Dip In Grass

Must be going bonkers ,the post before this one enquiring about Wilcos grass seed for some reason I thought I was in the General Discussion forum and could of asked the question as I was already in the Lawn forum . Not sure if I read on the web or this forum but I filled a dip on lawn last year and really tamped the earth down or so I thought but it has sunk again. Admittedly it is on about 1 ft square but how do I go about raising the level again.
Do I put fresh earth on top of the grass already growing in dip and scatter some fresh seeds down or do I start again, take up old grass, level with earth then scatter new grass seeds??

 

can I ask , is it a new lawn ? and whats underneath thats making it drop ?

 

Rather than putting soil on top (which will require seeding and/or the grass growing through) you could cut H-shaped slits in the lawn, where the dip is (or a hump for that matter), peel back the turf on either side of the cross-slit, put some soil underneath, then roll the turf back and press it down well so that it makes contact with the soil. Water in dry weather for 4 weeks to give the turf roots time to grow back into the soil below.

But as Spruce asks, you need to find what's causing it to sink. Although it may just be that there wasn't enough soil put in the hollow last year and its compressed enough to still leave a small depression?