I think that perhaps you are approaching the problem from the wrong perpective. In short, there are no hard and fast numbers, or even any real "rules of thumb" to assist you.
Firstly, and I am assuming that this is a given, is that you have a complete understanding of the project. In other words, you have done the geotechnical and design and understand what needs to be done.
Secondly, now you have to think as a potential "contractor". You will have to assess how the project is to be tendered (locally, regionaly, nationally) and from that point try to estimate the availability (and size) of earthmoving equipment.
Thridly, now will be the task to reasonably estimate how the job is to be done. By this, you will have to develop a methodology and think about how the most competative bidder would do the job. I have awarded low bids to contractors whom have work 24 hour shifts to complete earthwork components of highway construction. 200,000 yd3 may or may not be a monumental task, but it will depend on local conditions and equipment. If there is a completion date, then it will make things a bit easier, but if you are trying to determine a reasonable completion date, then I suggest using my method.
It also would be advantageous to sit down and speak with a few contractors on their ideas or approach. You may get some valuable insight for your purposes.
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