drainage for synthetic turf

https://page-wiki.win/index.php/Building_a_Greener_Yard_with_Eco-Friendly_Landscaping_Solutions

A good drainage system is what stops synthetic turf from turning into a swamp after a downpour. Modern fields use a permeable backing and a crushed stone base to let water filter straight through, so you don't get puddles or mold. It's not glamorous, but without it a nice fake grass lawn just becomes a muddy mess.