mini ex to dig big hole

[Yellowdog]

I've dug some 10' deep holes about 8' wide and 20' long but I have a customer asking me to dig a 14' deep, by 8' wide x 20' long hole to lower storage container into. My Bobcat 335 mini is only rated to dig about 12' and reach is only 17.5' and I can only get to two sides of the hole. Trees and a horse paddock are on the other side. I was thinking about lowering the ground around the hole so that my machine initially sat lower for the digging. I've never had to get a hole like that close to perfect but for a container it would need to be close to level. Since I am at my max dig depth, even by lowering the ground around the hole, would it be too difficult to get the material level on the bottom? The ground is hard caliche and possibly has a rock shelf under it. I already told them a hammer might be necessary at some point. My friends that dig septic systems routinely need to hammer and I usually sub to them for that work.
I usually don't use my machine for this type of work (my specialty is mulching, trees, and driveway work) but thought it might be an interesting project to try. I decided to refer it to a septic guy I know because of the depth but wonder if I could have done it? Any advice because I hate walking away from extra work when I will be out there doing trees and driveway work anyway.

 

[superdigger]

I would start on one end of the "trench" and dig down 3-4' and make a bit of a ramp at one end into the "trench" so you can climb back out. With 8 feet of width you would be able to dig down to 14' and swing the material up and out of the hole, then just work your way back out and up the ramp. At the end you would have to dig down an area behind the trench to finish it off. Its not an ideal way to do it, but is certainly doable.

 

[stuvecorp]

I've never dug something like that but my first thought was a bigger excavator but that wouldn't really put money in your pocket. If you could step it down some maybe it would work?

 

[Yellowdog]

I've thought about both ideas--ramp and bigger machine.. Both good points.
Bigger machine expensive and not a lot of room to work.

Down here, some of the septic holes run about $5k plus tanks and simple hookup. It goes up if there is rock. Outside the barn, I'd have to make spoil pile and then move it with Bobcat now and then to have room to work. Guy mentioned he might like it in the floor of his barn.. but not much room inside barn breezeway. That would be really tight but doable if it wasn't so deep. Could dump spoil directly into bed of toolcat and haul outside.

BUT, I'm hung up on that depth. Around here... it's hit and miss with limestone rocks the size of trucks. Caliche is hard enough but I can get through it over time. Limestone almost always takes a hammer or a bigger machine. If someone had to get into that hole and level it by hand or check it with the laser transit, I'd be required to use trench boxes, right? The container will need a crane or big excavator lower into the hole anyway so I can't even set it.
I spend a lot of time referring out work I'm not "comfortable" with and I feel like I am not expanding my horizons. Been doing trees and driveways so long that I'm getting bored and thought "hey, this would be cool" but something doesn't feel right with the depth and not being able to reach the back side. A friend pointed out, that I'd need to go 2 ft bigger on both sides too. The customer gave me the dimensions but after getting the container dimensions, it would be like trying to put on a wet sock... Container is same width and length as hole. Depth ok, though.

Would a backhoe be able to dig that if it can only get to two sides of the rectangle (a short side and one long side)?

Hmmmm. Interesting project for whoever gets it.

 

[coorecat]

I can't see what the job looks like but why can't you just bench it down 3 or 4 feet and and then dig the other 9 or 10 feet out. Is it to tight with trees and horse stable? As for grading the bottom can't you under cut and level with stone?

 

[bigshow]

Bench yourself down in, you stated that you need to be 14' deep, dig down 8' first,carry decent grade on this cut you will be sitting down there later. Now get down to the bottom of the 8' cut and begin digging down the other 6'. The reason for the 8 and 6 cut is that it will be easier for you to maintain better grade with the smaller cut, Also you machine will have more breakout force that may be needed for the harder material that is deeper in your cut. The less you reach the more power you have.

 

[bigshow]

Also, no trench box is required if you lay the slopes back. 1:1 slope for class A material, 2:1 for B, 3:1 for C, I believe.

 

[superdigger]

Bench yourself down in, you stated that you need to be 14' deep, dig down 8' first,carry decent grade on this cut you will be sitting down there later. Now get down to the bottom of the 8' cut and begin digging down the other 6'. The reason for the 8 and 6 cut is that it will be easier for you to maintain better grade with the smaller cut, Also you machine will have more breakout force that may be needed for the material at is deeper in your cut. The less you reach the more power you have.

Only problem with that would be getting the material out of a 8' hole, it would reach up there but you wouldnt be able to put much up before you had to pull it back away from the hole or it would start falling back in...

 

[bigshow]

That's the cost of doing business, either way hes gonna have to bail the spoils back, so you dig the majority out first, while your up higher, so that when your down in the cut you have less to throw up and out, the deeper you are in your bench, the longer your cycle times are. Also when done excavating the first cut, you can move over and bail back your spoils from first the first cut thus giving you room for you last cut with out a lot of wasted motion. Doing deep sanitary it is very common to have a large hoe benching the mainline hoe down in, I've been on jobs where 627's benched me down in. I'm having a hard time explaining it but hopefully you get the point.

 

[xcmark]

If I had a bigger machine that could do it all in one shot without moving things 3~4 times your going to be money ahead. With a mini and a track skid steer you could bench it back and move the spoils with the skid steer but any way you look at it your not getting it done in a day or even two. getting a 5600lb container into the hole with a small machine you may want a ramp on both ends you you have a way out. I know my track machine can lift and pull one end of the container empty but I would need a way out the far end of the hole so your looking at a 40+ long hole , I think a 120+ size machine a renting if for a day . Hammering is extra

 

[Colorado Digger]

if you need the work then go for it. it is very simple and has been stated above. bench it

 

[Yellowdog]

If I had a bigger machine that could do it all in one shot without moving things 3~4 times your going to be money ahead. With a mini and a track skid steer you could bench it back and move the spoils with the skid steer but any way you look at it your not getting it done in a day or even two. getting a 5600lb container into the hole with a small machine you may want a ramp on both ends you you have a way out. I know my track machine can lift and pull one end of the container empty but I would need a way out the far end of the hole so your looking at a 40+ long hole , I think a 120+ size machine a renting if for a day . Hammering is extra

I already told them a big hoe or a crane to lift and place the container. I personally think it's a bad plan to bury that thing. I guess they are cutting a hole in the roof and welding a staircase down into it.

 

[stumpjumper83]

Here is my two cents... Number one, storage containers are rated for above ground storage, maybe to have several units neatly stacked upon them, but definately not to be burried underground. The psi from being burried underground could crush it like a pop can.

Now for how to dig a hole, you say that you dont have enough room for a big machine, where is all the excavated material going? Your going to have 7-8 triaxle loads of dirt that your going to have to find a new home for. I would highly suggest a 120 - 160 sized excavator, or a trackloader (953 style) for this project. Here is why... If you bench down lets say 6 feet, your going to have to put your spoils to the side, elevating that area about 8 feet due to expansion, then your going to have to run around and move all your spoils back so you have room for the next cut of the remaining 8', now you have handled the dirt 2x. Once back in the cut your going to have to place that material to your sides and your not going to be able to get very much out before you have to spread the spoils out again to make more room for the spoils, max dump height can't be much over 10'. Mind you, your only using probably a 1/4 yard bucket, and having to move the material a minimum of 2x.

Bring in the 160dlc deere class excavator swinging a 1 yard bucket, and carrying a 8' flat bottom to a depth of 20'. You can reach 30' to either side with the spoils, no need to handle it 2x. That mathmatically 8x faster than the bobcat, but its actually like 16x faster cause you dont have to track out to move spoils and breakout force of the 160 is worlds apart from the mini.

If you don't have room for the lg excavator, get a trackloader, if you can't get a steel tracked one, go for the largest takeuchi you can get, and get a toothed bucket. Even an old deere 450 loader will do that hole fine. I would highly suggest benching the sides back if your taking a loader in there though. Although if you have room to properly bench back, an excavator can swing around.

Personally I'd refuse to burry a storage container untill I saw specs that indicated that it could take that ammount of side loads.

Now you can somewhat handle the container, probably should use the crane idea.

 

[coorecat]

Like Bigshow says here.

 

[coorecat]

That's the cost of doing business, either way hes gonna have to bail the spoils back, so you dig the majority out first, while your up higher, so that when your down in the cut you have less to throw up and out, the deeper you are in your bench, the longer your cycle times are. Also when done excavating the first cut, you can move over and bail back your spoils from first the first cut thus giving you room for you last cut with out a lot of wasted motion. Doing deep sanitary it is very common to have a large hoe benching the mainline hoe down in, I've been on jobs where 627's benched me down in. I'm having a hard time explaining it but hopefully you get the point.

Like Bigshow says here I've also done some 40' plus benches to get sewer in. It's part of the buisness to go deep you have to bench sometimes.

 

[digger242j]

I guess they are cutting a hole in the roof and welding a staircase down into it.

Getting ready for Armageddon?

 

[KSSS]

Getting ready for Armageddon?

Thats what I was wondering. I have dug similiar holes and if you have a skid steer there that can keep the material away its not bad. Add in Caliche type soil and a small excavator and that can be a long day. Sometimes you have to dance with who you brung however. If there was enough money in it to run two machines for a full day or day and half plus a hammer if you needed it, I would have done it. However, its certainly not a job I would do for marginal money with a mini ex.

 

[pafarmer]

I would dig the majority of the material from on top then build ramp into hole and complete the dig. Out of the hole agin and remove your ramp. Pray for no big rocks. Basically bench your way down in 6 or 8 foot incremants.

 

[curbside]

I've seen some containers buried once but it was for a grow operation "ganja"

 

[xcmark]

I already told them a big hoe or a crane to lift and place the container. I personally think it's a bad plan to bury that thing. I guess they are cutting a hole in the roof and welding a staircase down into it.

I could care less what they want the container in the ground for , as long as they pay the crane to load it in the hole and your getting paid to dig just the hole . I know in the midwest in tornato alley this is more common, but his may also be for unlawfull use also. the walls and room are going to have a huge weight load in them , I would be more comfortable with a 9' deep hole and minimal cover. Only the corners of sea container are designed to carry weight.

let us know how you make out.