Pumping Down Hill 1

[TOHSEngineer]

I'm designing a small pavilion site with a parking lot and bathroom in a remote part of my town. The site is located on top of a hill. At the bottom of the hill there is a stream and on the other side of the stream is the sewer manhole I will be tying into. I was planning on using a grinder pump at the pavilion to pump the sewage downhill, under the stream and back up a few feet to tie into the manhole.

I have designed pump stations before but they were always at a low point and pumped against gravity. What considerations do I need to consider when pumping downhill? The distance from the pavilion to the stream is approx 1300LF with an elevation difference of 80'. Attached is a rough sketch of the project.

Over the past few years I have done limited utility work and am feeling a bit rusty on this one. Thanks in advanvce for any words of wisdom.

 

[Spartan5]

I would recommend a Septic Tank Effluent Pump (STEP) or Septic Tank Effluent Gravity (STEG) system.

Install at the pavilion a watertight 1,500 gallon 2-compartment septic tank with a filtered pump vault and 1/2 HP, 10 GPM pump (make sure to include an anti-siphon valve). Pump the filtered effluent via a 1-1/2" force main to your gravity manhole.

If you can convince the governing bodies that it would work, you could even omit the pump and just run a straight STEG variable grade sewer. There are effluent filters that offer 1/16" filtration and drawing from the clear zone of properly sized septic tank would prevent clogging issues. I would install a cleanout at the belly to allow for rodding or pressure cleaning of the sewer for peace of mind though.

If you have problems convincing a governing body that a STEG system would work in the this situation, you can let them know that it is a simple matter to convert a STEG system to a STEP system if problems arise. Just pull the effluent filter and drop in an filtered pump vault and controls.

Orenco Systems Inc. is a great source of reliable, well designed equipment for these sorts of projects.

 

[bimr]

Presentation that shows the alternatives is at this site:

http://aowatc.uwa.edu/Collection Systems.ppt#257,2,Sewer

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