Joshimath panel points to 'water from unknown source' for cracks

The expert panel's field assessment report on Joshimath has pointed out that sediment-laden water, gushing out of an unknown underground source, might have caused arcuate-shaped erosion and cracks as deep as 1 meter in several areas.

Water samples from the NTPC Tapovan-Vishnugad hydropower project site and the tunnel itself have been sent to the National Institute of Hydrology to assess for any possible linkage.

ET has learnt that experts are trying "to understand...role of tunnel" in the recent damages. The hydel project's tunnel has been surveyed by the team, which held discussions with the NTPC technical team on the progress of tunnel construction.

"It seems some underground water source burst by removing substantial earth material. This probably created some underground void...which is being manifested as sinking and subsidence in different spots above and below JP Colony. This has caused many large cracks, some more than 1 m deep," the report has said.

Their report shows damage is "mostly confined in an arcuate shape, starting from Sunil, the right limb goes through Ravigram and AT Nala, while the left limb goes through Manohar Bagh, Singhdhar, Marwari and JP Colony".

Following major cracks in several buildings, the impact of the under-construction hydel project and the Char Dham Pariyojana on the ecology and stability of Joshimath and its vicinity has come under serious scrutiny.

A seven-member panel was set up by the Uttarakhand government to conduct a field survey in Joshimath.

The panel, with experts from IIT Roorkee, Geological Survey of India, National Institute of Hydrology, and the Wadia Institute of Himalayan Geology, conducted the survey between January 5 and 6 and has submitted a draft report. A key observation is on the "major turbid water flow" from JP Colony to Marwari bridge, which aggravated on January 2. This coincides with cracks in several houses.

"This water flow is seen to be of approximately 400 lpm and is laden with sediment content giving a muddy appearance. This was said to be aggravated on the night of January 2, 2023. The gushing of the water flow and the appearance of aggravated cracks coincide," the report has said.

Silt content in water samples is being assessed. Due to this water flow, there is "uneven settlement of the ground" causing failure of retaining walls. Foundations of the buildings have also failed in several cases. The water source was yet to be ascertained, the panel is learnt to have said.

The survey says that in Ravigram, Gandhinagar, NTPC Colony, AT Nala and other areas, there are "no substantial new aggravated cracks". The cracks were observed last August too.

Reaffirming the previous reports, the panel said that "Joshimath is located over a thick cover of loose material and is witnessing gradual sinking for a long time". The loose material is observed almost in "all regions of the town".