The inspection team probing the February 14 collapse of a portion of the parapet of the under-construction Metro-4 line on LBS Road in Mulund has recommended that the contractor replace the entire team handling the package for the Gandhi Nagar to Sonapur section.

The 6×4-foot boulder had fallen on a moving autorickshaw and Skoda car around 12.15 pm leading to death of one person and injuries to three persons.

The Mumbai Metropolitan Region Development Authority (MMRDA) had appointed the 9-member Special Intensive Safety Inspection Team led by the project’s chief engineer.

MMRDA said the panel found that the incident was “not attributable to any deficiencies in the structural design, construction materials or overall quality of construction works”. It added the incident occurred due to temporary supports being removed by a welder working with the contractor Reliance Infrastructure-Astaldi Joint Venture (RAJV) on a recently erected parapet segment.

A bench led by Bombay High Court Chief Justice Shree Chandrashekhar on March 4, while hearing a PIL by city-based advocate Ruju Thakker seeking a third party’s structural safety audit of all Metro lines, had sought a probe status report from the MMRDA. On the same day, the MMRDA had stated the incident took place due to the “negligence on the part of the consultant”. The PIL was not be heard on Wednesday due to time constraints.

The affidavit — submitted by Shivani Patil, Assistant Engineer Grade-I (Civil) of the MMRDA on Wednesday — in response stated, “There was procedural non-compliance by RAJV and insufficient site supervision by the General Consultant during construction activity.”

The Incident Report further stated that necessary “corrective actions and preventive measures shall be implemented to avoid recurrence of such incidents, which includes directing the General Consultant and RAJV to replace the entire team responsible for the CA10 (Gandhi Nagar to Sonapur package) contract”.

It referred to other recommendations to be undertaken by RAJV and the general consultant (a consortium of DB Engineering & Consulting GmbH, Louis Berger and Hill International) tasked to ensure compliance of safety procedures for the project.

The preventive measures include a strict adherence to the mandatory ‘Permit-to-Remove’ support system and a joint inspection by the site engineer, quality assurance/quality control engineer and safety officer before temporary supports are removed.

Other recommendations include implementing a segment tagging/colour coding system and the removal of temporary supports only after the stitch concrete achieves required strength.

The probe team also recommended deploying a dedicated supervisor to dismantle works, conduct mandatory toolbox talks prior to critical activities and ensure “no verbal-only instruction” is used for structural activities.

The probe, as per the MMRDA “identified several procedural and supervisory deficiencies by RAJV” including lack of authorisation prior to removal of support and “no joint inspection and no Request for Information (RFI) clearance or engineering verification confirming readiness of segments was done by RAJV before undertaking the task in question”.

The report further claimed the contractor executed the activity without following any defined checklist or sequence for dismantling.

“Furthermore, no tagging or marking system existed to distinguish structurally completed segments from incomplete ones, which directly contributed to inadvertent removal of supports by RAJV’s site team,” the affidavit stated.

It further added that RAJV’s site supervisor was responsible for giving “proper instructions to workmen regarding cutting supports of stitched parapet only, leaving temporary supports of unstitched parapets intact.”

“The welder who was carrying out the task of removing temporary supports may not have been able to identify/distinguish between stitched or unstitched parapet segments. Evidence from site photographs and incident scenario indicates that the cutting of the hook was inadvertently carried out by the welder and lack of supervision from RAJV’s supervisor as a result of which the parapet segment fell onto the live road,” the team had found.

An Interim Detail Incident Investigation Report of the incident prepared by the General Consultant concluded, “Incident primarily resulted from unsafe dismantling activity carried out by Contractor’s workers, without proper verification, supervision, permit clearance, or adequate public protection measures.” This was a preventable accident, it added.