Water Drainage Design to be Pumped into a Rock Pit 1

[SolutionsnotProblems]

Hi,

Can someone let me know if having a sump pump to pump water into this rock pit is an okay design?

Any thoughts on this would be great.

Thanks,
TK

 

[miningman]

well even at 500% magnification , I cant even get a basic understanding of this design. I suspect you're not going to get much advice here

 

[Artisi]

Agree with miningman on drawing.
As for pumping into the pit, why not, provided the input doesn't exceed what can be discharged from the pit - - a complete unknown.....

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

What's a "rock pit" - Is this another name for a soakaway?

You need a nonreturn valve, but unless your pit is subject to a lot of water ingress I can't see an issue.

But then I can't really make anything out on the drawing...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SolutionsnotProblems]

Hi All,

Thanks for the comments. I've converted the photo to PDF attached -hopefully this helps.

The system consists of two 2HP sump pumps, a backflow preventer check valve (non-return valve, and the rock pit is buried. Unfortunately, the surrounding ground is mostly clay so it's not very permeable.

Another odd thing we found out when this was build is that there seems to be small drain rocks inside the piping....not sure how to explain this as there's a backflow preventer so there shouldn't be any back pressure.

TK

 

[Artisi]

"Unfortunately, the surrounding ground is mostly clay so it's not very permeable."

The info. regarding the pit, pumps and ancillaries is meaningless without knowing the uptake of the surrounding ground.

The answer to your question - is, "how long is my piece of string?"


It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[HTURKAK]

I suspect that, this is a valve chamber for water transport pipeline having dia. 40 in.

Acc. to the picture posted, my guessings and suggestions are;

- Delete the sump pump and rock pit..Just provide a hand pump to drain soakaway.. If the pump is for major leakage , the chamber will be flooded and the pump will not work..

- Delete the supply fan. The vent pipes will be enough for drying the condensation in the chamber..

 

[LittleInch]

This all looks like something that is massively over designed to me.

And it's all to measure flow part way along a pipeline? Why?

But if you want it....

Questions - Where is the water table?
what influx of water are you expecting?
Is the sump a square sump ( about 100litres of water) or a channel along one side ( about 500l of water)

So :
if a square sump means you pump would work for about 30 seconds then shut off. That's not very good.
Your rock pit (1m3) is full of "19mm clear crush". What sort of void fraction do you have there. if it's only 10% then you will fill the sump in one go.
If the channel is 500litres then it will sit there and go nowhere or bubble out of the ground.
If permeability is very poor then the sump isn't big enough. But you can measure this or test it. That's what they do for house soakaways for septic tanks etc
Have you not thought of using pre cast concrete segments with holes in it and backfill around with your 19mm stuff instead?

You have a fan in there?? Why? Never seen one like that, ever.

So I think someone has more money than sense, that's what I think. IMHO.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SolutionsnotProblems]

Hi All,

Thanks for the reply. The site in located in Delta, BC, Canada. It rains 2/3 of the time here. I've attached a photo of what it was like during construction, lot of water during the Spring, end of summer, fall, and up to mid winter.

Artisi - I hope my attachment help you some more. Alternatively, please let me know what you need so that you can answer properly.


The waterproof chamber was design to allow the user to get a flow rate reading off the 40in dia. pipe. The fan was put in for confined space entry safety requirement; instead of bring a portable fan, the user simply turns the switch at the kiosk. The sump pump system was design to remove any water that may have entered the chamber. The sump pumps have a built-in float sensor and kicks in when the water is higher than the sumps (about 12inches). There's a back up sump pump. There's also a float switch located higher than the sumps that tells the user to check the chamber as this means the sump pumps aren't working properly.

LittleInch
1. Originally there was no water table identified. During construction, it was identified that water was running underneath the 40in dia pipe because it was acting as a flow channel. As we start digging to construct the chamber, we essential created a pool for the water to localized (because the clay was impermeable)

2. For the Chamber, we have design and construct it to be waterproof. Not expecting to have any influx of water.

3. The sump pit is (0.6mx0.6m.0.5m) = 180 liters

Not sure about the void fraction but gravel is typically a void ratio of 0.4. I will take your suggestion for the pre-cast.

I am curious as to why we are getting the 19mm clear crush rocks inside our piping though. Is there back flow pressure because the pumps are over design and it's pushing the rocks inside the pipes?

Thanks,
TK

 

[mk3223]

First, why to risk the person to enter the U/G chamber? As only for the water flow measurement, can the chamber to be replaced with a covered sump with a sump pump, which may be lifted from the grade?

If the pumped water is to discharge to the rock pit and then flowing to the trench next to it, why need to have the rock pit?

Is the 19mm rock found in the pump discharge pipe, and from the rock pit? The pipe should be inspected after installed and add a perforated pipe cover at the open end for protection.

 

[miningman]

I'm inclined to agree with Littleinch in terms of this being grossly over engineered but having said that, if this is Delta BC, then that opens up a number of issues. Yes this is a wet part of the world and my immediate thoughts are this is a perpetual motion machine!! The location of the rock pit is only a few meters away from the sumps. Regardless of concrete walls, I forsee cracked concrete and water flowing to the pumps faster than they can pump it!! Are these drawings stamped by a P.Eng??? Is he aware of climatic and geological conditions of the Delta area??? Id be tempted to report the designer to the local engineering authority. Is this area of Delta part of the reclaimed land that Vancouver airport is built on??? The entire airport is likely to slide into the Pacific ocean during the next significant earthquake. And what exactly is the purpose of the 40 inch pipe?? seems like a gross mismatch compared to the 2HP pumps with 2 inch pipes?? If the sump has only 180 litre capacity , do you really think a 3 litre per second pump is an ideal match??? How often do you think the pump will cycle?? Hint, I think it will burn out within 12 months