# septic drainfield setteling



## kubotaman333 (Feb 26, 2006)

When repairing an exsiting drainfield in established yard by adding additional lines or alternating drain field how do you guys deal with the settling of the lines. Do you go ahead and seed and straw before you leave and then return with soil to fill voids, or just rough backfill and comeback in two or three weeks to finish grade and seed?


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## tgeb (Feb 9, 2006)

You're joking ....right?:blink: 

I have never, never gone back or been called back on a septic install due to settling.

I compact the crap out of the trenches when back-filling. Then final grade and seed and put down straw, I also will haul away any excess soil that would have been displaced by the excavation and the stone fill. (if required).

I will know when I first look at the job if hauling will be required and simply make that part of my price quote. 
Most guys don't include this and that is why I do few septics. My price is higher. 
The "other guys" just dig and cover and when done the home owner is left w/a big mess. :no: 
But they saved a few bucks by going with the "other guy". :laughing:

It takes very little time to do the job right and little money to rent a tamper. Take care of the settling problem while back-filling and you have no settling problem...simple.

PS. Welcome to the site Kubotaman.


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## jmic (Dec 10, 2005)

Tom,
Are you saying that you compact the trenches with a compactor? :blink:


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## kubotaman333 (Feb 26, 2006)

Tom,

The health dept. would go crazey if they saw me compacting a drainfield. I usually use infiltrator for drainfield and it does not allow for compaction. thanks for the help.


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## rino1494 (Jan 31, 2006)

Well, we don't get involved with repairs, we just do new construction. So we just rough grade with no compaction. Besides, we have in our contracts that we are not responsible for settling.


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## fhdesign (Jan 17, 2007)

If properly backfilled there should be little to no settlement, but to answer you're question, I would finish grade, seed and straw. After the grass starts to grow I would then repair anything if needed.


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## denick (Feb 13, 2006)

Kub man,

If you are referring to a standard leaching field trench 3' wide. Filled with stone and covered by filter fabric and up to 12" of topsoil? There is minimal settling like the same trench just backfilled with dirt. The stone unless violently vibrated doesn't have a settling factor and the fabric covering the stone keeps the topsoil from filtering down into the stone. The fabric also distributes the weight of the backfill equipment when grading the topsoil cutting down on ununifom or over compaction. All that contributes to very little settling.


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## kubotaman333 (Feb 26, 2006)

Denick,

Around here everybody just backfills infiltrators with dirt. This seems to be fine with our health dept. Are stone and fabric required there or extra that you use.

Thanks for the help,just trying to get some advice.


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## tgeb (Feb 9, 2006)

My apologies, kubotaman.  

I forget that we all are in different areas and that the rules change from jurisdiction to jurisdiction.

Here we do deep systems, typically between 5 and 9 feet deep, then we are required to place in the trench a specific amount of stone usually between 3 and 6 feet of washed 3/4" or 2" stone and also bed leech pipe in the top 6" of stone, then cover with filter fabric.

In these circumstances we would normally be back-filling 2 to 3 feet of soil in the trench.

What I usually do is fill the trench loosely and then run the backhoe back and forth a couple dozen times then fill more and repeat.

I will sometimes hit the ends, corners, and crossovers with a jumping jack tamper. 

As Denick stated this type system cannot be harmed by compaction as the infiltration system is within the confines of the stone bedding. 
If not compacted....well in a few months you can find the trenches plain as day. These low areas will also help kill the system as then rain fall and runoff gets directed into the trench.
Some of the installers here just cover, get paid and run, leaving the homeowner with a mess a short time later. I don't like that method...when I am done with it, it's done. 

I don't know that a shallow system of the kind you have described has ever been done around here. I would be interested in hearing more about them though. 

Where are you located anyway?


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## denick (Feb 13, 2006)

Wow, here it is again, How different things are for many of us. 
tgeb's system is possibly never done here. jmic does many more system's than I do a year in CT and would know better over a wider area of the state. I don't think you will find any in our upper corner of the state.


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## kubotaman333 (Feb 26, 2006)

Tom,

I'm in Morgantown WV its about an hour south of pittsburgh. Most of the drainfields I do are trenches 3 feet wide with infiltrators laying right on the ground. The bottom of the trench is level and no more than 36 inches deep and at least 18 inches deep. we do use low pressure pipe systems,eljen systems, and direct discharge HAU but infiltrators are the most common.

p.s. no apologie needed,thanks for input.


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## rino1494 (Jan 31, 2006)

99% of our septic systems are elevated sand mounds. 1% of the time, we will do a convential system, which is the same thing as a sand mound, without the sand. It is a square bed that we dig out and place 2ft of 2B stone, place the pipes in a grid and cover with 6" of 2B and filter cloth and cover with 12" of dirt. Minimum size of the beds are 600 sq ft.


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## jmic (Dec 10, 2005)

Ok, in the time I've had my septic license 18 yrs. or so I've done probably (2) systems around 5' deep because at that depth we ran into a nice layer of bank run gravel which perced much better than the soils above it and in this area ground water was not an issue.
That being said for the most part between trying to be 4' above ledge, and 18" above the water table ( or what they call motteling ) layered rust color in the soil that shows sign of seasonal high ground water with the bottom of your leaching trench I usually always either work with lowboys ( 12" high x 4' wide x 8' long precast concrete gallies) or a 12" deep by 4' wide trench with 1 1/4" washed stone w/ 4" perforated pipe. With the stone trench it typically calls for from the bottom 6" of stone, then the pipe and then more stone so you are 2" above the pipe with the stone , so you have a total of 12" of stone. Then roll out the filter fabric and cover with 6" of material. What determines if we need any septic sand for the system is: 1) Perc Rate, 2) Min. distance to motteling or ledge. 
Also sometimes if the site has say more than 6" of topsoil and you have to keep your system high you may have to remove the topsoil and replace it with septic sand and then when finished cover the whole area with the top soil.
In using the stone / pipe trenches this will give us 3 sq. ft. of leaching area per lin. ft. of trench.
In using the lowboys in the size I mentioned above we can obtain 5.8 sq. ft. leaching area / lin. ft. of trench. ( Used more for a confined area of suitable septic area and also to place under driveways or parking areas by using H-20 series, which are made heavier duty)
I'm about ready once the snow melts to start a system I've yet to do which will give you 11 sq. ft. of leaching area per. lin. ft. of trench, I'll be sure to take some pics. of this installation.
I will also add in Conn. for new const. you need to provide ample room on a site for a 100% reserve area, although you do not have to install it . 
I could keep going on about systems, but this has to be the longest post I've done on here and I don't want to start a bad habit.:laughing:


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