Sub-divide with an easement

@Westminster have you explored or heard sewer lining being used so that you can build over the sewer? Not on small jobs like this one but larger builds or commercial/industrial?
I have done a few jobs over east for commercial/industrial developers and water authorities ok'd lining (with design approval) instead on conc encasement. A lot cheaper and easier

Might be something to keep in mind for the bigger jobs

 

How does that impact on the capacity of the pipe? (Smaller diameter requires greater fall).

 

There's a few different brands but for a 150 pipe its about 8mm thick. So new diameter 134mm but the benefits of "new pipe", smoother wall, another 50 years of life or weigh the loss of dia. ....but will pose a problem in the future but with advances in technology etc shouldn't be a problem (ie someone else's! )

If grade is to flat you'd be better to look to pipe bursting so you get a new PE pipe plus bigger dia. Down fall is you have to dig each junction to cut open and re connect

 

I've never heard of it - and I don't really understand what it is. Can you explain or link?

 

There's a few different brands and products but this is a very general video of how it works


For development jobs you could use relining so you can build over the sewer, but depends on the water authority

 

Hmmm thanks for that - learn something new every day. I suspect I am only allowed to encase but I will double check.

 

Keep it up your sleeve for a bigger job. Might buy you a few extra crucial metres