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Seismic strengthening and Structural Raising of the 1892 masonry Tansa Dam

Strengthening the Tansa Dam for Mumbai's water security

Seismic strengthening and Structural Raising of the 1892 masonry Tansa Dam

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Project Context

Built in 1892 to provide drinking water to Mumbai, the historic Tansa masonry dam in Thane required comprehensive structural retrofitting.

Following the 1993 Killari earthquake, updated safety reviews classified the aging asset as structurally vulnerable to a Maximum Credible Earthquake (MCE).

The Municipal Corporation of Greater Mumbai (MCGM) mandated an extensive stabilization framework involving downstream concrete buttresses to safeguard the city’s primary water lifeline.

Structural Reinforcement

01 / Structural Reinforcement

Continuous Operations

02 / Continuous Operations

Modernized Standards

03 / Modernized Standards

Execution Challenge

The primary execution constraint involved stabilizing a live, high-capacity reservoir without lowering water levels or disrupting municipal water transmission.

Geotechnical complexities on the Deccan Trap basaltic foundation demanded non-destructive anchoring techniques.

Working on an aging, high-consequence masonry structure meant that induced vibrations from traditional civil interventions threatened the dam's structural stability.

Additionally, seasonal monsoonal cycles restricted the active downstream construction window to narrow, non-rainy periods.

Strategic Role

Mr Avarrsekar led a bid strategy that aligned the company's marine and mass-concrete methods with MCGM's technical requirements, and set up governance and risk oversight for delivery.

As the senior interface with municipal engineers, he sped up design validation and material clearances, protecting progress from the administrative and public scrutiny attached to a critical water asset.

Actions Taken

- Formulated an accelerated mass-concrete deployment schedule for downstream buttress installation.

- Used zero-vibration drilling to anchor foundations into basalt.

- Monitored structural deflection in real time throughout execution.

- Managed multi-tier logistics to move heavy aggregate through sanctuary zones.

- Certified bonding with the legacy masonry through non-destructive testing.

Outcome

The successful installation of massive downstream concrete buttresses restored the dam’s stability to modern seismic requirements, ensuring complete water security for Mumbai.

The engineering turnaround validated how aligning complex technical competencies with rigid public sector procurement criteria mitigates critical infrastructural vulnerabilities.

For contemporary contractors, this success case illustrates how translating specialized engineering risks into structured tender responses drives high-margin business growth and predictable project handovers.

Technical Data of Record

Scope of Work

Strengthening and raising of the masonry gravity dam through downstream reinforced concrete buttresses, rock anchoring and interface pressure grouting.

Key Specifications & Challenge

Mass concrete buttresses, Deccan Trap rock anchors, low-heat cement with fly ash and epoxy and polymer-modified grouting. Works under full reservoir load, no blasting near 19th-century masonry, and logistics within a wildlife sanctuary.

Major Deliverables

A seismically stabilized dam, a complete buttress network, validated foundation anchorage and structural health instrumentation logs.

Result

Stability restored to modern seismic requirements, with monitoring by piezometers and ultrasonic joint-meters and 100% material testing and core sampling.

Client

Municipal Corporation of Greater Mumbai (MCGM)

Location

Tansa River, Thane District, Maharashtra, India

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