We have planning permission for a two storey extension in Tooting which would require us digging below the level of the sewer that runs through the gardens in our terrace. Having spoken to Thames Water we know it can be moved but as yet haven't come across anyone who has had the work done or can find a structural engineer who has direct experience of figuring out how to do it and present plans to TW for sign off. Wondering if anyone has done anything similar. Our plans would also mean having a lower ground floor below garden level - also keen to know if anyone has had work like this done as again unable to find anyone we know with a lower ground floor level or a builder who has completed a similar project.
Any thoughts gratefully received. Thanks!