The construction is about ninety percent finished.
The preparations are nearly complete.
almost certainly; in all probability
Expresses a high degree of certainty about a future event or outcome; similar to 十中八九.
He will almost certainly come.
I think it will succeed in all probability.
A general adverb for 'almost' or 'nearly'; 九分通り is more specific to a high degree of completion or probability.
Compound of 九分 (kubu, 'nine parts') and 通り (dōri, 'as; in accordance with'), literally meaning 'as nine parts out of ten', hence 'ninety percent' or 'almost'.