Gandhinagar, February 28 – The Gujarat State Dam Safety Organization has raised serious structural and safety concerns regarding 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 by the Gujarat State Dam Safety Organization for 2024-25, which was presented to the assembly by the state government on Friday, focuses on the structural safety of 524 "specified dams".
Regarding the Demi III dam, the report stated that out of the 17 piers, five – namely 3, 6, 9, 12, and 14 – were subject to detailed investigation.
"Non-destructive tests, including UPV, GPR, core extraction, material property determination, and chemical tests, were conducted. Ultrasonic Multiarray Tomography tests were performed on piers 9 and 12, and GPR was used to map the reinforcement," the report stated.
According to the report, the "concrete strength" from core tests was found to be "poor, ranging from about 5 N/mm2 to 14 N/mm2, compared to the minimum requirement of 20 N/mm2".
Cores, except for pier number 12, showed "disintegrated concrete with separation of cement, sand, and aggregates," while in-situ tests indicated "extensive voids in the concrete," it said.
"There was a loss of binding material, the cement, and laboratory permeability tests showed the concrete to be 'porous'," the report added.
"The depth of carbonation was found to be more than the concrete cover in many cases, indicating potential corrosion of the reinforcement, while pH values indicate that the concrete is acidic, accelerating the corrosion of the reinforcement. Geophysical investigations also indicated that the concrete quality was poor. GPR tests showed excessive and irregular cover as well as erratic spacing of the reinforcement," it pointed out.
Regarding the action taken, the report stated that a comprehensive assessment of the entire dam's structural integrity will be conducted after testing the Ogee spillway, in consultation with the Dam Safety Review Panel (DSRP).
At the Machhu II dam, a significant amount of leakage was found in the inspection gallery of the additional spillway, and all gates need to be replaced as soon as possible for dam safety.
The report noted that replacement of all dam gate components is currently underway and is planned to be completed before the monsoon season.
A visit by the DSRP is scheduled to assess and address the leakage issue in the inspection gallery.
Regarding other dams, the Don dam experienced severe flooding during the 2024 monsoon, with approximately 3.60 meters of water over the spillway crest, causing "significant 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 level showed signs of settlement. Some drain holes were malfunctioning, and widened joints were observed between the spillway panels. Vertical cracks were also observed on the 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 Organisation is scheduled to make decisions on long-term restoration, the report noted.
At the Bharapar dam, "significant 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 the monsoon under Long Term Rectification (LTR) works, it said.
At the Khambhala dam, a "higher rate of seepage" was observed in the earthen dam along with minor cracks in the masonry pointing. A DSRP site visit is planned, and major repair works will be undertaken under its guidance, the report said.
"At the Kaila dam, flow concentration observed during monsoon in the downstream of the tail channel and gabion settlement due to erosion were reported. Cleaning of the tail channel and gabion protection work have been executed under the guidance of the Central Design Organisation (CDO), Gandhinagar," it said.
The Vengadi dam's bodywall and spillway apron were "heavily damaged in flood after the monsoon". Apron restoration has been completed, and repairs are underway before the monsoon, the report said.
At the Fodaraness dam, cracks were observed in the spillway body wall and longitudinal cracks on the earthen bund top. A DSRP visit is planned, and repairs will follow, it stated.
In the Manjal-Reladia dam, part of the body wall and apron from the right side of the waste weir had eroded.
The eroded portions have been rectified under ongoing LTR (Long Term Repair) works, as per the report.
At the 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, the report said, adding that replacement work was in progress.
