Don't know about that. But you might put a plant container of some kind over it, supporting it clear of the ground with whatever seems convenient.

Hi s house and I put a large flower tub over it. The kids enjoyed planting it up twice a year and no roots got into the drains.

Thanks...It is right by my swing set so I can't put a planter any other suggestions? Would the sedum Matt hurt the drain?

cant you just make up a square of decking to cover it in a circle maybe . if you put plants down you will have issues including if they need to open it .

Well I've no experience of Sedum mats but normally water takes the easy route, which I would guess in this case would be round the mat rather than through it.

Could you not move the seat away from the drain?