HYDERABAD: The National Dam Safety Authority (NDSA), in its final report on the Kaleshwaram Lift Irrigation Scheme (KLIS), has recommended the preparation of a rehabilitation design for the Medigadda, Annaram and Sundilla barrages. It also said that Block 7 of Medigadda has suffered irreversible damage.
“Based on inferences drawn from various investigations and studies, a suitable rehabilitation plan must be designed and implemented. The Committee recommends that the Irrigation department engage reputed institutions and departments for these tasks. Given the design complexities, the rehabilitation design should preferably be reviewed by the Central Water Commission,” the report stated.
The final report, spanning 378 pages and 16 chapters, notes in its “Recommendations on the way forward” that issues such as sand piping, cavity formation beneath the raft, construction flaws, and design deficiencies—already observed in Block 7 of the Medigadda barrage—could also affect other blocks.
‘Kaleshwaram construction began before DPR received greenlight’
The upstream barrages, Annaram and Sundilla, which exhibit similar design and construction flaws, have experienced structural distress and damage, rendering them unserviceable. “All three barrages require comprehensive investigation from multiple angles.
Investigations must remain unbiased and prioritise engineering standards. As the detailed rehabilitation design falls outside the scope of this Committee, a plan should be developed and implemented accordingly,” the report added.
Block 7 of Medigadda barrage has suffered irreversible damage with cracked and displaced piers and rafts. The Committee recommends that this block not be used for gate operations again. It may either be safely decommissioned or stabilised in-situ, without affecting adjacent blocks, it said. Cavities beneath the raft must be completely filled. As this could alter the foundation conditions, a fresh structural analysis using FEM software, considering soil-structure interaction, is advised.
Instrumentation should be installed across the barrage—three piezometers per bay at the upstream, middle and downstream points. Other instruments proposed in the rehabilitation plan must also be included. Continuous monitoring of data is essential to detect abnormal structural behaviour early.
The rehabilitation plan should also cover operation and maintenance protocols.
Causes of barrage failure
Lack of a proper Operation and Maintenance (O&M) manual has adversely affected the functioning of hydro-mechanical components at the Medigadda, Annaram and Sundilla barrages, contributing to their respective failures.
At Medigadda, inadequate maintenance was one of the contributing factors to the structure’s failure. In Annaram, the absence of proper O&M led to the worsening of piping and downstream erosion. Sundilla experienced similar conditions, resulting in downstream damage and structural distress.
Reason for Block 7 failure
Block 7 sank due to large cavities beneath the raft, caused by soil particle erosion through piping action. Piping occurs when seepage exit gradient surpasses safe limits, which are based on particle size and seepage path.
Pending appraisal
Construction of all three barrages began while the Kaleshwaram project’s DPR was still under appraisal by the Central Water Commission and other central agencies. The Irrigation department made substantial deviations from approved project parameters.
Notably, the decision to relocate Annaram and Sundilla barrages was made without upfront geotechnical investigations. The design flood value considered for the Sundilla barrage was lower than the CWC-approved figure.
General recommendations
The NDSA made specific recommendations for the three barrages and offered general suggestions to avoid recurrence:
Comprehensive geotechnical investigations should be mandatory for large-scale projects. These should identify foundation variability and enable detailed settlement analysis.
Use of finite element modelling is necessary for design, allowing stress, seepage, and deformation analysis under various conditions.
Timely data inputs must be provided for hydraulic and structural design. Delays compromise design accuracy. For instance, some drawings for Medigadda were released despite pending studies—a practice not suited to major projects.
The Central Design Organisation (CDO) currently has no role in planning, site investigations or ensuring proper execution. Frequent coordination between the CDO and construction units is essential. For example, the Gauge-Discharge curve—crucial for design—remained unverified by both the construction and CDO units.
An independent quality control unit must be established and not report to the construction unit. Posts should be filled rather than merely sanctioned to ensure effective quality control.
Third-party quality assurance is vital for ensuring construction integrity.
Project-specific O&M manuals are required. Regular maintenance following a documented protocol can prolong project lifespan. Dam/barrage owners must maintain and follow such manuals under a life cycle management approach.