There is no easy way to address these problems, and if its a local authority drain, they will be obliged to sort it out as there is a significant health problem.
However local authorities are not flush with cash at the moment and will may not be in a rush to carry out work involving significant outlays.
I suspect yours is a private drain, one that has never been taken in charge, and the local authority may either have no responsibility or may disavow even knowledge of the drain.
In that case I would advise you to engage a building professional, preferably a civil engineer to advise and inspect the opening up works - not cheap, but then underground work seldom is.
The underlying problems in such cases have several causes resulting on more groundwater arriving at this point due to
- additional rainfall surcharging all sewers and coming out at a weak point
- building works/hard surfaces accelerating surface water run off
- damaged or blocked pipework downstream of the last manhole
- blocked outfall further away backing up the entire system.
Things to look out for include
- new houses or extension built over the run of manholes
- trees or hedges along or near the line of the pipe - roots problem.
- builders traffic and parking locally leading to settlement of roads and paths.
If a blockage is the cause, and its a private drain, you may need to retain the services a drain clearance company who may have to undertake a CCTV survey of the line, if they cannot clear the blockage.
When the location of the blockage or damaged pipe is known, you will have to arrange for the section of pipe to be opened up and cleared and or replaced and the damage repaired.
The CCTV footage helps identify the nature of the problem and its exact location - holes in the ground can be expensive things to build.
Hope this helps.
ONQ.
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All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.