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Accelerating Breakwater Construction

Mangalore Coastal Protection Contractor Builds Offshore Reefs with Speed and Accuracy

Customer Profile: DVP Infra Projects Pvt Ltd. is a civil contractor that specializes in marine construction. Based in Mumbai, India, the company has been a leading constructor of ports, jetties, breakwaters, harbors, wharfs, roads, bridges and marinas in the region. Geometry Construction Co. is a Hyderabad, India-based construction company that specializes in coastal erosion protection works offering both hard and soft solutions.

Business Challenge: As part of the Mangalore Coastal Protection Project, the joint venture team of DVP Infra Projects Pvt Ltd. and Geometry Construction Co. were contracted to construct two offshore reefs to stabilize the shoreline.

Solutions:

  • Trimble Marine Construction system for block placement using wire cranes

​Benefits

  • Placed average of 200 tetrapods/day (versus target 50/day)
  • Achieved centimeter accuracy in x, y, z coordinates (versus traditional workflows of ˃30 cm)
  • Limited need for divers to check work in dangerous conditions
  • Completed project in 3 months (versus projected 6.5 months)

Port and breakwall

Located on the Arabian Sea, the port city of Mangalore in the Indian state of Karnataka faced a severe coastal erosion problem that posed an imminent threat to port operations and waterfront property. In response, the Asian Development Bank (ADB) funded the Mangalore Coastal Protection Project to restore and protect the shoreline.

As part of this effort, the joint venture team of marine construction specialist DVP Infra Projects Pvt Ltd. and coastal erosion contractor Geometry Construction Co. (DVP-Geometry JV) was tasked with restoring the area around the port city. The DVP-Geometry JV constructed two 250-meter-long artificial offshore reefs located about 600 meters from the shore to stabilize the shoreline and replenish the beaches.

To complete the job, DVP-Geometry JV operators used two wire cranes to place 6,500 tetrapods—5,250 6-ton tetrapods and 1,250 10-ton tetrapods—along with armor rock.

Crane placing tetrapod

Positioning the tetrapods per the design specification is typically a time consuming and labor-intensive effort that requires operators and divers to deal with turbid water, and often, significant wave motion. Using traditional methods, crews would place tetrapods with a margin of error of 50 cm horizontally and 30 cm vertically.

“Water turbidity limits our operators’ and divers’ ability to position and check the placement of the tetrapods, which sit as deep as 7 meters below sea level,” said Mr. Jafar Patel, Operations Head-Marine Projects at DVP Infra Projects Pvt Ltd. “Visibility is typically less than a meter, and the weather in this area is unpredictable. We were looking for a way to reduce risk to our team and improve efficiency.”

Per the project owner, the DVP-Geometry JV had six months to complete the project.

Tablet in machine cab

Filling the Gaps
Ordinarily, DVP-Geometry JV operators would vertically position the tetrapods using a reference paint mark on the crane wire.

“When we started the project, the client, stakeholders, owners and even our team were doubtful as to whether we would be able to complete the project in the favorable season,” said Mr. Patel. “Then Pan India stepped up.”

Working with Pan India Consultants Pvt. Ltd., the local Trimble marine solutions dealer, the DVP-Geometry JV evaluated the Trimble Marine Construction visualization solution. The platform includes Trimble Marine Construction software and a MPS865 Marine GNSS receiver installed on the wire crane’s RTK base station to locate the tetrapods relative to the design in 3D.

“Initially, we had six divers on the project checking placement and monitoring the gaps between tetrapods because we were apprehensive about the value of the Trimble Marine Construction software in a deep-sea operation such as this,” said Mr. Patel. “Within one week, our opinion totally changed.”

Tablet showing tetrapod placement

Saving Time/Raising Accuracy
The original owner-defined target was for DVP-Geometry JV crews to place 50 tetrapods per day. With a Trimble Marine Construction system, the operators averaged 200 tetrapods per day, and even set a record for 235 in one day.

“We also achieved centimeter level accuracy in x, y and z coordinates—so there was no need for divers on the job anymore. In addition, we were no longer limited to daytime work, so we worked two, nine-hour shifts,” confirmed Mr. Patel.

Subsequently, the DVP-Geometry JV completed the reef construction in just three months, better than 50% faster than initial projections.

Mr. Patel said, “The value of the technology went far beyond our imagination. This was a challenging project—and Trimble Marine Construction software made it easy, simple and safe. We estimate that we covered the cost of the system in 15 days.”

Mr. D.V. Raman, Managing Director at Geometry Construction, said, “The Trimble Marine Construction system enhanced our rock and tetrapod placement to the desired accuracy. By use of Trimble technology, we have expanded our operations to operate around the clock, which resulted in early completion.”

The owner was equally pleased. “The use of the Trimble Marine Construction visualization solution helped in timely completion of the project,” said Mr. Gopal Naik, Project Director for the Department of Water Ports and Inland Water Transport, Government of Karnataka.

When asked about advice to other contractors, Mr. Patel quickly stated, “The system provides a competitive advantage. We can be more aggressive in our tenders because the improvement in accuracy and time is a game-changer. Without any doubt, I would recommend it to other marine contractors.”