20230214_Blasting Response letter 01-08_BJ

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ROY COOPER
Governor ? i' - r
ELIZABETH S.BISER
Secretary
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DOUGLAS R.ANSEL NORTH CAROLINA
Interim Director Environmental Quality
February 14, 2023
Brian Jordan
1154 Stonewall Springs Rd.
Burlington,NC 27217
RE: Blasting Complaint
East Alamance Quarry
Mining Permit No. 01-08
Alamance County
Cape Fear River Basin
Dear Mr. Jordan:
Our office has completed its review of Martin Marietta Materials's blasting information,including blast reports and
seismograph recordings, related to the December 28, 2022, and January 27, 2023 blasts conducted at the East
Alamance Quarry. It was found that Martin Marietta Materials 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 Martin Marietta Materials's mining permit. More specifically,
all recorded values were at or below 0.12 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 pounds per
square inch(psi)or decibel(dB),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 dB for prevention of glass breakage. More
specifically,all recorded values were at or below 116 dB at the closest offsite occupied structure 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,
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
NORM CAROLINA -
oePanmamotenmmnmamaiouaiN / 919.707.9200