# Dewatering



## dayexco (Mar 4, 2006)

I know we deal with different soil types. 

Locally, areas we have to dewater, we hired well drillers to place us wells, (typically 50 feet apart) with high capacity submersible pumps to lower the static water table. 

Sometimes depending on the water table, they had to be placed closer. We preferred this over sand points because it freed up that side of the excavation for the most part. 

On clay soils with water bearing sand lenses , we would over excavate 5-6 inches, use 3/4" rock back to grade for a french drain, stick a submersible in there to remove the water.

Worked well for us. 

How do you guys do it? 

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## rino1494 (Jan 31, 2006)

Typically dig a hole to the side deeper than our normal excavation. Place a vertical piece of 12" or larger HDPE in vertically with some holes drilled in it. Fill around with gravel and pump.


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## dayexco (Mar 4, 2006)

there are occasions we have to lower the water table 10-12'. 

in those areas, typically it's a very clean sand/gravel. you wouldn't be able to get a hole dug to place any pipe like you're talking. we've had situations where we were pumping 300-400 gpm per well.


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## mattg2448 (Jan 26, 2015)

I'm with rino, we use a vertical pipe with a submersible in it. As far as drilling sumps, never seen that around here.


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## Moxley-Kidwell (Jan 28, 2011)

We usually do as Rino explained close to home. 

FIL's old company worked close to Bethany Beach Delaware for a couple years, when they first started to do pond work they used well point dewatering. Bunch of "straws" for lack of a better word in the ground all tied to a large pipe and pump the entire perimeter. Worked great but was very $$$$! They installed everything and left about 20' hole for the equipment to move in and out of the ponds.


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## rino1494 (Jan 31, 2006)

dayexco said:


> there are occasions we have to lower the water table 10-12'.
> 
> in those areas, typically it's a very clean sand/gravel. you wouldn't be able to get a hole dug to place any pipe like you're talking. we've had situations where we were pumping 300-400 gpm per well.


I'm in the mountains, luckily I do not have to deal with well points.


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## JDavis21835 (Feb 27, 2009)

mattg2448 said:


> I'm with rino, we use a vertical pipe with a submersible in it. As far as drilling sumps, never seen that around here.


You get much farther west of you, and you will see it. Around the Flint and Clio area I've been around a few deep jobs that required dewatering. One was a trunk line sewer, the total depth was 50 feet. On that job Mersino drilled 8 inch wells in every 25 feet and dropped big submersibles to pump 24/7. 

In the Clio area there is a sand layer on top of clay, it has a lot of water in the area. Glavve did a sanitary main that was 20 feet deep on Vienna rd. They had a point dewatering system that was running constantly. They were pumping almost 500,000 gallons a day, and still were dealing with 2 feet of water in the bottom.


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## Bondo (Dec 7, 2007)

> I know we deal with different soil types.


Ayuh,.... 'round here in Jefferson County, We've got bedrock, or clay,....

The clay over burden can be from nothin' to 40',....

When openin' up a jobsite, such as an industrial park, deep ditchin' is how we can generally lower the water table of the area,....

This park, 'bout 100 acres was opened in the late '80s, has ditches 3' deep on the high side, which puts 'em on bedrock, to 'bout 20' deep at the low end, which isn't down to bedrock, but still dries out the upper layers,....

Last year, We did the ground work for a medical arts buildin',...
It was a swamp, several feet of over burden, then pitched bedrock,....

We stripped the over burden, 'n stacked it outa the way, then hammered trenches in the bedrock to drain the water around the site,....
Then regraded the site in crushed limestone up to near the original grade, with all the infrastructure in place, poured the foundation, built the buildin', paved the parkin' lot, 'n used the dried out overburden dirt for soils to build the lawns,...


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## mattg2448 (Jan 26, 2015)

On the mess of a job I'm doing now, I cut a 1/4 of the detention pond and cut ditches from across the whole site into the pond and have a 4 inch pump running non stop


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## Upchuck (Apr 7, 2009)

We use stand up pipe also. Luckily, we have had any jobs that required well points.


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## dayexco (Mar 4, 2006)

We have soils here that will give up several hundred gallons of water a minute with Wells spaced 50 feet apart. 

As I said earlier, without points or wells, you wouldn't get 5 feet in the ground. 

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## Metro M & L (Jun 3, 2009)

dayexco said:


> there are occasions we have to lower the water table 10-12'.
> 
> in those areas, typically it's a very clean sand/gravel. you wouldn't be able to get a hole dug to place any pipe like you're talking. we've had situations where we were pumping 300-400 gpm per well.


I think the technical term for that is a lake.


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## mattg2448 (Jan 26, 2015)

Metro M & L said:


> I think the technical term for that is a lake.


Haha


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## dayexco (Mar 4, 2006)

Here's a pic of my competitor's setup. Works great, but I don't like having both sides of my excavation tired up. 

Stringing pipe, swinging pipe over it, laborers stumbling over it. ..
Personally, I like wells. 

We can get at least a 40-50' spread between the wells which gives us a lot better access to the hole. 

Another thing, the driller would have these in place and pumping by the time we got there, and pulled their well casings after we were done.









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## Upchuck (Apr 7, 2009)

Seems like a pain to work around that


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## jhark123 (Aug 26, 2008)

Is there are submersible in each hole?


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## dayexco (Mar 4, 2006)

In the picture above? No those are all sand points hooked up by the red hoses to a 10" pump st the end of the 8" manifold there. 

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## Moxley-Kidwell (Jan 28, 2011)

That setup is the only "professional" dewatering that I've ever been around. Worked like a charm at or even below sea level about 4-5 miles from the atlantic. I can see it being a pia to work around though.

The only thing we did around it was drive equipment in and out of sediment ponds while dewatering, there was a good size gap for equipment with a bunch of the wells surrounding the entire perimeter. Amazing how much water they pull from the ground.


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## dayexco (Mar 4, 2006)

Yeah, each one of those points are good for 20-30 gpm

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