Gandhinagar, Feb 27 (PTI) The Gujarat State Dam Safety Organization has flagged serious structural and safety concerns in Demi III and Machhu II, two major dams in Morbi district, while also identifying defects in at least eight other reservoirs across the state.
A report of Gujarat State Dam Safety Organization for 2024-25, which was tabled in the assembly by the state government on Friday, focuses on the structural safety of 524 “specified dams”.
About the Demi III dam, the report said that out of 17 piers, five piers, namely 3, 6, 9, 12 and 14 were taken up for detailed investigation.
“Non-destructive tests such as UPV, GPR besides extraction of cores and determining material properties as well as chemical tests were conducted. Pier numbers 9 and 12 were subjected to Ultrasonic Multiarray Tomography test and mapping of reinforcement using GPR,” the report said.
As per the report, the “strength of concrete” from core tests was found to be “poor, varying from about 5 N/mm2 to 14 N/mm2 as against a minimum requirement of 20 N/mm2”.
Extracted cores, except in pier number 12, showed “disintegrated concrete with separation of cement, sand and aggregates”, while in-situ test indicated “extensive voids in the concrete”, it said.
There was “loss of binding material, the cement” and laboratory permeability tests showed concrete to be “porous”, the report added.
“The depth of carbonation is found to be more than the concrete cover in many cases indicating likely corrosion of reinforcement, while pH values indicate the concrete is acidic accelerating corrosion of reinforcement. Geophysical investigations also indicated the quality of concrete to be poor. GPR tests showed excessive and irregular cover as well as erratic spacing of reinforcement,” it pointed out.
In the “action taken” column, the report said the “structural fitness of the entire dam is to be assessed after conducting tests on the Ogee spillway, in consultation with the DSRP (Dam Safety Review Panel)”.
At Machhu II dam, a large amount of leakage was found in the inspection gallery located in the additional spillway, the report said, adding that all gates need to be replaced in the interest of dam safety as earliest.
The report noted that replacement of all dam gate components is currently underway and planned to be completed before the onset of the monsoon.
A visit by the DSRP is scheduled to assess and address the issue of leakages in the inspection gallery, it added.
Among other dams flagged, Don witnessed severe flooding during the 2024 monsoon, with about 3.60 metres of water over the spillway crest, causing “major damage to the spillway panels” over an area of nearly 25m x 25m, it said.
“The right-side wall and tail channel were affected by a landslide. The end sill blocks near the apron levels showed signs of settlement. Some drain holes were malfunctioning and widened joints were observed between spillway panels. Vertical cracks were also observed on abutments,” the report informed.
As short-term measures, concrete work in the chute spillway panel and right side wall has been completed. A joint visit by the DSRP and Central Design Organization is scheduled for decisions on long-term restoration, the report noted.
At Bharapar dam, “major damage” was found in the waste weir and the “curtain wall washed out”, while progressive deterioration was observed in the downstream tail channel.
Rectification is planned to be completed before monsoon under Long Term Rectification (LTR) works, it said.
In Khambhala dam, a “higher rate of seepage” was observed in the earthen dam along with minor cracks in masonry pointing. A DSRP site visit is planned and major repair works will be undertaken under its guidance, the report said.
“At Kaila dam, flow concentration observed during monsoon in the downstream of tail channel and gabion settlement due to erosion were reported. Cleaning of the tail channel and gabion protection work have been executed under guidance of the CDO, Gandhinagar,” it said.
The Vengadi dam’s bodywall and spillway apron were “heavily damaged in flood after monsoon”. Apron restoration has been completed and repairs are underway before monsoon, said the report.
At Fodaraness dam, cracks were observed in the spillway body wall and longitudinal cracks on the earthen bund top. A DSRP visit is planned and repair works will follow, the report said.
In Manjal-Reladia dam, part of the body wall and apron from the right side of the waste weir were eroded.
The eroded portions have been rectified under ongoing LTR (Long Term Repair) works, as per the report.
At Malan dam, corrosion was found in the support leg of the automatic gate and damage to the fulcrum channel joint, reducing efficiency and design life, said the report, adding that replacement work was in progress. PTI PJT PD BNM
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