5 Top Tips to improve your dredging production estimate

Production estimates are required to be able to price a new project and make a planning for it. But making an accurate production estimate for a dredger is quite a challenging task. With the below 5 Top Tips you can improve your estimate’s accuracy.

Top tip 1. Work backwards

By working backwards you can quickly establish the production that is required to complete the project in the allotted time. Simply divide the total project volume by the number of weeks available to complete the project. This will give a weekly production that needs to be achieved.

A project of 1 Million m3 that needs to be finished in 10 weeks requires a production of 100,000 m3/wk. If you can work 24/7 the hourly production must be 100,000/(24*7) = 595 m3/Hr.

Making these calculations will quickly show whether you can finish the project with one vessel or need more. Or you can determine whether your vessel size is suitable for the project.

Top tip 2. Build bottom up

Build an estimate bottom up by starting from small components and work towards a weekly production.

For example, for a CSD you can put in a face height, step size, swing speed and spill percentage. By using these parameters you can calculate the bulk production when swinging. Then add the time lost in corners, time lost for spud changes after a certain amount of swings and so forth.

By building the estimate in this manner you get a more realistic production estimate that is based on the actual dredging process of the vessel.

If one of the input values of the calculation changes you can quickly see the impact on the weekly production.

Top tip 3. Use previous production data

Use production data from previous projects as input to your new estimate. Don’t blindly copy the weekly production, but pick and choose. Analyse the previous projects and determine which parts of the project are similar to your current project.

If the soil is very different then a lot of the bulk production values can’t be used, but perhaps you can still use the time lost due to technical delays.

For example, for a TSHD you might be able to use the loading time, if the soil is similar. But if the sailing distance is very different you can’t use that part of the project data.

By smartly selecting bits and pieces from previous projects you can build your new estimate much more accurate.

Top tip 4. Break project in chunks

Instead of trying to estimate the whole project in one effort, break it up in meaningful pieces. If the project has two soil types make a separate production estimate for each soil type. By comparing the volume for each soil type against the production for each you can determine how much time will be spend on each type of soil.

Other useful splits can be discharge distances, dredge depths, high/low tide if the tidal difference has an impact and so on.

By making these splits you can make a more accurate estimate for each chunk which in turn will improve the accuracy of the production estimate for the complete project.

Top tip 5. Use soil data

Always base an estimate on soil parameters. Preferably from real measurements on the actual project, but if those are not available make educated guesses about them. Perhaps there is soil data available from a nearby dredging project or you have dredged in the area before. Even geological maps can provide some insight in what kind of soil might be expected.

Whatever the source of the soil parameters, clearly define them in your estimate. For example, this estimate is for Compacted Sand with an average grain size of 200 µm. The more detailed you provide the input for the estimate the more accurate the estimate will be.

 

These tips will improve your estimating accuracy, but they only scratch the surface. There is a lot more going on if you really want to get a high accuracy. Share your best tip for getting a more accurate estimate in the below comments section.

 

To your long term great results,
Timon Vinke

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