Environment Ministry panel clears new Sikkim dam despite its own concerns

On October 4, 2023, the South Lhonak glacial water successful Sikkim burst, causing a flood that Ministry sheet clears Sikkim dam operation contempt ain concerns killed 40 radical crossed 4 districts of Sikkim. The flood besides washed distant the 1,200 MW Teesta-III Chungthang Dam located 55 km downstream.

The EAC motion for the caller dam comes successful the backdrop of concerns the sheet had itself raised implicit the structure’s information and stability.

Late successful December 2024, an EAC sub-committee comprising the panel’s chairman, a Central Electricity Authority official, a elder ministry authoritative and an authoritative of the Central Water Commission (CWC) visited the tract to measure the readying and feasibility of the projected factual gravity dam successful spot of the earlier factual rock-filled dam.

A factual gravity dam is made wholly retired of factual and is mostly considered stronger than a factual rockfill dam, but is much costly to construct. A factual rockfill dam has a halfway of factual that is surrounded by rockfill material.

Days aft the December tract visit, astatine its gathering connected January 10, the EAC approved Sikkim Urja’s connection adjacent arsenic it noted – according to the minutes of the gathering of that time – that the “design directorate of CWC has suggested to transportation retired a revised survey of the PMF (probable maximum flood) and diversion flood and get it approved done acrophobic hydrology directorate of CWC”.

The EAC besides acceptable conditions for the caller dam – including the mounting up of aboriginal informing systems and the mapping of glacial lakes and landslide spots – portion noting that the plan aspects were yet to beryllium approved by the CWC, Geological Survey of India and the Central Soil and Materials Research Station.

Proposal documents and the minutes of the January 10 gathering showed that 1 of the cardinal concerns of the EAC was centred connected the capableness of the caller dam to withstand flooding successful the lawsuit of an incidental of the quality of the October 2023 GLOF. In its response, however, Sikkim Urja Ltd stated that the projected dam’s spillway capableness (which allows draining of excess water) has been enhanced from 7,000 cumec (cubic metre/second) to 19,946 cumec portion taking into information some eventualities — a probable maximum flood arsenic good arsenic different GLOF event.

Back successful the mid- to late-2000s, erstwhile the task was being appraised, it was warned that a debased spillway capableness risked overtopping, which is what yet happened erstwhile the South Lhonak water burst successful the aboriginal hours of October 4, 2023.

When the EAC asked Sikkim Urja astir the hazards of glacial lakes upstream, the institution claimed that of the 119 glacial lakes identified successful the catchment area, 50 large lakes, with an expanse of 10 hectares oregon more, were shortlisted for evaluation. “After a elaborate study, 13 perchance unsafe glacial lakes were identified based connected h2o dispersed country (40 ha oregon more), measurement and distance,” the institution submitted to the EAC. The EAC’s minutes did not specify who authored the survey connected the glacial lakes.

According to the minutes of the meeting, a“worst-case” script was worked retired utilizing antithetic combinations for GLOF events and it was calculated that a breach successful 2 lakes would merchandise a combined measurement of 109.44 cardinal cubic metres of h2o and the eventual GLOF flood worth would beryllium 12,946 cumecs. “The worth has been approved by CWC,” the institution submitted to the EAC.

Calls and messages by The Indian Express to EAC Chairman Professor Govind Chakrapani, seeking comments connected the panel’s decision, and to Yogendra Kumar, ED – Incharge and President, Sikkim Urja Limited, went unanswered.

An email sent to the Greenko Group seeking its effect connected the EAC’s decisions excessively did not elicit immoderate response. Promoted by the Sikkim authorities until past year, Andhra-based Greenko Group present owns the bulk involvement successful Sikkim Urja Limited.

Independent adept Himanshu Thakkar of the South Asia Network connected Dams, Rivers and People questioned the “hurry” successful clearing a task with a past of disaster, particularly erstwhile the revised probable maximum flood studies were awaited. “This connection should beryllium treated arsenic a caller connection successful the discourse of changing rainfall patterns, the GLOF vulnerabilities. The EAC should person ordered for a caller biology interaction appraisal erstwhile the Central Electricity Authority and CWC are considering it successful a caller way. They are besides utilizing aged information for floods by their ain admission. There should beryllium caller calculations for highest flood levels based connected caller data,” Thakkar said.

The EAC did not question a caller nationalist proceeding connected the grounds that nary caller onshore acquisition, displacement was progressive and due to the fact that a nationalist proceeding was conducted successful August 2006.