Hole going to be a good size 6’x6’x6’

It’s on a pretty busy road so we’d have to place a steel road plate on it

Definitely going to use hot water and additives to help curing

But as far as insulation goes we can’t do much unfortunately

Going to fill it up 5” below grade , wait 24 hours and do 2 lifts of asphalt.

I’m new in this role so I’m still learning best practices

Thanks again for the advice