Mukundara tunnel fills with water weeks after opening, NHAI admits flaws

India’s first eight-lane road tunnel, built beneath the Mukundara Hills Tiger Reserve in Rajasthan as part of the ambitious Delhi-Mumbai Expressway, has run into its first major test barely weeks after being opened on a trial basis.

Heavy rain over the past two days triggered waterlogging and seepage inside the 4.9-km Mukundara Hills Tunnel, causing severe traffic disruption and inconvenience to commuters. More significantly, an NHAI official has acknowledged that the original design assessment did not adequately anticipate the volume of water entering the tunnel during extreme weather.

The admission is likely to raise questions about the planning and execution of a project being showcased as an engineering and environmental landmark.

NHAI project director in Kota Sandeep Agrawal said inadequate pumping capacity was the primary reason for the water-logging and seepage. "The quantum of seepage water coming in is quite high, and the pumping capacity we had installed was insufficient. We are currently enhancing that capacity. This is the first rainy season since the tunnel's completion. During construction, the contractor's design assessment was applied, but it has proven inadequate for these conditions," Agrawal told PTI.

The tunnel currently has an installed pumping capacity of 260 HP, with another 130 HP on standby. Additional pumps are now being deployed to drain the accumulated water.

Agrawal described the shortcoming as a technical issue that would be rectified with higher-capacity equipment. But the episode comes against the backdrop of growing scrutiny of the quality of NHAI projects, particularly the adequacy of design, supervision and accountability.

In July 2025, Union road transport and highways minister Nitin Gadkari told the Rajya Sabha that 55 instances of collapse or structural damage had been reported in NHAI road, bridge and tunnel projects over the preceding five years. Forty of these occurred during construction and 15 in completed projects. While action was taken against private contractors in almost all cases, disciplinary action was taken against government officials in only two.

NHAI has also had to act against contractors over specific construction failures. In June 2025, it debarred a concessionaire after a slope protection structure on NH-66 in Kerala collapsed, with the ministry attributing the incident to improper design, inadequate slope protection and a poor drainage system. An expert committee was subsequently constituted to review the design and construction of NH-66 in the state.

The Comptroller and Auditor General has, over the years, flagged a separate but related problem: weaknesses at the planning and project-preparation stage. In an audit of NHAI's public-private partnership projects, the CAG found that NHAI incurred Rs 856.80 crore on changes in scope in 23 projects, of which Rs 662.53 crore was attributable to deficient Detailed Project Reports or feasibility reports. The audit also flagged delays that resulted in foregone toll revenue.

The Mukundara episode is therefore significant not merely because rain has disrupted traffic inside a new tunnel, but because the official explanation points directly to an inadequacy in the assessment that preceded its construction.

The tunnel is a crucial link in the 1,386-km Delhi-Mumbai Expressway, an eight-lane corridor being built at an estimated Rs 95,000 crore. The Mukundara Hills section was designed to carry the highway beneath the tiger reserve so that wildlife movement above the tunnel would not be disrupted by road traffic. The 4.9-km structure was opened on a trial basis to all vehicles on 27 July.

According to NHAI officials, the tunnel itself has cost around Rs 1,250 crore. Its environmental design was intended to allow animals to move freely above the structure while traffic passes below, making it an example of attempting to reconcile large-scale transport infrastructure with conservation.

Police officials said the water-logging severely affected traffic for more than an hour and a half. Vinod Samaria, SHO of Mandana police station, said pumps were being used to drain the tunnel, while engineers were working at the site.

Rajendra Meena, SHO of Modak police station, said additional police personnel had been deployed to regulate traffic at the other end of the tunnel. Vehicles were being allowed through one by one. He said water had not flooded the entire 4.9-km tunnel but had accumulated to a depth of about 1 to 2 feet along a stretch of more than a kilometre in the middle. Heavy rain, he said, had increased seepage from the forest above.

The timing is also noteworthy. The tunnel was opened only recently and this is its first monsoon, meaning the pumping system and the structure are now being tested under conditions that the original assessment apparently did not adequately provide for.

The episode comes at a time when Gadkari has also been a prominent voice in the government's push towards ethanol and flex-fuel vehicles, despite ethanol blending being a policy domain of the Ministry of Petroleum and Natural Gas. Petroleum minister Hardeep Singh Puri launched India's first flex-fuel passenger vehicle in June, with Gadkari present at the event.

The government has meanwhile said that no decision has been taken to raise the nationwide ethanol blending level beyond 20 per cent.

For Gadkari, whose tenure as road transport and highways minister has been closely associated with an aggressive expansion of the national highway network, the more immediate challenge remains closer to home: ensuring that the roads, bridges and tunnels being built at enormous public expense are designed adequately for the conditions in which they have to operate.

With PTI inputs