20211022_Blasting_Response_letter_01-10-allen

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ROY COOPER
Governor ? i' - r
ELIZABETH S.BISER
Secretary
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BRIAN WRENN NORTH CAROLINA
Director Environmental Quality
October 22, 2021
Mr. Tim Allen
8152 Sylvan Road
Liberty,NC 27298
RE: Blasting Complaint
Alamance Aggregates and Construction Materials Quarry
Mining Permit No. 01-10
Alamance County
Cape Fear River Basin
Dear Mr. Allen:
Our office has completed its review of Alamance Aggregates, LLC's blasting information, including blast reports
and seismograph recordings, related to the August 26, 2021, through October 19, 2021, blasts conducted at the
Alamance Aggregates and Construction Materials Quarry. It was found that Alamance Aggregates, LLC was in
compliance with the blasting requirements of its mining permit during the period in question.
All peak particle velocities, a measurement of ground vibration with units in inches per second (ips), were well
below the maximum allowable limits specified in Alamance Aggregates,LLC's mining permit. More specifically,
all recorded values were at or below 0.135 ips at the closest offsite occupied structure (the location where
compliance with the permit limits is determined). According to extensive research by the U.S. Bureau of Mines
and others,particle velocities below 0.5 ips effectively eliminate the possibility of any structural damage.
All airblast readings,a measurement of the atmospheric pressure wave(overpressure)with units in psi or dBL,were
also below the maximum allowable limits specified in the mining permit and well below the U. S.Bureau of Mines'
recognized level of 164 dBL for prevention of glass breakage. More specifically, all recorded values were at or
below 117.1 dBL at the closest offsite occupied structure (the location where compliance with the permit limits is
determined). A key point worth noting is that glass breakage occurs at much lower levels of overpressure than
structural damage, such as cracking plaster.
Thank you for your interest and patience in this matter. Hopefully, I have answered your concerns adequately. If
you should have any additional questions or concerns,please contact me at(919) 707-9220.
Sincerely,
A-t-t-
Adam Parr, PE
Assistant State Mining Engineer
cc: Ms. Tamera Eplin,PE
D E Q�� North Carolina Department of Environmental Quality I Division of Energy.Mineral and Land Resources
512 North Salisbury Street 1 1612 Mail Service Center I Raleigh,North Carolina 27699-1612
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919.707.9200