Intake Design 2

[jvoisin]

I am looking for some input on how to size a water intake.

It is for a smaller distribution system. Phase 1 max day is 882m3/day and ultimate is 3628.8m3/day. The intake has to be HDPE, and I think it will be in the 300mm diameter range.
Also, are there manufacturers in Ontario that supply pre-cast pipe anchors for sinking?

Thanks
Joe

 

[bimr]

You don't provide much information. Is it a river? lake? Municipal?

A common method to install intakes is to install the intake pipe with a directional drill out to the intake location. Then you come up to the surface and install a well screen intake.

A riverbank filtration intake may also be an attractive option.

http://publications.usace.army.mil/publications/eng-manuals/EM_1110-3-161/c-4.pdf

The water flow velocity objective in the intake pipe should be to achieve an approximate velocity minimum of 0.9 m/s to a maximum of 1.2 m/s (3-4 ft/sec). The minimum flow is to prevent the deposition of solids.

https://www.google.com/webhp?hl=en&...540,d.b2U&fp=2c2bbb2c7dbbb4cd&biw=942&bih=431

 

[QualityTime]

I beleieve the Keswick Water Treatment Plant in Keswick Ontario had a HDPE pipe and they used concrete anchors to wiegh down the pipe. Did you try to ask your HDPE pipe manufacturer for a design of the concrete anchor? They should have one and they will tell you how to space them

 

[bimr]

Pipeline weights:

http://www.armtec.com/en-ca/products-and-services.aspx

 

[jvoisin]

Bimr,

The intake is into a lake, about 250m. We will require the first 100m or so to be dredged or directional drilled to obtain sufficient cover over the intake since it is shallow before the water drops off.

If you directional drill, how can you ensure the pipe wont float in the future? I expect you cannot install concrete pipe anchors on the portion of pipe that is directionally drilled?

 

[cvg]

flood the pipe then ballast. If the pipe is full of water, it will not float.
ACB mattress is often used.

 

[bimr]

I was thinking that you would directionally drill the entire pipe length out to the intake.

 

[hydrae]

cvg, I beg to differ, HDPE has a density of .97 to .93g/cm3 so it will float
although 'just' floating when full of water

 

[cvg]

Specific Gravity 1.68 ASTM D792

dont belive everything you see on wikipedia

 

[bimr]

Most expect HDPE to have a lower specific gravity. CVG, what is your reference?

Q: Will HDPE pipe float in water?

A: Yes, HDPE pipe has a specific gravity of about 0.95, so it will float. For underwater anchored pipeline installation, it is important to specify the proper weights and spacing of the weights. Screw-anchors are a practical alternative. Whenever possible, an underwater pipeline should be installed in a trench with protective crushed rock cover.

http://iusco.com/FAQs

 

[IRstuff]

http://www.sdplastics.com/polyeth.html

http://www.dynalabcorp.com/technical_info_hd_polyethylene.asp

http://www.maropolymeronline.com/Properties/HDPE Prop.asp

All list HDPE around 0.95, including the last one, which also references ASTM D792

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[hydrae]

An my reference was taking a piece of HDPE and placing it in water,
guess what, it floated

 

[equimo]

The 300 mm is ok, however 8" gives 1.23 m/sec velocity which is aceptable.
The water intake in a lake shall be type floating supported by a floating pontoon with a screen basket for the intake. This is to have the intake always under the surface level but far from the lake bottom where sediments will clog the pipe.
Drilling is ok if having a gravity pipe to the storage/treatment tank.But having a pump you do not need to drill. In case the water drops down bellow the dam level and you discharge is still bellow the water level, a vaccum pump is good idea: it works a siphon.

 

[stanier]

You dont need afloating pontoon. Aslong asthe inlet is kept aove the mud level there is no need. The useof a "mussel" on the intake allows for very low approach velocity andthus themud will not be etrained. h "mussel" is used to get intake from very low water levels.

http://www.irrigationwarehouse.com.au/category304_1.htm

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[bimr]

The poster says he is from Ontario Canada. One would have to assume that the lake is ice covered at least part of the time. How would the floating pontoons or mussels work on an ice covered lake? Don't really think they are an option.

 

[stanier]

Mussels are below the water and ice. Pipe is on the bottom of the lake and upturns to an inverted mussel above the mud line. Even if the PE line were allowed to float the pipe would turn down below the ice to the mussel.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[jvoisin]

I also have another problem.

At the shoreline, I only have about 3 feet of depth from the water surface to bedrock. Has anyone ever installed a shallow raw water intake. My fear is it getting hit by boat traffic and of course freezing.

Any thoughts?

 

[dicksewerrat]

When in doubt, call the blasters. And it is fun to watch. You can have them blast you a trench till you get to a grade you like.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[bimr]

Is the water elevation in the lake at a constant height?

What about a riverbank filtration system?

 

[QualityTime]

If anyone has ever designed an intake pipe for a water plant from a lake or river and studied the hydraulics what the water level would be in the low lift wet well at maximum plant flow you would know right away that you have to cut into the bedrock. There is something wrong with your thinking, the wetwell design or how you are doing your hydraulic calculations if you think that you can get away with leaving the pipe close to the surface of the lake bed near the shoreline.

From a pipe protection point of view definetly the pipe should be trenched into the bedrock

I think you need more senior help.