“The stadium was built on a swamp,” he said. “There was soil that was compressed to provide an impermeable layer and after that we laid down 400mm of gravel for drainage, 300mm of sand and then about 40mm of turf."
The obvious questions to me are how hard do you need to make soil before water can't pass through it at all? Like, concrete hard?
And second, how does that compare to other grounds and does it make any difference? If you had soil all the way down to the bedrock, does that feel any softer to run on than 1m of soil over concrete? If you're using a penetrometer to measure firmness, then I guess the assumption is it's only the first meter (or less) that is important. Is that true?