Is it okay to add dirt to the top of a septic drainfield?

[Pushing_Tin]

I am wondering if it is okay to add dirt on the top of a septic drainfield. There are low areas in the field that can pond water during the rainy season and I'd like to fill these areas in. I know to keep heavy equipment off of the lines, but is there any other reason not to do that?

 

[beenthere]

That would depend on the drain field, the drain tile, the soil, the depth, and prolly several other things.
Standing water on a drain field intuitively sounds like a bad thing. Draining the water away from the field seems like a good idea.

 

[clemsonfor]

My only thought is that it would interfere with the suns heat from evaporating some of the moisture? Water standing sounds like a normal if you have received a lot of rain. After all water comes out of your tank and its coming out of the sky.

 

[poncho62]

I wouldnt see a problem filling in those low spots....the waste disperses downwards once it leaves the system...you dont want it coming to the surface....The concern I would have is what equipment you are going to use.....Is it to heavy and would damage the tank or runners.

 

[Pushing_Tin]

I wouldnt see a problem filling in those low spots....the waste disperses downwards once it leaves the system...you dont want it coming to the surface....The concern I would have is what equipment you are going to use.....Is it to heavy and would damage the tank or runners.

I would use my 2320 once it dries out enough.

 

[beenthere]

Do you know how the drainfield is constructed?

Mine is 3' down in sand. I have no restrictions on driving over it. In fact, have my firewood stacked between the three runs (see pic). This drain field is 200' from the septic tank.

Some around here have to have what is called a "mound" system (their land won't perk), and the drainfield is constructed above ground in a mound. Their recommendations is no equipment on them.

 

[Mousefield]

Do you know how the drainfield is constructed?

Mine is 3' down in sand. I have no restrictions on driving over it. In fact, have my firewood stacked between the three runs (see pic). This drain field is 200' from the septic tank.

Some around here have to have what is called a "mound" system (their land won't perk), and the drainfield is constructed above ground in a mound. Their recommendations is no equipment on them.

It's called a pressure system up our way, it is what I have. Pumps up into the field. Special sand about 3ft above the rest of the ground. Had to put it in due to regulations, clay ground plus close to the creek. Cost lots of $.
I do use my ride on lawn tractor to mow it but nothing heavier as it would probably cush the field. Was told not to drive on it with anything heavy or to let trees grow on it.

 

[CurlyDave]

My belief is that the septic drain field must be aerobic, i.e., enough oxygen from the air for oxygen breathing bacteria to work on the waste.

The tank itself is anerobic, and contains a different type of bacteria.

If you add very much dirt you will suffocate the aerobic bacteria in the soil at the level of the discharge pipes and may screw things up.

 

[General Lee]

Drain fields are usually ok to drive over with avergae equipment such as vehicles, tractors, etc. I'd be nervous having something as heavy as a concrete truck drive over them. Now your tank is a different story. I wouldn't put anything other than a riding mower or compact tractor over it.

 

[VABlue]

I suspect your field looks similar to mine - some small sags over the lines where the dirt has settled in. If so, you shouldn't need more than 6-12" of dirt, right? That should be fine, and your 2320 with a scoop of dirt shouldn't hurt anything. I run my 2305 over my drain field with a full bucket of dirt and the weight box on the back end - no worries...

 

[Pushing_Tin]

I suspect your field looks similar to mine - some small sags over the lines where the dirt has settled in. If so, you shouldn't need more than 6-12" of dirt, right? That should be fine, and your 2320 with a scoop of dirt shouldn't hurt anything. I run my 2305 over my drain field with a full bucket of dirt and the weight box on the back end - no worries...

Yeah 6" would be the most I would need. Probably 10 buckets worth would be enough.

 

[Highbeam]

Since this is an engineered mound system and built entirely of sand, I would use the same sand to "level" the surface. You want the water to shed and for oxygen to get into the aerobic bacteria. CurlyDave has the basics spot on. You would need to add a nasty layer of tight soil like clay to prevent air from making it through the soil though.

 

[magicheater]

My belief is that the septic drain field must be aerobic, i.e., enough oxygen from the air for oxygen breathing bacteria to work on the waste.
The tank itself is anerobic, and contains a different type of bacteria.
If you add very much dirt you will suffocate the aerobic bacteria in the soil at the level of the discharge pipes and may screw things up.

How can another 6" or less of dirt suffocate the aerobic bacteria? The dirt has settled from the original level. I have the same thing happening on my fields but am more concerned about the plastic tunnels that were installed being collapsed, more than anything else. Hard to tell unless you dig them up. This is a recently new technology, last 20 years or so. Old technology was perforated drain tile over washed stone. You can definitely see the line where the tunnels were laid.... any thoughts?

 

[Pushing_Tin]

In the dry months what would be the max weight you'd drive over the drain field?

 

[RadarTech]

good thread folks..

I was considering the same thing!
My drain field is lower than the house basement and in some cases it has washed.. Losts of weeds and broken tree limbs as it is too much of an angle to do anything but foot patrol...
This is a summer/fall project..

I think I want to plan grass down there and clean it up....

I appreaciate the thoughts...


J

 

[CurlyDave]

How can another 6" or less of dirt suffocate the aerobic bacteria? The dirt has settled from the original level...

According to this article Article: Utilizing Soil Tests the aerobic zone of soil is the top 6 or 7 inches. You don't have to read all of the article, the depth of the aerobic zone is in the first sentence.

If you add even a few inches you can easily take your septic field from aerobic to anaerobic.

 

[Ford850]

If you add 6" of soil in the settled areas, wouldn't that become the top 6" and be aerobic? If it's a standard drain field, do you want the liquid to be perculating to the top 6" anyway? I thought it was supposed to be soaking into the soil beneath the bed.

 

[Highbeam]

The waste water is supposed to go down into the soil below. Correct. As the water exits the drain pipe and soaks into the earth the soil becomes dry again when air is allowed to fill the voids. That air comes from above. That air has oxygen to feed the aerobic bugs. If you added a layer of clay or plastic then you wouldn't get oxygen and the field would lose the aerobic bugs to be replaced by anaerobic bugs that don't need oxygen but love the waste. Anaerobic bugs eat much slower and won't be able to keep up so the funk will grow and plug up that receiving soil below. This will eventually cause surfacing waste water or a backup into the house.

If you add good inorganic soil like sand then you can safely add feet of fill over the drainfield. I have been quoted that 2 feet of soil cover is safe so long as it is good sandy soil with no organics. The kind of soil that water freely flows through. Color will be grey or tan and won't ball up when you get it wet.

 

[Willl]

Since this is an engineered mound system

Huh ?

 

[Ford850]

The waste water is supposed to go down into the soil below. Correct. As the water exits the drain pipe and soaks into the earth the soil becomes dry again when air is allowed to fill the voids. That air comes from above. That air has oxygen to feed the aerobic bugs. If you added a layer of clay or plastic then you wouldn't get oxygen and the field would lose the aerobic bugs to be replaced by anaerobic bugs that don't need oxygen but love the waste. Anaerobic bugs eat much slower and won't be able to keep up so the funk will grow and plug up that receiving soil below. This will eventually cause surfacing waste water or a backup into the house.

If you add good inorganic soil like sand then you can safely add feet of fill over the drainfield. I have been quoted that 2 feet of soil cover is safe so long as it is good sandy soil with no organics. The kind of soil that water freely flows through. Color will be grey or tan and won't ball up when you get it wet.

It sounds like you are talking about a mound system. I thought the OP had a traditional drain field.