Why not to use backpack blower?
This monster could blow your mind!
I have a range of electric power , battery and petrol Makita.
But this backpack I bought specifically for sucking job, not blowing.
When digging 2 to 3 meter deep, 46 cm wide holes in the ground for retaining walls I use my electric auger and the suck dirt into 200l metal drum. Easy pizy.
Eventually I finish with electric blower, sucker monster that you could consider too if you have access to 240v.
The main reason for efficiency here is size of turbine rotor.
Those on backpack and my electric blower sucker ARE HUGE.
That make them almost noise less,
But wind created is hurricane force.
Backpack is very cheap, you could possibly also use on the water yo propel you on windless day like jet engine.

If you got this path, sucking not blowing you could save yourself a lot of time. Because instead of moving dirt from one place to another you have all sucked in. My sucker accept everything from dirt, stones , rocks to leaves and small elephants.
I use 60 l barrel to centrifugal separate dirt from air . Pipe, hose 50 to 100mm.

I need to use double, one inside another plastic barrel becouse sucking force squize them flat.
Then remember the smaller blower sucker is the noiser is too. Like everything in life .