Loading...
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 noan�cnaa�ru � 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 EQ �� 512 North Salisbury Street 1 1612 Mail Service Center I Raleigh, North Carolina 27699-1612 NORTH CAROLINA - oaPamnem of envmronmemai Quality /� 919.707.9200