In Gandhinagar, the Gujarat State Dam Safety Organization has raised serious concerns about the structural integrity and safety of Demi III and Machhu II, two major dams in Morbi district, as well as identifying defects in at least eight other reservoirs across the state.
A report from the Gujarat State Dam Safety Organization for 2024-25, presented to the assembly on Friday, focuses on the structural safety of 524 "specified dams".
Regarding the Demi III dam, the report states that out of the 17 piers, five – namely 3, 6, 9, 12, and 14 – were the subject of detailed investigation.
The report details non-destructive tests, including UPV, GPR, and core extraction, as well as material property and chemical tests conducted on the piers. Specifically, ultrasonic multiarray tomography and GPR mapping were performed on piers 9 and 12.
The report found that the "concrete strength" from core tests was "poor, ranging from approximately 5 N/mm² to 14 N/mm², while a minimum requirement of 20 N/mm² was specified."
Core samples, except for pier number 12, showed "disintegrated concrete with separation of cement, sand, and aggregates." The report also noted that "extensive voids were present in the concrete."
Furthermore, the report indicated that "the depth of carbonation was greater than the concrete cover in many cases, suggesting potential corrosion of the reinforcement." pH values also indicated that the concrete was acidic, accelerating reinforcement corrosion. Geophysical investigations further confirmed poor concrete quality. GPR tests revealed excessive and irregular reinforcement spacing.
In the "actions taken" section, the report recommends that the "structural fitness of the entire dam should be assessed after conducting tests on the Ogee spillway, in consultation with the DSRP (Dam Safety Review Panel)."
At the Machhu II dam, a significant amount of leakage was found in the inspection gallery located in the additional spillway. The report recommends replacing all gates to ensure dam safety.
The report also notes that the replacement of all dam gate components is currently underway and planned to be completed before the monsoon season. A DSRP visit 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.
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 the abutments.
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 to make decisions on long-term restoration.
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 season under Long Term Rectification (LTR) works.
In the 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.
At the Kaila dam, flow concentration observed during the 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 CDO, Gandhinagar.
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 the monsoon, according to the report.
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 repair works will follow, as stated in the report.
In the 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 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. Replacement work is currently in progress.