Water Line Trench, Big Problems

[LiketoFix]

If you can pump the Water table down and remove MOST of the Water/Moisture in the trench and you can backfill with semi dry sandy/clay soil that you have as it'll somewhat protect the line as much as possible. A sleeve as someone suggested earlier over the new line to prevent future possible damage will really help to protect the line during back fill and future problems as when your done you don't want to re visit this EVER!
Done this as a Contractor for Years and never Had to go back and re do!!!
Once the line has about a foot of sandy clay like,(soft), back fill then if it was under a hard surface like a drive way, slab, garage floor, I would compact granular, stone base, Fill Material and don't look back.
I still Don't know where your located as far as Frost line,(Winters), and availability on Limestone Back Fill! My Favorite! As I made a living installing several Thousand Tons of Limestone Fill as Needed and Required!
Nice Job on getting the line in and as an alternative to a sleeve the Foam pipe insulation with a perforated slit in it with Zip Ties will Do if you so choose. Not only protecting the line with a foam cushion but also as an Insulator to your water line. JMO!
Good Luck!
LtF

 

[Mattilac]

Thanks everyone. I did install PVC sleeves under both footings to protect the PEX from abrading against the bottom of the concrete. I did not sleeve it anywhere else though... I'm hoping the PEX will be protected enough just from being pushed down into the sand/mud.

I spoke to a geotechnical engineer and showed him what I have going on. His recommendation was not dissimilar to many of yours:

1. Pump out as much water as possible, and then keep the pump running as needed to keep the water level low.
2. Lay down filter fabric to keep stone from sinking into the mud/sand
3. Dump and spread a decent layer of 3/4" stone in the trench so the remaining water has somewhere to go.
4. Backfill with the sand that came out of the trench. Compact in 6" lifts until it's filled.

He warned that the sand may not compact very well, in which case I'd want to get some proper fill. Obviously I'd like to reuse the sand so that I can save money and not have to move it all somewhere else. So we'll see how it goes.

I'm going to rent a compactor. What type do you guys think I should rent for fine sand? Plate compactor or jumping jack? What size?

 

[LiketoFix]

Mat,
As far as the Compactor that you use you have to be careful not to over compact the fill close to the line and I suggest at least a foot of fill on top of the line for a type of protective cushion if you will. I like the Idea of the Filter Fabric to separate the Stone from contaminating into the sandy soil back fill. As far as which type of Compactor typically a jumping jack is common for a trench as a vibratory plate tamper will work especially in 6 inch lifts. Use common sense as over tamping will bring any remaining trench water up to the surface and you won't be happy.
LtF

 

[larry4406]

Any value in installing vertical pvc standpipes with end capped and perf holes around the perimeter? He could connect a suction pump and continue dewatering as he is filling?

 

[ycgoat]

Definitely a plate compactor the foot tamp might just dig a hole

 

[Ole Slewfoot]

Here code says we need a protective sand surround and tracer ribbon. Makes sense.
If you rent buy or borrow a gas pump, you should be able to pretty well dewater the trench in fairly short order. Personally, my first try would be to buy a used pump reasonable, and sell it on after.

 

[Innovate1]

With that much water I expect a compactor will just sink in the mud. Fill it in and in late summer it should have settled and firmed up enough to regrade.

 

[Mattilac]

Got the filter fabric and first layer of stone in. It definitely firmed up most of the trench bottom, but some areas are still squishy, even through the stone. I'll give it some time and see if this stone/fabric/pump set up will draw more water out of the super-saturated soils. I'm leaving the electric pumps running overnight to keep the trench from just filling up again.

Glad I didn't rent a compactor this morning. It would've been a waste as it took me all day just to get the filter fabric and stone laid in. Maybe I will try to rent one on Friday and hopefully get the weekend at a 1-day rate.

 

[Mattilac]

Hallelujah - the pumps are finally off and we are high and dry. I've got the trench backfilled to about a foot below grade (where I will lay down the 'Caution: Buried Water Line' detectable tape). I put all the original sand/silt back in and compacted it every 6" on the way up. It feels pretty good - no softness anywhere.

Now I'm wondering what I should finish backfilling with? The original top soil is full of roots and sticks and junk. It never had nice grass on it. Should I just put all that back in or should I consider getting a truckload of something else?

 

[Ole Slewfoot]

The organics will resist compaction, then rot away in a year or two...might not matter depending on your landscape vision.

 

[larry4406]

Good success on the water service trench.

How are you getting power to the structure?

 

[LiketoFix]

Save your $$ that material that you have on the side will work just fine and with a little elbow grease so to speak, as you have demonstrated, pick out the roots and debris from your cast spoils to discard and plant away. My neighbors we're impressed with my approach to the landscaping in our area when I fine graded my area with the existing soils,(country living), and didn't over Topsoil,($$$), and I can actually pick up leaves when wet, and we get a lot, in the fall with my Cyclone Rake and Tractor without tearing up the yard. It's no Golf course but a nice lawn in the Spring/Summer/Fall months. JMO!
Nice job on your project!!!
LtF

 

[Milton Shaw]

One of my wife's uncles died and they could not bury him for more than two weeks because of the ground water in the grave. They ran a large pump for two weeks and never did get it dry enough to keep the casket in the ground in that two weeks. Finally it quit raining every day and were able to get him buried in a concrete box with the casket inside. Just be glad it's only a water line

 

[Mattilac]

Thanks for the input. I don't know much about soils or landscaping. It makes sense to just sift out the major roots and debris and push the same dirt back in. Do I compact it or don't bother? I want to be able to drive vehicles (including a heavy telehandler) around in the yard while I frame the building over the next several months.

How are you getting power to the structure?

Electric will come from the other corner of the house. If I do go underground, it will be a much shorter and shallower trench. Should be way less painful.

 

[LiketoFix]

Thanks for the input. I don't know much about soils or landscaping. It makes sense to just sift out the major roots and debris and push the same dirt back in. Do I compact it or don't bother? I want to be able to drive vehicles (including a heavy telehandler) around in the yard while I frame the building over the next several months.



Electric will come from the other corner of the house. If I do go underground, it will be a much shorter and shallower trench. Should be way less painful.

Since your going to run the telehandler and your doing well with your work! I would continue to back fill with the soils available that you have and by all means YES Compact to the top and if you happen to go slightly higher when back filling don't worry as when your project is complete the last and I mean very last thing that you'll do is fine grade the area and place top soils as needed and plant Grass vegetation as you like conducive to your areas.
LtF