Problem: we can't build a soakaway because the water comes from the road and the whole road would have to be taken into account when calculating the size of the soakaway.
Solution: block the gulley on the road so we only have to build a soakaway big enough for the rain landing on our roof, which is also deposited into the pipe.
Problem: the council says that the pipe follows an old watercourse and we're not allowed to block up the gulley in the road.
Solution: unblock the drain and reline it.
Problem: the pipe is next to a hedge and is packed with roots; the pipe itself is actually just a bunch of short sections butted up against each other, there's no cement connecting the parts together. Sending a root-cutter down will probably collapse it.
Solution: build a new pipe from where the old one emerges out from under our house, following the general route of the old pipe.
Problem: we don't know where the old one goes.
This is where we've been for about three weeks. The past few weekends, I've been digging a trench in the garden hoping to find the pipe after the point at which it's blocked (which is about 25 metres from our house). Once found, the plan was to break into it and send a camera down to find out where it disgorges its contents. There's a ditch at the bottom of the garden, so it probably ends up there.
My hopes at finding the pipe came to nothing, though, despite my having dug a hole three feet deep and about 12 feet along.
Yesterday, the drain engineers came again. They managed to find the pipe at the point where it was blocked. It wasn't actually fully blocked there, as it happened: there was a lot of debris that had accumulated, but the blockage itself was further along. The reason it seemed to be a complete blockage was that instead of continuing in a straight line and bisecting my trench, the pipe takes a 90-degree left turn under our neighbours' property. It extends about 6 metres under their garden before it's completely blocked (or, I guess, makes another 90-degree turn). It may return to our garden, it may not: we don't know.
The neighbours weren't in, so the engineers had no access to the pipe from above. They tried to blast it clear of debris using high-pressure water jets, but to no avail. This means that we still don't know where the pipe goes, so we can't install a new pipe to replace it.
The council must have plans saying where the old watercourse is, or they couldn't stop us from blocking the pipe where it enters our property from the gulley in the road. If they show us these plans, we'll know to where we can run the new pipe. Finding someone who works for the council and who has access to the plans may be tricky though...
Oh, remember that high-pressure water hose the guys used? They sent 5 cubic metres of water down it. Guess where that water eventually seeped.
Yay! I have a moat!