PERMFILE104470

• Permit No: M2004067
• IBM Index Class Name: Permit File
• Doc Date: 9/21/2006
• Doc Name: Potential for Blasting Vibrations to damage Black Hawk Central City sewage treatment plant
• From: DRMS
• To: AGO
• Media Type: D
• Archive: No

STATE OF COLORADO
t>~>~Y
Oepa~ucent d Naoeral Reeoueoes
1x77 sheeenan 5t, Room 215
DaeneG Colorado 80203
Plenee: [phone]
FAX:[phone]
EO
DO
OP
lLS
GY
DATE: November 21, 2005 sn °w"
roMSeeor
TO: Tom Schreiner o7~am,
awld w. raeea~y
FROM: Allen Sorenson ~'b" D1neor
Nannai IOewwc. reue/ee
RE: Review ojBlast Vibration Analysis Repoli Prepared Z1' Leonard Rice Engineers, Ina,
Clear Creek DiaMct Water Providers, LLC, MMRR Quarry, File Na M-2004-067
The Division of Minerals and Geology engineering staff (DMG) have reviewed the November 10, 2005
report, prepared by Leonard Rice Engineers, titled "Blast Vibration Analysis of Proposed MMRR Quarry
on the Black Hawk/Central City Wastewater Treatrnent Plant and Silver Dollar Metropolitan District
Facilities," (Rice Report). Phis includes the review of the final version of Appendix B to the above
captioned report received at ttte 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: .
1. 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 struetures will exceed commonly acceptable Levels, as
described in the blasting literature, atnearby 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 Chary' 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 aceordance with the Blasting bevel Chart). WiW 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 aceeptable"
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 modem 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 Faciliuea 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.
osl~d
Mlrred land Reedamation
oslae d
Mive and Iepc7We Mines
calorado
CeoloBtea{ Survey