Question on back hoe speed

[dirtworksequip]

mx125, if your soil conditions will allow you to use a trencher you could probably do the 2200 feet of electric service trench on a weekend. IF THE SOIL CONDITIONS ALLOW. Are you gluing up the conduit and backfilling the trench. If you are you will need some help. The way I would do it with help is glue up the conduit first. You could actually glue it all up if the terrain permits. Lay the conduit off to one side of where you are going to trench. Out of the way of the trencher. Now start trenching. When you have about 100 feet of trench done have a helper start putting the conduit in the trench working towards the trencher. Once that 100 feet of conduit is in the trench you can start backfilling the trench with your tractor. Provided you have either a loader,rear blade or front blade. Keep trenching ,laying conduit and backfilling. With two other friends things should go pretty smoothly.
Let us know how you make out.

As far as the geothermal of "500 feet per ton" that may be 500 feet of pipe per ton and if they slinky the pipe it doesn't take 500 feet of ditch. $6,000 seems high, but I don't know what the rates are for your area.

Sincerely,Dirt

 

[CurlyDave]

I'll also add teh odds of getting the foundation depth correct and level are virtually nil which would mean the odds for increased settling would likely be great. You know, cracked walls and such.

sixdogs:

Why would this be the case?

I have always thought that if the foundation were deep enough (far enough below the frost line), there would be no such thing as too deep, and unless there was a consistent slope in the foundation trench bottom in the same direction on all four sides, and maybe not even then, a minor slope on the bottom would not cause a problem.

Oh, it might require some more concrete, but there is not going to be excess settling if the foundation trench is clean form debris and loose earth.

I usually use a coefficient of friction of 0.4 for the earth-concrete interface, which is conservative. If we ignore any resistance to concrete motion from material on the sides of the trench, there would have to be a consistent slope of 23.6 degrees on the bottom of the trench for the foundation to move. In the actual situation, material on the sides of the foundation will provide even greater resistance to movement.

Essentially, I don't think it is possible for even a blind man to dig a foundation trench which would cause settling or wall cracking. OTOH, a foundation which is under-designed, with either not enough soil bearing area, or not enough depth, will cause cracking & settling.

 

[mx125]

mx125, if your soil conditions will allow you to use a trencher you could probably do the 2200 feet of electric service trench on a weekend. IF THE SOIL CONDITIONS ALLOW. Are you gluing up the conduit and backfilling the trench. If you are you will need some help. The way I would do it with help is glue up the conduit first. You could actually glue it all up if the terrain permits. Lay the conduit off to one side of where you are going to trench. Out of the way of the trencher. Now start trenching. When you have about 100 feet of trench done have a helper start putting the conduit in the trench working towards the trencher. Once that 100 feet of conduit is in the trench you can start backfilling the trench with your tractor. Provided you have either a loader,rear blade or front blade. Keep trenching ,laying conduit and backfilling. With two other friends things should go pretty smoothly.
Let us know how you make out.

As far as the geothermal of "500 feet per ton" that may be 500 feet of pipe per ton and if they slinky the pipe it doesn't take 500 feet of ditch. $6,000 seems high, but I don't know what the rates are for your area.

Sincerely,Dirt

Thanks Dirt. That gives me some great info. I'll take that back to my builder friends and will be better armedin the dicussions.

And Curlydave . . that also gives me a little more confidence. I'll get a price from my foundation excavator . . if it's a meaningful chunk, maybe I'll go it alone on that garage.

Thanks everyone!

 

[dirtworksequip]

mx125, I checked with the owner of the geothermal sytem about the runs I dug. They were 5 feet deep,3 feet wide and 150 feet long. The pipe he used was in 600 foot coils. He used 600 feet per 150 foot of ditch using the slinky method. Also had 4 runs for the 4 ton unit.

Hope that helps.

Sincerely, Dirt

 

[mx125]

mx125, I checked with the owner of the geothermal sytem about the runs I dug. They were 5 feet deep,3 feet wide and 150 feet long. The pipe he used was in 600 foot coils. He used 600 feet per 150 foot of ditch using the slinky method. Also had 4 runs for the 4 ton unit.

Hope that helps.

Sincerely, Dirt

Thanks. That makes more sense. I spoke to a pro excavator today. He said that although he hasn't done any geothermal work, he "assumed" he could excavate a very large rectangle 6 feet deep . . allowing them to run all the piping they'd need . . .and that he could easily dig for $1500. Back fill would be less . . . so unless "trenching" was required he'd see $2500 as a more realistic quote (vs $6-7K quoted by the geothermal installer).

Perhaps the geothermal thermal process requires a more undisturbed soil .. but I'll ask the geo guys.

 

[CurlyDave]

he "assumed" he could excavate a very large rectangle 6 feet deep . . allowing them to run all the piping they'd need

You need to be a little careful here. The idea is to exchange heat with the earth. You would need a rectangle larger than the area of the trenches combined, because there are "edge effects" with the trenches which you would lose with one big rectangle of the same area as the total of the trenches.

While I might be able to muster up enough math to do this calculation, it is not for the faint-hearted.

I would want the hydrothermal factory engineers to make this calculation, not just a local installer.

 

[sixdogs]

My comments regarding getting the foundation hole straight and level means that is is difficult to get the dig even all over the length of run and that some "filling" may be necessary to correct too deep of a dig in one area. If that happens the soil will settle later and odds of a foundation shift are more likely.
I don't dig foundations but have seen a lot dug buy pros who seem to take a lot of care to get it exact and right the first time to avoid the settling.

 

[CurlyDave]

some "filling" may be necessary to correct too deep of a dig in one area.

Unless the slope is way, way off over a substantial run, don't fill with dirt, just use extra concrete.

If I am doing it myself, I also use extra steel. The money I save on the excavation more than pays for a little extra concrete and steel, and I get a stronger, better foundation for less money.

 

[dirtworksequip]

mx125, you need trenched runs and not one huge excavated rectangle. The runs I did were 15 feet between the runs. In other words it was layed out
3 foot trench then 15 feet undisturbed soil between the runs.Then another 3 foot wide trench followed by 15 feet of undisturbed soil. Each 3 foot trench had 15 feet of undisturbed soil between them. The idea of the geothermal system is to affect as much ground area as you can. Hope that helps you see the picture. If you put the piping in one big retangular hole you will be excavating out a lot of extra dirt and not affecting as big of an area.
Wish I had some pics of the system I did and you would get the idea. The $1,500 would be inline with what I did. If I remember right I think the total was $1,750 and that included the time for a machine to backfill. One word of caution is you need rock free dirt to bed the geo pipe in the trenches. We had an over abundance of topsoil, so I roto tilled the topsoil to a powder with my JD 3520 equiped with a JD 660 tiller. Then we used a Cat Track Skidsteer to slowly backfill with the powdered topsoil. Had 3 guys in the trench with shovels backfilling the first couple of inches to make sure no rocks were against the pipe. Once we had a couple of inches over the pipe we backfilled the rest of the trench with the Skidsteer. Its critical to make sure there are NO rocks in contact with the pipe.

Sincerely, Dirt

 

[mx125]

mx125, you need trenched runs and not one huge excavated rectangle. The runs I did were 15 feet between the runs. In other words it was layed out
3 foot trench then 15 feet undisturbed soil between the runs.Then another 3 foot wide trench followed by 15 feet of undisturbed soil. Each 3 foot trench had 15 feet of undisturbed soil between them. The idea of the geothermal system is to affect as much ground area as you can. Hope that helps you see the picture. If you put the piping in one big retangular hole you will be excavating out a lot of extra dirt and not affecting as big of an area.
Wish I had some pics of the system I did and you would get the idea. The $1,500 would be inline with what I did. If I remember right I think the total was $1,750 and that included the time for a machine to backfill. One word of caution is you need rock free dirt to bed the geo pipe in the trenches. We had an over abundance of topsoil, so I roto tilled the topsoil to a powder with my JD 3520 equiped with a JD 660 tiller. Then we used a Cat Track Skidsteer to slowly backfill with the powdered topsoil. Had 3 guys in the trench with shovels backfilling the first couple of inches to make sure no rocks were against the pipe. Once we had a couple of inches over the pipe we backfilled the rest of the trench with the Skidsteer. Its critical to make sure there are NO rocks in contact with the pipe.

Sincerely, Dirt

Thanks Curly and dirtworks. I definitely understand what you mean. And I don't wat to spend $35+K on a system that doesn't work well dur to improper trenching. I'll talk to the geo team. If he has complete specs for the trenching I'll talk to my pro about cost on his end. Thanks again for all the insight.