we have a 100 year old school building that has been converted into a community building and have what used to be a hatch for dropping coal down into basement has nowbeen concreted over at a 45 degree angle to wall and on inside ofcellar there are two paving flags on the underneath. how easy and what would be needed to be done to get rid of concrete and fill in to stop water running down building into cellar

many thanks

They used to fill old cellars with rubble if they were prone to flooding.

You could fill it with hardcore if you wanted to, I am just not sure if it is a good idea

You can get hardcore for free most of the time if you remove unwanted hardcore from other peoples building projects.