REP39226

• Permit No: M1993041
• IBM Index Class Name: Report
• Doc Date: 11/9/1993
• Doc Name: TECHNICAL APPENDIX MINING IMPACTS ON MONTGOMERY SCHOOL DOWE FLATS MINING AND RECLAMATION PROJECT
• Media Type: D
• Archive: No

1
' ~S ~
~~i
t

1

1
1
1

1

Southwestern Portland Cement
Mining Impacts on Montgomery School
SHB AGRA Project E93-7038
Page 6
delay of 1600 pounds and a typical charge weight per delay of 400 pounds. The distance was
measured from the existing "C" pit at the Lyons Quatry to the property.
In summary, this analysis indicates the existing Lyons mining operation is potentially subjecting
the Montgomery School Building to peak ground velocities on the order of 0.18 in/sec. The
maximum explosive weight of 1600 pounds at the Dowe Flats site could result in peak ground
vibrations that exceed the 0.25 inlsec compliance level recommended for the Montgomery
School site during the first 10 years of mining. The typical blast using 400 pounds of explosive
per delay will result in maximum peak vibrations that are essentially at the.compliance limits for
the first two yeazs of mine development and decrease with time. Accordingly, controls will need
to be incorporated in blasting during initial mine development to achieve compliance with the
recommended ground vibration limits. The modified blasting operation as has been conducted
at the Lyons Quarry over the last 8 to 10 months demonstrates this control can be implemented
without excessively restricting mine production. After approximately 5 years, ground vibrations
at the Montgomery School will be at or below levels associated with the existing Lyons Quarry,
as mining at Dowe Flats moves from south to north.
A frequently raised concern in ground vibration analysis is the potential for several sources of
ground vibration such as highway traffic and blasting to cause an additive effect resulting in a
higher ground vibration than induced by any given source. This can potentially be an issue with
steady state vibration sources such as machines that induce vibrations that are at a near constant
frequency. With transient ground vibrations such as result from blasting, truck traffic or trains;
both the frequency and amplitude of the induced ground vibration are essentially continuously
changing. Further, the duration of the vibration is very short, ranging from hundredths of a
second with blasting vibrations to a few seconds with vehicle-induced vibration. As such, it is
improbable that two or more ground vibration wave sets would occur in such a manner as to
have an additive effect. This is demonstrated by the vibration monitoring performed of the truck
traffic into and out of the Lyons Cement Plant as reported May 24, 1993 (SFfB AGRA, 1993a).
Of the 19 monitoring tests, four included multiple vehicles passing the monitoring station. These
tests resulted in vibrations essentially identical to single vehicles, with no indication of
cumulative effects.
6.0 MONITORING AND CONSERVATION PROGRAM
For the life of the mining operation, a monitoring and conservation program is proposed to be
implemented. The objective of the program is to confirm that the compliance criteria is being
met and that the compliance level is providing for adequate protection of the Montgomery School
Building.
The program will start with apre-mine construction and pre-blast survey and structure
assessment of the school to establish a baseline condition record, providing the owner allows
access. During the baseline survey, an extensive photographic record of the building will be
made. Photo point datums will be permanently established (i.e. rebaz sunk in concrete in the
' L^ A G R A
Earth & Environments/Group