 ips
Office of Office of Colorado
Mined Land Rxlamation Active and Inactive Mines Geological Survey