How to construct a sewer through a landfill site? 3

[msalisonlacey]

Hi Guys,

I have an interesting problem I was hoping someone could help with me.

We have been asked to evaluate possible sewer construction methods through a landfill site. The landfill site comprises of fill which ranges in depth of 8 feet to 50 feet.

The fill is non compacted and consists of gravels, bricks, basalt cobbles, glass, metals and other domestic refuse including layers of leather.

The use of a gravity reticulated sewer system we are ruling out because of differential settlements concerns.

The water authority suggested we consider a rising main system using a flexible pump. The project is for the construction of 10 residential units.

The problem with a rising mains systems is that civil groups have opposed the use because of potential problems of electricity breaks would see the pumps inoperational. There are maintenance issues with pumps and the provision of emergency maintenance 24/7/365.

There are concerns if a breakdown or power failures occurs it could cause uncontrollable sewage flow to the private dwellings and to a local water way.

Has anyone had experience with anything like this? How would you approach it? Do you think a cast iron sewer main founded on driven treated pine piles into the natural ground below which provides a good bearing capacity is a cost effective viable solution.

Thanks for your time guys.

Allie.

 

[ishvaaag]

I think the pumped system is the way to go, since you have overall unreliable behaviour; for electricity breakdown, provide local generator backup.

 

[cvg]

construction on piles might be technically acceptable. but certainly very expensive which might make a force main more cost effective. Backup generator should always be provided for a force main. If you are going to design a force main, consider routing it around the landfill instead of over or through.

 

[apsix]

Is there a liner which will prevent the use of piles?

 

[msalisonlacey]

Hi apsix,

No there is no liner except for a clay capping type liner which will not interfere with piling.

Thanks!

 

[oldestguy]

Watch that you don't get methane following along settled pipes or non-settling pipes and fill tat settles. It may take special trench treatments away from the landfill.