If I read your measurements correctly, you’re talking about digging up over 350 million cubic metres of soil and rock, transporting them 15km and dumping them safely. Comparing that to the cost of paying the land owners gives you a budget of approximately $0.20 per cubic metre. Ignoring the digging costs, you’d have to check what your local rates for trucking bulk soil would be over that distance, but I suspect they’re more than that on their own.

Then you have the rather signicicant issue of what to do with the literal mountain of soil and rock you need to dispose of. Just dumping it is going to cause pretty serious changes to the local environment, not least of which would be a new mountain.

Narwhals, Narwhals swimming in the ocean.
Causing a commotion.
'Cos they are so awesome!

With thanks to Weebl’s Stuff

Why, yes, my pop culture references are right up to date, thanks for noticing.

Two roads diverged in a yellow wood,
And sorry I could not travel both
And be one traveler, long I stood
And looked down one as far as I could
To where it bent in the undergrowth;

• Robert Frost