Delhi: Tunnel proposed below Ridge, expert panel calls for seismic study

As per the minutes, “the alignment passes through southern ridge with a length of about 2 km”.

The proposal, however, states that “no trees are proposed to be cut within the boundary of Southern/ Morphological Ridge. About 1,286 trees have been counted within the proposed RoW [right of way] at the approaches of proposed tunnel and existing Nelson Mandela Marg which are out of Ridge boundary. Most of the trees falling along the alignment are part of agroforestry/ avenue plantation and along the existing road.”

The EAC recommended the proposal for granting of terms of reference along with specific conditions. These include one that states that “a comprehensive assessment of impact of seismicity on tunnel stability needs to be studied by a reputed institute and should be incorporated in the EIA [environment impact assessment] report. Another condition was that “a comprehensive hydrological and hydrogeological investigation shall be conducted by a reputed institute for the site…”

The granting of ToR is part of the process for obtaining environment clearance. The ToR provides the project proponent, in this case, the NHAI, with the issues to be considered while doing a detailed environment impact assessment study.

The documents submitted for environment clearance say that the area falls in seismic zone-IV, which is categorised as a severe intensity zone. Delhi falls in seismic zone-IV, which along with seismic zone-V is considered a ‘high seismic zone’. Seismically, zone-V is the most active and zone-II is the least, as per the Bureau of Indian Standards, which categorised the country into different seismic zones.

Going by the project summary submitted for environment clearance, the tunnel passes through the southern ridge, but not through the area marked as protected. The project will also pass through some agricultural land in the area.

The highway project is expected to decongest NH-48 in Mahipalpur and Rangpuri area. NH-48 carries traffic from Gurgaon to Vasant Kunj and Chhatarpur, as per the documents.

An official of the Forest Department said the proposal was yet to be submitted for clearance from the department, but an informal discussion was held with NHAI on the process that would have to be followed. The matter has also not come up yet for the Ridge Management Board’s approval, sources said.