NHAI defends use of pond land for building underpass near Mamallapuram, says road safety took priority

Chennai: The NHAI has told the National Green Tribunal (NGT) that it was compelled to use a portion of a pond in Mamallapuram for constructing an exit ramp as part of its East Coast Road four-laning project from Mamallapuram to Puducherry. The submission came in response to a petition alleging that the construction encroached upon the waterbody without proper justification.

National Highways Authority of India (NHAI) project director M S Chaitanya stated that 3,460 sqm — less than 20% of the 15,000-sqm pond — were used, all along the edge in shallow sections. This area was essential to provide access for vehicles entering Mamallapuram from the Puducherry side via a proposed underpass near the heritage elephant sculpture. According to the submission, the current junction is accident-prone, and the absence of a proper exit ramp could turn it into a blackspot on the high-speed corridor.

The national agency finalised the alignment in 2018, awarded the contract in March 2020, began work in May 2023, received an objection in August 2024, replied in two weeks, and noted the NGT case was filed only in January 2025.

NHAI cited a report from its independent engineer, LN Malviya Infra Projects, which confirmed that around 10,800 cubic metres of earthwork was undertaken within the pond area, using earth that is non-polluting. It clarified that the embankment would not impact water quality and that pond water would remain static regardless.

To offset the impact on the Solaipoigai tank, from which the pond land was taken, NHAI extracted earth from four other nearby lakes — Pooncherry, Perumaleri, Karanai, and Kuzhipandalam — totalling more than 45,000 cubic metres. This excavation, the agency said, increased water storage capacity in the region as part of its commitment to waterbody rejuvenation under the ‘Amrit Sarovar' initiative.

NHAI said it obtained a no objection certificate from the Tamil Nadu water resources department for the alignment and argued that alternative alignments were geometrically unfeasible due to proximity of a major bridge across Buckingham Canal, located just a kilometre away. Shifting the exit ramp further away, it said, would compromise road safety. The case will be heard again in June.