MUMBAI: After two people died, one of them a child, when trees collapsed on them in the last three days, the civic administration has ordered a week-long audit of trees across Mumbai to identify those at risk and to remove concrete choking their roots.BMC orders city-wide audit of trees amid concretisation workThe directive follows numerous incidents of trees collapsing even as the monsoon only begins to get underway. The likely cause of these frequent tree collapses – now an annual occurrence – is the road concretisation drive entombing their roots, cutting off access to nourishment, and weakening them.Municipal commissioner Ashwini Bhide has also told civic engineers and contractors to protect trees while carrying out future infrastructure work.The directions come as the BMC undertakes the concretisation of nearly 700km of roads. Footpaths and stormwater drains too are being rebuilt, putting at risk thousands of trees that stand in their path.A circular issued in Friday has acknowledged that excavating close to tree trunks or concreting around their bases can weaken root systems, increasing the risk of trees toppling during heavy rain or strong winds.It reminds road engineers that all excavation near trees must maintain a minimum distance of 1 metre around the base of the trunk. Excavation within this zone should be carried out manually and not with earthmovers or excavators.The circular also states that vertical clearance of 0.3m to 1m must be maintained around every tree trunk while constructing roads, footpaths or stormwater drains – 1m for smaller trees and a 0.3-m gap for larger trunks.The area around the trunk must also remain free of concrete and construction debris, and instead be filled with black soil. Tree grates must be installed wherever necessary.Significantly, the BMC has ordered engineers to inspect even roads that have been concretised. They have been told to inspect every road and footpath under their jurisdiction within seven days and record the number of trees.Where concrete has been laid right up to the trunks, it must be removed, creating a clear soil basin 0.3 to 1 metre deep around the tree, depending on the trunk size.Road engineers have been told to submit daily progress reports, which will eventually be filed with the municipal commissioner.The circular also directs engineers to alert the local ward’s garden department if they identify a tree in danger of tilting or falling, so that action can be taken without delay.