Trench/ditch digging

I would like to dig a trench/ditch 10 feet deep, 5-10 feet wide, 35-50 feet long. The space between the neighbor's fence and my air conditioner is as little as 6 feet wide, so there is a limit to the space available to store dug-up dirt.
So, my questions are:
1. What kind of equipment should I get? Backhoe, trencher? Bucket width if backhoe? Since my width is as little as 6 feet, I can't have too much dug-up dirt to deal with. I understand trenchers only go down about 30 inches and have wheels 5-6 feet wide, so does the dug-up dirt go outside that width? Should I rent the equipment or engage a contractor to run the equipment?
2. Any idea of the cost? I'm hoping for a few hundred dollars tops.
Here's what I'm doing, if you care to know: The terrain slopes toward our house. The house has had water problems for years. Water has swirled through the crawlspace and it looks like some of the supports have been replaced and some rotted crossbeams have been replaced. The crawlspace has been enclosed with concrete blocks, obviously after some of these other problems have been fixed. I found that they were not properly waterproofed and had holes caused by huge roots from a neighbor's tree, which seem to have been undetected because they were hidden behind the gas meter and some enormous azalea bushes. I dug around the outside to a foot or two below the concrete blocks, waterproofing with stucco paint (stretches to 6X) and a 6-mil vinyl liner. So far, all this seems to have completely eliminated moisture in the crawlspace.
However, in working on the back corner of the foundation at the end of the waterproofing project, I dug to 2 feet and got some moisture. Dug to 4 feet and I had a pond. The top of the water would still only come to 2 feet below the surface. No matter how furiously I tried to empty the water, it would maintain that level at 2 feet below the surface. Once it began to seep, it continually increased in flow rate. Downhill, the soil under the deck was always wet; I never knew why until now. And the door below the deck began rubbing on the deck above it recently, so the deck is sinking. I dug four-foot holes at various places uphill from the original point of discovery and found that the water level is always 2 feet below the surface. Understand that I don't know how deep this water table is. But I think the house will be fine if I can keep any groundwater/water table at least a couple of feet below the foundation.
So, my plan is to dig this trench 10 feet deep. Since I expect the trench is going to fill up with water to 2 feet below the surface, I would attach metal fence posts to 10 foot wide 6 mil vinly sheeting to weigh it down and pull it to the bottom of the water-filled trench. Now, I have this vinyl going to the bottom of the trench; but the seeping water might build up at the vinyl sheeting and try to find its way around it. To prevent this, I would attach a 4-inch slotted pipe with sock (as used in french drains) at about 5 feet down the 10-foot sheet to carry the built-up water downhill to a leech field. I would staple the top of the 10-foot sheet to old wood that would hold the sheet up while I filled in the trench. If I have to use a trencher (and thus gamble that the 30-inch cut will be enough to carry the groundwater away), I would modify the size of the sheeting and the placement of the pipe. I don't see any point in hauling stone in for the trench; the ground is quite pourous and the stone thing would introduce a whole new world of installation problems. Anyway, with a few days' work, I think I can satisfactorily control the problem.
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Andy replies:
If I were you, I would hire a registered engineer to evaluate your problem. You may NOT be able to do this without injuring your neighbor's property, either thru excavation and possible cave-in, or water drainage damage. And be assured that if you do something to YOUR OWN property that damages YOUR NEIGHBOR'S property, you will have bigger problems to solve.....
Also, a registerd engineer can tell you where all this extra water is supposed to go to. It may not be allowed to drain the local water table into the local sewer system, or into the street, or into the neighbor's yard....
Get over the idea that you can do anything you want to your property. There are both civil and criminal laws which prevent your actions if they cause damage to anyone else....
Andy in Eureka, Texa
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If I ever had any intention of hiring a "registered engineer" to do this project, I wouldn't have posted my question on alt.home.repair.
John

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The whole point in the suggestion to hire a registered engineer is that if you have to be asking these questions on Usenet, you're not qualified to evaluate the potential for damage yourself.

--
Regards,
Doug Miller (alphageek at milmac dot com)
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I'm with you John on the whole hiring of the Engineer. That sounds very expensive. But it is a very valid point. You don't want to get fined for dumping into the sewer or anything like that, and you probably don't want your neighbour to take you to court for damaging their property. I think the solution would be to do the work yourself, but do some research (like talking to a building inspector, land scaper, etc) in your area to see how they would solve the problem and what the options are. That way you would keep the costs down, only use up a little of your time, and protect yourself. As for diggind the trech itself, what about one of those mini excavators? They're not too wide (but I'm not sure on the width) and should be able to dig down 10 feet. Your plan sounds good to me but I'm no expert (and maybe that's why it sounds good).
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Several problems with your idea.
A ten foot deep trench is unsafe, many people have been killed with cave-ins, it will have to be shored. If you dig next to a fence, the fence will fall in carrying some of your neighbor's yard, digging this deep next to your house will cause the foundation to collapse unless it is deeper than the hole you dig, which is doubtful. All that water will soften the edges adding to the cave-in problem.
A leach field will not handle all the water that you are talking about, you will need to drain to a watercourse that can handle it.

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When I use the term "trench" I am simply looking for a cut in the dirt to lower the vinyl sheeting into. No one will be going in the trench. I really had a narrow cut in mind, but I understand there may be problems working with a narrow backhoe bucket that deep. Also, I know the trench will be half filled with water. For that reason, the trench will be filled immediately, especially if I can come up with the best way to dig a narrow trench.
As to the effect on others' property, I have already covered that with the inspectors. Downhill from my lot is a creek. The inspector said there would never be a house there. However, I am well aware that I can't have a drop go on to this property.
Other unmentioned items include the fact that the neighbor's sewage goes through a clay pipe across the "trench" location, then under my house on the way to the street. It's really the city's problem, but the only way they can fix it is to run a pipe through still another's property, though it would not be under our house. It gets more interesting as we go, but the bottom line is that the city will help me out as long as they don't have to run the sewage pipe through another's property. I will be talking to them about an alternative to the leach field.
I'm not worried about the neighbor's fence falling in the ditch. I've already dug two holes five feet deep AT the fence. It is a stable situation. Two other digs confirmed the soil condition and the extend of the water table.
At this time, it seems more likely that I will have to use a trencher and will thus only have a 30-inch cut. I'm not too sure if I can keep the water away from my house with this shallow cut.
John

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says...

You should be able to rent a larger trencher. The one I used made an 8" cut to 48" depth. They are only about 4 feet wide, and place the dirt neatly along one side as they go.
-- Dennis
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I am sometimes too blunt, so please don't take this the wrong way. I think what the other posters are saying is that for an inexperienced backhoe operater to work on the deep trench when you have saturated ground may be a bit dangerous. Sorry to just blurt it out like that, but I think they were saying that for your own good. Even experienced operators have been known to land in the hole, on occasion.
If it is surface water, and not some huge spring under your house/yard, 4 feet or so should work fine. I think that most people also feel that a trencher is safer because the cut is narrower. If, hypothetically, you are digging and a dog goes in the ditch, you can't get it out without endangering a person in such a narrow/deep cut. On a commercial site, you would put a steel slip form into the trench to keep workers safe.
If you are going to do this, try a trencher. Also, forget about the plastic. Fill the ditch with crushed stone. That'll keep the water moving and will be zero maintenance. Granted, it may eventually fill in, but you won't own the house be then. But, put some landscaping cloth on top to keep the topsoil from going into it. This would be a simple and safe way to do it.
If you have clay soil, just go to the level of the clay.
If you start from downhill side and work up, it shouldn't fill up with water -- but you will get more sediment running out and you should control that (put in a bale a hay to slow the run-off.).
As for the sewer pipe. In all likelihood, you will break it. Almost anyone would. So go to your local builder supply store and ask how to fix it. Then get what you need before you start. You can always return it.
If it were I, I would also rent a big-ol snake and snake out the line since you have it open. Then it will be good and clear and won't cause you any trouble in the future. After all, it goes under YOUR house.
I did trenches on both sides of my house and across the back about 3 years ago. But I didn't have to go too deep. I hired a couple of local kids who were on the football team and had them dig it by hand. Let's just say, by the time they were done, they would looking forward to football practice and conditioning because it was so much easier! (The kids bulked up pretty good and had a great football season)
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I did a DIY water project once to avoid the intrusive building inspection dept.
......................................BIG MISTAKE the contractor I hired only installed the corrugated drain pipe on TOP of the footer, and didnt backfill to my specs, which were all gravel where a sidewalk was being replaced.... so the new sidewalk wouldnt crack
I fired the original contractor and ended up paying for the same job twice:( contractor 2 noted the pipe on top of the footer, it should of been a little below it so underground water wouldnt percolate up thru the basement floor. well I was out of $ so left it as is, he only redid part of the job.
that fall the basementy flooded again and I was forced to spend 6 grand on interior french drain.
If I had used the building inspector I might have paid a bit more for the initial job but would oif saved contractor 2 and 3 who did the interior waterproffing...
lessons learned with a big job those rules are there for a reason.....
on this fellows house, if he is only trying to keep a crawl space dry why dig down 10 feet deep, a couple feet may be all thats necessary....
a 10 foot deep execvation close to the property line may well cause settling or collapse of his neighbors property, house, driveway, sidewalks may sink settle and crack. $ liability for repairs
probably better to surround crawl space with a 3 foot deep trench with drainpipe on bottom landscape cloth to prevent pipe clogging and backfilled with mostly gravel landscape cloth over top covered by a foot of topsoil, having one or two leads going under home to redirect any water pooling under home, cover crawlspace with 10 mil overlaped poly sealed with tape, provide lots of vents under home so moisture cant accumulate
the goal is not have water under home, what happens 5 or 10 feet down really doesnt matter, in many areas thats the water table.
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The fence isn't the concern as much as the house(s).
First off, what kind of fence is it? Will the neighbor let you take it down?
Second, why so deep? Why not 4-5 feet?
How far away are the houses? Yours must be within 6 or 7 feet or where you will be working. Do you have a basement? How deep are your footers?
Can you go around the other side of your house to keep away from your neighbor?
What kind of soil do you have?
Where will the water go? Is it legal? Do you care?
That said, where I live, we have lots of water. We have about 2 feet of crappy soil over pure clay. So for me, there would be no use in going down over 2 feet -- just to hit the clay line. Going down 10 feet seems awfully deep.
At 10 feet, you have to worry about collapses. If the trench goes, will it effect your house (or your neighbors)?
Do you have a septic tank? If so, don't send water towards your leachfield.
Also, if you start on the bottom and work uphill, it might help contol your water during excavation. And don't forget some hay bales or plastic to control erosion and sediment.
In all likelihood, you will need a backhoe with an extendable arm so you can reach past your A/C and not have to be right next to it.
Good luck. If you give some more info, someone might be able to help more.
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John <John@ wrote:

First off, and this is just my opinion, what you are describing is *exceedingly* dangerous. You have not mentioned any safety measures, such as fencing to keep people and animals from falling in and killing themselves. This would not be a one-day job, so it would be open over several nights (at least).
Second, you can't just dig 10 feet down and expect to survive while installing pipe at the bottom. A proper trench has to be 'cut back' to provide a measure of safety for people working at the bottom.
Your trench: a 'cut back' trench: | | \\ / | | | | -- --
There's no such thing as a 'safe' trench, only deadly trenches and deadlier ones. I worked for my local telco, and trench safety was *mandatory*.
Third, consider the structural aspect of your plan; your house was built based on solid ground being in that location. If you remove that much ground (even temporarily), will there be structural movement or stress load on your foundation?
Fourth, the water seepage is a *huge* complicating factor! Plastic or no, you won't get the walls of any trench to last if there's any significant inflow, and it sounds like there is. Key word: "mudslide"
If you don't have a Civil Engineer for an in-law, have a few Contractors come over to review the situation and give no-obligation estimates. One of them may see a solution or know of a product that will help.
There are more pleasant ways to die than suffocating at the bottom of a collapsed trench.

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How about trenchless boring? They can do amazing things with those devices these days, I see a whole lot less trenching than I used to. Only a hole at each end.
Look for a contractor in your area.
Pulling a drain tile would seem to be a quite doable task, and a lot less mess than digging.
I don't think you need to go down to that depth. Is the water surface water (aka rain) or sub-terrain (like a spring)? At some point, your going to being trying to drain the water table, which may not be a good thing.
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Based on your description of the problem, your would have to be crazy to expect your solution to work.
1) 6mil plastic won't do anything for you. Over time, it will develop holes and tears. This is unavoidable. Water will go under, around, and through it.
2) trying to lower a water table is not a simple matter of draining into a leach field. You are talking about millions of gallons of water. You need to figure out what flow rate will be needed to lower the table an adequate amount. What you have described (porous soil, rapid seeping, very high water table) sounds like you would basically be tring to drain an underground river with a few plastic sheets and some 4-inch pipes.
3) you described your "trench" as 5 feet wide and 10 feet deep, filled 8 feet deep with water. That is just plain crazy, and dangerous, and undoable for "a few hundred dollars" in a "few days". That close to your house, your foundation would crumble, the fence would fall in, the neighbor kid and the mailman would fall in, drown, then sue you, your backhoe would fall in and you'd go bankrupt, loose your house, not to mention being dead. All unpleasant things.
4) Can I say again that this plan is crazy. You can't dig a trench in 8 feet of water. You didn't even mention pumping during construction.
5) Lowering the water table may cause cave-ins and sink holes, perhaps under your house, under the street, under your neighbors house. Google Images for "water table sink hole" to find some really amazing photos of what can happen when water tables drop significantly. Locally, I have seen sinkholes form after water mitigation was done wrong.
Since you don't seem likely to hire anyone to fix this problem, you are going to have to go back to the drawing board. But before you start thinking up plans and fixes, you really need to do some more research.
Try to figure out where the water is coming from, how much there is, etc. Is it seasonal? Is it fed by surface water, a spring, etc? Do your neighbors have water problems? Where will all the water go?
Just to give you some ideas for alternatives that might be more appropriate (depending on what your research turns up): - A sump-pump or three might be all you need, either under your house, or near the house, to lower the table just a bit right around the house. - Diverting surface water somewhere upstream/uphill might be enough. Water might be pooling up somewhere uphill from you, for example, soaking the ground. - You might have a non-porous layer of soil (clay?) a few feet down, keeping the water too close to the surface. It might be enough to just bore down through this layer in a few places, to let the water seep down to a lower level.
All these ideas might be much cheaper, easier, and more effective than what you want to do. Or they might be worse, or might even cause even bigger problems. I don't konw, and it sounds like you don't either yet. Good luck on your research and your project.
-Kevin
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