HomeMy WebLinkAbout20210312_Blasting Response letter 53-01ROY COOPER
Governor
DIONNE DELLI-GATTI
Secretary
BRIAN WRENN
Director
Mr. Michael McGill
Martin Marietta Materials, Inc.
2710 Wycliff Road
Raleigh, NC 27607
RE: Blasting Complaint
Lemon Springs Quarry
Mining Permit No. 53-01
Lee County
Cape Fear River Basin
Dear Mr. McGill:
NORTH CAROLINA
Environmental Quality
March 12, 2021
The review has been completed on the shot records you previously submitted for the January 29, 2021 through
February 15, 2021 blasts at the Lemon Springs Quarry. Your company has been found to be in compliance with
the blasting conditions outlined in Mining Permit No. 53-01.
Thank you for your continued cooperation. If you should have any questions on the above, please contact me at
(919) 707-9220.
Sincerely,
Adam Parr
Assistant State Mining Engineer
cc: Mr. Bill Denton, 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
ROY COOPER
Governor
DIONNE DELLI-GATTI
Secretary
BRIAN WRENN
Director
Ms. Marilyn Butler
2889 Minter School Road
Sanford, NC 27332
RE: Blasting Complaint
Lemon Springs Quarry
Mining Permit No. 53-01
Lee County
Cape Fear River Basin
Dear Ms. Butler:
�Q/AM VIO��
NORTH CAROLINA
Environmental Quality
March 12, 2021
Our office has completed its review of Martin Marietta Materials, Inc.'s blasting information, including blast reports
and seismograph recordings, related to the January 29, 2021 through February 15, 2021 blasts conducted at the
Lemon Springs Quarry. It was found that Martin Marietta Materials, Inc. 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, Inc.'s mining permit. More
specifically, all recorded values were at or below 0.145 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. 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
Assistant State Mining Engineer
cc: Mr. Bill Denton, PE
D North Carolina Department of Environmental Quality I Division of Energy, Mineral and Land Resources
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512 North Salisbury Street 1 1612 Mail Service Center I Raleigh, North Carolina 27699-1612
NORTH CAROLINA -
oaPamnem of envmronmemai Quality /� 919.707.9200