PERMFILE104894

• Permit No: M2004067
• IBM Index Class Name: Permit File
• Doc Date: 11/21/2005
• Doc Name: Review of Blast Vibration Analysis Report by Leonard Rice Engs Inc
• From: Allen Sorenson
• To: Tom Schreiner
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
DATE: November 21, 2005
TO: Tom Schreiner
FROM: Allen Sorenson ~~
COLORADO
DIVISION O F
MIN SRALS
GEOLOGY
AECLANATION•MI NING
EAf ETY•SOFNCE
Bill Owens
Govema
Russell George
Executive Director
Ronald W. Cattany
Division Direc7or
Natural Resauroe Trustee
RE: Review of Blast Vibration Analysis Report Prepared by Leonard Rice Engineers, Inc.,
Clear Creek District Water Providers, LLC, MMRR Quarry, File No. M-2004-067
The Division of Minerals and Geology engineering staff (DMG) have reviewed the November 10, 2005
report, prepazed by Leonard Rice Engineers, titled "Blast Vibration Analysis of Proposed MMRR Quarry
on the Black Hawk/Central City Wastewater Treatment Plant and Silver Dollar Metropolitan District
Facilities," {Rice Report). This includes the review of the final version of Appendix B to the above
captioned report received at the DMG on November 16, 2005. The Rice Report describes two concerns
with the blasting plan included in the MMRR Quarry application relative to the nearby valuable
structures:
That receptors resident in nearby structures are susceptible to damage from vibration levels lower
than those commonly acceptable in the extensive preponderance of blasting vibration literature
and experience.
2. That the vibration levels at nearby structures will exceed commonly acceptable levels, as
described in the blasting literature, at nearby so-called sensitive receptors.
The MMRR Quarry Applicant has committed to blasting during development and operation of the quarry
in accordance with the well-known "Blasting Level Chart" compliance option. The Applicant has further
committed to detonation of initial blasts in accordance with the highly conservative "Scaled Distance
Equation." (Results of vibration measurements taken during initial blasting will establish criteria for
subsequent blasting to be conducted in accordance with the Blasting bevel Chart). With these
commitments in place, there is no possibility, absent anon-compliant action, that vibration levels at
nearby receptors will exceed commonly acceptable levels. Therefore, the DMG analysis need only
consider the Rice Report's contention that nearby receptors are susceptible to damage by vibration levels
below those that are commonly acceptable. As background, these so-called "commonly acceptable"
blasting vibration levels have been codified in regulations adopted by the United States Office of Surface
Mining, the Colorado Department of Labor, as well as countless other agencies worldwide. The DMG
Minerals Program has not adopted dogmatic adherence to "commonly acceptable" blasting vibration
levels because modern blasting practices and blast monitoring methods frequently allow vibrations levels
well above those that are "commonly acceptable" while still assuring that nearby sensitive structures will
not be damaged.
The Rice Report describes receptors in the Black Hawk/Central City Wastewater Treatment Plant and
Silver Dollar Metropolitan District Facilities that the report states may be damaged by blasting vibration
levels below those proposed by the Applicant, which levels have been found acceptable by the DMG.
Office of Office of Colorado
Mined land Reclamation Active and Inactive Mines Geological Survey