Build workshop over leach field: stupid?

[BooRadley]

Want to build a workshop, something like 30'x40', two stories. Bottom is workshop, top floor is apartment. One available area for building is an area where there is a leach field. The septic tank attached to the leach field will be pumped out and destroyed 30 days before construction begins.

There are a couple of things that make building in this area a more attractive option than building elsewhere on the property. Question is, is it a bad idea because of the leach field?

 

[akdiesel]

If the leach field is not going to be in service I don't see any problems as long as the ground area is prepared like any other location.

 

[Sick Puppy]

Being someone not in the US, what is a leach field?

 

[Garage5.9]

water leaches from the septic tank in to a field of pipes

 

[Kevin54]

If the leach field is not going to be in service I don't see any problems as long as the ground area is prepared like any other location.

I wouldn't see a problem either all except I would make sure you have a good vapor barrier down. I imagine over the course of the years past that many have built over abandoned leach fields and maybe never known it. The only reason I say about the vapor barrier is that for years your liquids have been leaching into that area. Between laundry soaps, shower soaps, years of toilet water, and whatever else liquid may have been dumped in and leached into the ground, I would want a little insurance against something brewing and coming up. Similar to radon gas in basements. So a vapor barrier should control that.

The main downside I see that you will have three fingers underneath your slab for the leach field, that creates a very remote possibility that the tiles could collapse from any weight and crack your concrete floor. You will have to dig out any sod to prep for a floor. If per chance you don't hit the fingers (tile) you are at least closer to them, increasing the chance.

 

[eldirector]

How deep are the tiles? I remember my parents adding on to the house, and the leach field was not all that deep. It is entirely possible that you will be digging out the tiles when you dig out for footers and maybe even your floor. Heck, if you are going to dig down close to them, you may as well dig them out and back-fill.

As mentioned above, a good vapor barrier and build away. Its just well-fertilized dirt!

 

[NUTTSGT]

Why is the septic tank being destroyed ? Are you connecting to a sanitary sewer ?

 

[larry_g]

I would think that you would be ok but there are so many variables that without knowing all I would not go with suggestions here based on the information you have given.

How long has the leach field been dry?
what soil conditions do you have?
how deep is the piping?
How long has the field been there? Has the soil had time to compact over it?
Do you plan to remove the piping?
What style of foundation are you using?
You say you are pumping out a leach field? How was this 'field' constructed?

To many unanswered questions here to make a call on this.

lg
no neat sig line

 

[BooRadley]

Thanks all for your replies.


From LarryG:
How long has the leach field been dry?
The septic tank will be pumped out and destroyed 30 days prior to construction. It will be in use until the day the tank is pumped out and destroyed.
what soil conditions do you have?
Red clay mostly, through I do believe that the person who dug the leach field dug out the clay directly where each line would go and put in sand or similar earth.
how deep is the piping?
I am sure that the person who dug the septic and lines did a cheap, crappy job. Probably, they are not as deep as they should be.
How long has the field been there?
At least 22 years.
Has the soil had time to compact over it?
I guess.
Do you plan to remove the piping?
Well, I didn't originally, but if it is wise and not too expensive, maybe I should.
What style of foundation are you using?
Rebar reinforced slab, with footers.
You say you are pumping out a leach field?
No, just pumping out the septic tank.
How was this 'field' constructed?
In the conventional manner for a trailer house in the woods, where permits are not required. I have no clue what manner that is, though.

I would add to all this that there are trees growing all over the leach field area, and that there was one place where for years some of the septic water would come up through the earth. It doesn't usually anymore, but perhaps the earth is just saturated. The trees will be cleared away 30 days after the septic tank is pumped out and destroyed, regardless of whether I build there or not. I figure 30 days, and they will drink up some of the septic water, at least.

I appreciate all input.

 

[Sick Puppy]

Sounds like a ****** job, pun semi-intended.

If there is any chance that the underground piping can affect the land underneath or around your proposed garage, I'd rip up as much of it as possible. Don't know how this would affect your budget though...

 

[Adrien]

If you have a lot of trees in the area, not only do they need to be cleared out but all of their roots do, as well. I would suggest digging down as much as is needed to remove the leach lines as well as all organic material and building back up.

Adrien

 

[VHF]

Use the existing laterals as French drains!