I have a septic tank at the bottom of the garden which has a water out flow into a drain (I think this is a catch-pit or silt trap, its about 0.5metre square and 1metre deep empty chamber with cast iron drain lid). From the catch-pit the water is supposed to drain into an underground soakaway in the neighbours field.
I have noticed that when heavy rain occurs the water gushes out of the catch-pit drain lid. Also a foot square area of the garden about 4-5feet away from the catch-pit has turned to mud (so much so that if I stand on it the whole grass in that square foot or so bounces up/down and mud squelches out).
I have guessed that the catch-pit has filled up entirely with water and presumably this means the drain to the soakaway is blocked? I have tried to clear things by pouring SepticShock (septic tank conditioning bacteria) into the system.
What are my options?
2) lay new drains?
3) build a new soakaway beside the catch-pit?
How much might this cost?
Any suitable companies/engineers in the south Edinburgh/Glasgow region I might try for an assessment?