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someengineer (Structural) (OP)
15 Jul 09 14:56
Hello,

I am wondering if anyone has any experience designing lake water intake systems.  I have a shallow lake that freezes over the winter that I need to draw 2000m^3/day from.  We were thinking a stilling well on the bank of the lake with a pipe running into the lake from below the surface.

Does anyone have any experience designing any systems like this?

Thanks!
cvg (Civil/Environmental)
15 Jul 09 15:03
what's your question?
someengineer (Structural) (OP)
15 Jul 09 16:08
I was just curious if anyone had done a project such as this so that I could pick their brain. I want to find out what has worked in the past with lakes that freeze over. We were exploring the option of using an external stilling well or possibly a floating pump mounted barge system.

I don't suppose I have a specific question.  As the job proceeds questions will arise I'm sure.

  

 
Artisi (Mechanical)
16 Jul 09 1:13
Wouldn't your stilling well aslo freeze and how will a  floating pump float on a frozen lake?
StephenA (Civil/Environmental)
16 Jul 09 3:11
The pipe into the lake system is close to industrial systems for desalination plants.

One problem is growth inside the pipe. With fresh nutrients flowing past all the time there is a build up. In desalination plants there is a hypochlorite injection point offshore to kill the growth.

You would also need an intake structure and grid to avoid sucking up fish. A figure of 0.2m/s for flow rates is quoted so that fish can swim away but this may depend on fish size.

A job we are looking at presently in the sea has a electronic fish repelling system.

Hope this helps.

Stephen Argles
Land & Marine
www.landandmarine.com

MikeHalloran (Mechanical)
16 Jul 09 7:47
The schooling behavior of fish will keep them out of an intake, so long as the flow is horizontal, and slow enough that they _can_ swim away from it.

The grid is needed to exclude humans and other trash.

 

Mike Halloran
Pembroke Pines, FL, USA

Helpful Member!  SNORGY (Mechanical)
16 Jul 09 8:49
I have done a river water intake using a wet well, intake gallery and submersible electic encapsulated-motor type pumps, valves, piping and controls.  I have also done systems with individual wet well pumps (Red Arrow as I recall) for water injection (waterflood) EOR applications.  I have also seen the styles referred to here with the intake trash screens and - when required - water treatment.  If there is current at all, I am inclined to use some form of wet well + intake concept on shore.  It's less invasive, less prone to break-up damage, easier to maintain, and not as much an eyesore in environmentally sensitive areas.  (i.e., you can plant bushes around it so the guy fishing in the boat doesn't even know it's there.)

Just my opinions.
 

Regards,

SNORGY.

SNORGY (Mechanical)
16 Jul 09 8:56
Sorry...having said the above...

The biggest issue I have had is with solids loading.  If you are piping into a pipeline, for example, you can silt up pretty quickly without filtration.  In one application, to deliver water filtered down to 100 microns, we calculated an annual operating cost - in filter element replacement / maintenance alone - of $84,000.00.  Make sure you get a good water analysis and plan accordingly.

Regards,

SNORGY.

someengineer (Structural) (OP)
16 Jul 09 11:14
Thanks for the responses,

We are looking into ways to avoid excessive solids from entering the system. The lake that we are tapping into is fairly small and secluded and we are getting a survey of the lakebed and associated geotechnical information.  I will see if we can do some water sampling as well.  

Artisi: we would use a water agitation system around the float so that the water does not freeze in the pumps vacinity.  A believe tapping into the lake horizontally would be an easier solution.  We may use a float and anchor system for the end of the inlet pipe however to limit sediment intake.  In this senario we would allow the float to freeze.

Thanks again for all your comments and please feel free to give me any more input!
ornerynorsk (Industrial)
16 Jul 09 15:52
With constant flow, freeze-up should not be a concern in the well, nor should silt and small solids if you are using a trash pump, or other pump that is forgiving of particulate matter.  Your pump intake should be sufficiently above the lake bed to preclude most sand and other nasties, your flow velocity should tell you just how far this needs to be, as well as the approximate diameter vs open area of your well screening.

If you are in an area with severe winter, some of the flow can be tapped to provide aeration around the well to prevent it being destroyed or torn out of its position by the ice.
jte (Mechanical)
16 Jul 09 16:15

Quote (MikeHalloran):

The grid is needed to exclude humans and other trash.

Good one Mike! Having a good day? Everyone treating you kindly?

jt

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