Mumbai Monorail depot may not withstand an earthquake

Mumbai’s Monorail is “not conforming to earthquake-resistant designs” as initially mentioned in the contract document, says the CAG.

What is shocking is the compromise made for a structure that houses the operations and control centre, workshop, stabling yard, administrative building, etc.

“The monorail contract document specified Indian Standards 1893 as the criteria for earthquake resistant design of civil structures. As per this standard, all important services and community buildings and those required for emergency preparedness are to be designed with an Importance Factor (IF) of 1.5,” notes the CAG report.

But the project management consultant realised that the construction of the depot was being carried out at a lower grade of 1 IF. By the time time that was brought to notice for correction by the consultant, 70% of the piles for the depot building was ready.

“LTSE subsequently corrected the IF from 1.0 to 1.5 by simultaneous reduction of various loads in the depot building by revising the designs,” reads the CAG report. Changes were made to thickness of internal walls, only mass of empty train was considered in the seismic analysis instead of a fully loaded train, etc.

MMRDA maintained that the design of the depot building is for seismic zone 4, which is a high risk zone and Mumbai falls under zone 3 (a lower grade), thus acceptable, but CAG rejected the explanation.

Similarly, beam joints of the guideway too is not as per standard and due to that it may reduce the ductility required for seismic zone 4 areas.