Additional safety measures will be implemented, including using an independent safety consultant, when blasting resumes Friday at the site of the Second Avenue Subway Station, the Metropolitan Transportation Authority said.
The MTA Thursday announced results of an investigation of an Aug. 21 blasting incident that sent boulder-sized debris flying into Upper East Side streets, shattering windows and frightening residents and merchants.
The investigation concluded several factors, including incorrectly drilled blast holes and an improperly timed blast sequence, contributed to the incident.
"We have completed our review of the incident and have implemented a number of corrective actions," said Michael Horodniceanu, president of MTA Capital Construction. "Blasting operations will be subject to additional management scrutiny and enhanced safety procedures to ensure that the community and workers are kept safe."
Improvements to safety include superintendent sign-off on a pre-blast checklist; a second licensed blaster to verify that each blast has been prepared in accordance with the approved blast plans; and a double layer of protective blast mats that will be used when blasting in shafts.
A review of the steel decking system has been completed and found to be able to withstand uplift pressure and that all personnel responsible for inspecting and monitoring blasting have been retrained, the MTA said.
The investigation determined that several factors contributed to the incident:
Failure of the contractor to adhere to the approved blast plan
Improper blast timing sequence causing excessive blast force
Orientation of the drilled holes, which were angled rather than vertical
Use of 10-12 foot long blast holes, which may not have been drilled properly
Sloped condition of the rock and inadequate rock cover
Failure of the decking system to contain the debris
The incident review is detailed in the full report, which is available online at mta.info/capconstr/sas/documents/Report%20SAS%20Aug%2021%20Incident_FINAL.pdf