How to dig the narrowest 3' deep trench or minimize sand fill for a wide trench?

[future_vision]

Ok. I am deferring to the power of group think here. Here is my situation. I need to trench 300' for electrical and telecommunication conduit. Electrical is 3" wide conduit and telecommunication will be 2" conduit. The minimum depth for electrical is 30". I am trenching from a pole that is pretty much in the drainage ditch next to the road and up a hill. I am guessing I'll start somewhere around 36" at the pole and be around 3-5' deep when I start ascending the hill. Over a certain number of feet I'll eventually get back up to the 30" (36" to be safe). I think I got that all worked out. Here is my issue. The electrical service is asking for a bed of sand(or stone dust) below the conduit and 12" above. I can't get any answer out of the fiber internet company so I was going to do the same for their conduit. No problem but here is the issue. The telecommunication conduit needs to be 12" away from the electrical. If I dig a wide trench to accommodate both conduits and the spacing, I am looking at a minimum 17" wide trench. Realistically it'll probably be closer to 20". Ok. So what is the problem? The problem is the 12" of sand on top of the conduit. How do I get 12" on top of both conduit and not have to buy a ton of extra fill for the 12" gap in between? I had considered renting a trencher but that might be a little treacherous on the slope and I would need to put a much large gap in the rock wall to navigate through. Plus, being in New England, I'll likely hit some large rocks. Then what? It's not like you can just bend 3" around them or dig multiple new trenches hoping to find a clear path. There is also the fact the electric company only allow a certain amount of bend in the run and I already need to do a 45 degree turn at one point.

A trencher, that can go that deep, is about $310/day from Home Depot. I'd have to do some serious looking to find one somewhat local for cheaper. The easy route is just do the wide trench with the CAT 306 but the cost of filling that 12x12x300 area, in between conduits, is prohibitive.

 

[dodge man]

300 feet isn’t that far. If you’re worried about rock rent a mini excavator with a narrow bucket. You could also do two separate trenches.

 

[LittleBittyBigJohn]

Want to see what's NOT necessary...? I went 48" deep with a 42" wide bucket. I won't do that ever again, I fought that trench for a year before it finally quit settling and needing more fill. I'd do it with a trencher as deep as you can possibly get, sand if required, throw the electric conduit down then sand to about an 18" seperation then throw the 2" conduit in on top of that. Or 2 trenches, the go pretty fast. Otherwise if you have a mini-x with a reasonable width bucket, use that and kick each conduit to the sides of the trench. Sand is cheap around here, whatever you will have to buy is going to be a lot cheaper than what you will spend on conduit for the project.

 

[4570Man]

I wouldn’t separate the lines horizontally. Dig the trench as narrow as the bucket you have and put 12” of sand over the electric. Once that’s done put the second conduit in. It’s still 18” or more deep.

 

[future_vision]

300 feet isn’t that far. If you’re worried about rock rent a mini excavator with a narrow bucket. You could also do two separate trenches.

I'm already renting a CAT 306 for a month for some other bigger tasks. I can possible rent another excavator. That would be cost prohibitive. That and a narrow bucket is still going to great a wide trench. I looked at the micro trenching buckets, and thought the was the solution, but you can get down 3' much less 4-5'. You are limited by the width of the connection regardless of how thin your bucket is.

 

[LittleBittyBigJohn]

How wide of a bucket is coming with the 306?

 

[future_vision]

I wouldn’t separate the lines horizontally. Dig the trench as narrow as the bucket you have and put 12” of sand over the electric. Once that’s done put the second conduit in. It’s still 18” or more deep.

Hmm. Two problems with that. One is that having the telecommunication line on top of the electric means that i need to navigate that line if I need to get to the electrical below. I'm not sure I really want to do that. Second, the sand is intended to protect the conduit from rocks when/if compaction occurs. Do I really want to protect the electric and not the telecommunication conduit? I really wish that the fiber company can give me install instructions. They just don't have them available. I kept getting bounced around on two different occasions. Eventually, they submitted a ticket to one of their divisions. I am not keeping my hopes up I'll get any guidance. I'm considering calling a competitor that runs co-ax. Probably Xfinity. See what they say

 

[future_vision]

How wide of a bucket is coming with the 306?

Good question. Didn't really think of asking until today. I need to call them in about an hour or so to pay for it. I'll ask then. The plan is to use the CAT for large stump removals, digging out a walkout basement and other land grading. I'd prefer a bigger bucket for that. Maybe i ask them to throw a narrower bucket into the rental. Depends on the price. I don't really want to rent a bucket for a whole month that I am only going to use a couple of days.

 

[LittleBittyBigJohn]

Surely they will let you trade it out. But if you already have the machine I'm not sure I would spend a bunch more money on more rental equipment trying to save a little bit on sand. Possibly a trencher, but that would be just to save headache on backfill. One good advantage of a wider trench is being able to get down in it to glue your joints.

 

[RayIN]

Whatever you decide, be sure to take pictures at each stage; not only to document the project but also for future reference when a problem arises. It's visual evidence of its location in relation to the house and outbuildings. Then you know exactly where and how deep the conduit is located.
I'd use stone dust, instead of sand; regardless which, it will be hard dirt 30 years in the future.

side story. In 1968 I dug out for building a basement in red clay soil, and back-filled with the same dirt after the house was completed.
Fast forward to 2014. I had to have the basement drain replaced due to tree root damage.
Where the backfill was over the drain, it was now sandstone, solidly in place against the basement wall, top to foundation. It had to be sawed into chunks then split away with wedges.
There was no evidence of the sand above/below the drain line.