Lawn drainage solution?
I'm looking for a bit of help in deciding what to do about the drainage issue in my garden. We moved into a new house over the winter and quickly realised that there are significant issues with drainage in the back garden, particularly the lawn. It is quite a large lawn (approx. 60 feet by 60 feet) and is basically solid clay. The previous owners of the house had a French drain system installed at some point in the past (probably about 30 years ago I expect) but this seems to be doing little to improve the situation. The lawn was squelchy all through the winter and is only now (mid April) beginning to dry out. Even today it is a bit boggy in places even though we have had no rain for 10 days. There is lots of moss and weeds but even after scarifying the grass doesn't seem to want to grow.
I've sought the advice of a local landscape gardener who advertises drainage services and he has suggested the radical solution of:
1. digging up the top layer of clay from the whole lawn
2. building three new French drain channels down the garden leading to soakaways beyond the lawn
3. laying a six inch layer of stone chippings on the whole of the excavated lawn, covered with about 4 inches of new, good quality topsoil and then turf on top.
This is obviously going to be an expensive option but we are keen to get it right so that both we and out kids can enjoy the garden fully. So my questions are:
1. is this likely to work effectively?
2. is 4 inches of soil on top of gravel sufficient or will this actually be too effective and lead to the lawn drying out excessively in the summer?
3. any other problems that anyone can see with this solution?
Thanks for any advice you can offer!