Trees hurtling to death as NMC uses concrete base beneath paver blocks

Nagpur: Seven years after the Nagpur bench of Bombay High Court took serious note of "cementing and tarring around trees on city roads", the trees right in front of the HC building in Civil Lines are choking due to rampant concretization of roads that is taking place all over the city.

Defeating the very purpose of going in for paver blocks, green activists alleged that the Nagpur Municipal Corporation (NMC) is laying concrete base below the tiles, thus obstructing rainwater percolation.

Based on inputs received from activists, TOI visited Civil Lines where the work of concreting the West High Court (WHC) Road is in progress. At both sides of the road, a thick layer of around four-inch concrete was clearly visible under the paver blocks.

Stating that use of concrete at roadside was unscientific, experts said that the it will restrict natural seepage of water. "This will not only decline the groundwater recharge but also lead to slow death of trees," said green activist Shrikant Deshpande.

Paver blocks are used to ensure water percolates to tree roots and recharges groundwater.

As per the guidelines of Indian Roads Congress (IRC), the sub-base layers should be of "granual material" to ensure that proper disposal arrangement for water is made. They add that in case of pavements with light traffic like pedestrian sidewalks, footpaths, cycle tracks and parking area, the blocks should be laid over a sand bedding.

'The base course can be water-bound macadam (WBM), wet mix macadam (WMM), crushed stone or soil-cement', the rules state.

In February this year when road concretization work was in full swing, NMC's then chief engineer Ulhas Debadwar had issued a circular, directing that concrete base should not be used while paving tiles. "It can be laid below the tiles only in exceptional circumstances like in case of weak sub-grade soils (soil that lies below ground level), low level of groundwater table and at traffic junctions. In all other places, granular sub-base and WBM should be used," it stated.

The circular also mandated providing "breathing space" for trees. "The contractor should leave a space of one square meter space around the tree base and the garden department should put fertilizer-mixed earth into it," Debadwar had directed.

He had also prepared a design for carrying out rain water harvesting during concretization work. However, none of the directions seems to be followed.

Current chief engineer of NMC Vijay Banginwar said that using concrete becomes necessary at places where traffic movement is expected. "If cement is not used in the base, the tiles will get disturbed. However, to ensure water percolation, we are using lean (thin) cement," he said, adding that NMC will avoid concrete use wherever possible.

Activists said that the current use of concrete was unscientific. "Even at places where no traffic is expected like the area close to and between trees, the civic body is mindlessly using concrete," said Deshpande.

Founder of Green Vigil Kaustav Chatterjee said that recharging pits at both sides of the road are a must. "The speed of percolation of water is much slower than the rate in which water will flow through drains. Now with concretization of roads, the scope of water percolation has reduced further and thus recharge pits are needed," he added.

A senior civic official, on the condition of anonymity, said that a survey should have been done to find out areas where concrete use was not needed. "NMC needs to take measures for water harvesting. Laying concrete beneath paver blocks will result in drastic depletion of groundwater," he said.