The Ministry of Shipping (MoS) announced new guidelines for dredging projects at major ports in November 2015. At present, major ports follow a number of different practices for the award of dredging works. Dredging contracts are awarded with payments linked to the quantity dredged based on pre- and post-dredging depths, guaranteed depth, hopper measurement of the dredger and daily dredger hire charges. These guidelines are thus required to ensure uniformity in practices prevailing at different ports.
Further, substantial dredging requirements are expected to come up with the implementation of the Sagarmala project, the plans to increase draught in inland waterways to 3-3.5 metres (from around 1 metre at present) and the proposal to augment capacity at ports to 3,000 million tonnes per annum (mtpa) by 2025 (from around 1,200 mtpa at present). Dredging will be an important component of these plans and the new guidelines will help facilitate project execution.
The key aspects of the guidelines are discussed below:
Pre-dredging surveys/investigations
As per the guidelines, geotechnical and geophysical investigations of the seabed need to be carried out to identify the type of soil and rock to be dredged. Defining physical and mechanical properties like particle size, bulk density standard penetration test value, etc. is also required. Further, bathymetric surveys are necessary to define water depths in and around dredging areas and disposal sites.
The government plans to develop three new ports at Vadhawan, Colachel and Sagar. For these projects, special attention needs to be given to survey and investigation as no prior data is available. The pre- and post-survey for the new ports includes topography survey of the area, bathymetric survey, geological desk study, geotechnical investigations of the seabed and investigations of environmental conditions. The selection of disposal area (offshore or onshore reclamation) for dredged material also needs to be looked into.
Long-term dredging contracts
In the guidelines, long-term contracts (five years) for maintenance dredging have been suggested. Among the major ports, the depth-based dredging contract can be adopted in ports like Kolkata, Cochin and Kandla, where sufficient data from previous years is available, dredging is required throughout the year and the contract can be linked with an incentive and disincentive mode of payment for guaranteeing depth.
Engagement of project management consultants (PMCs)
Ports can engage PMCs if the cost of capital dredging is over Rs 2 billion. The PMC’s role is to undertake comprehensive supervision of the project and they are supposed to be the “engineers” for the project. PMCs will study survey reports, detailed project reports/feasibility reports, etc., that are available with the port, prepare the bill of quantities, finalise tender documents, assist in invitation of bids, make recommendations for the award of work, initiate action for handing over the site, and scrutinise and approve dredging methods proposed by the contractor.
Pre-qualification criteria for dredging firms
Criteria have been fixed for the pre-qualification of firms. These include the experience of having successfully undertaken similar dredging works during the past seven years – three similar works, each work not less than 30 per cent of the estimated cost/quantity of the work tendered, two similar works, each work not less than 40 per cent of the estimated cost/quantity of the work tendered and one similar work of not less than 60 per cent of the estimated cost/quantity of the work tendered. Each port will have to indicate the exact mix of various types of materials to be dredged so that contractors can bid accordingly, while satisfying the eligibility criteria on the basis of quantity.
Assessment of dredging quantum
For different types of soil, different practices need to be followed. The triangulated irregular network methodology can be adopted for harsh rocky terrain, while the hyperbolic volume methodology could yield better results in the case of smooth-bottom topography like sand. The cell average method will be considered for sound reduction using a mapper tool in Hypack (hydrographic survey and processing software) and averaging is to be done with similar tools in other software while processing either single-beam or multi-beam survey data.
Dispute resolution in dredging contracts
The guidelines include suitable clauses for any change in environmental conditions, to avoid delays in payment to the contractor and for proper interface between the contractor and the port. It also specifies that contractual clauses, especially technical specifications, should be fair to both the client and the contractor.
The way forward
The guidelines aim to bring clarity to various issues that have resulted in dispute and arbitration and have thus delayed dredging projects in the past. Some recommendations for the future are teh adoption of the nautical depth concept, training for dredger maintenance, project management and hydrographic surveys, etc. and the strengthening of survey divisions of ports. w
Based on a presentation by H.N. Aswath, Director, Engineering, Ministry of Shipping
