Backfilling basement retaining walls

[BruceWard]

Edit: Looking at those pictures in post 19, Man that was quite the undertaking, getting that site ready!
Don't know how high that hill goes up above you, but if it's huge, might want to get those machines back there and do some serious storm water control up above the house.

JB.

Uphill is South.

It turned into a bigger project than planned. We knew it would be rock but did not know how hard it would be. If the Komatsu 300 could have dug out the rocks it would have been over in about 4 days. That thing moved over 800 yards in the 3 days it worked.

The hill peaks less than 5' above concrete walls. I need to measure it more precisely for the perk test as we are planning to use a leech field on the other side of the hill and hope to trench through it for a gravity flow system.

This picture is taken from the top looking toward the house after the excavation but before the concrete. The concrete walls would be roughly centered.

We have had a week of heavy storms. A few flash floods and 2.5" in the rain gauge. Water was running 6" deep through the culvert on my driveway today even though it has not rained for 24 hours. It was clear that water had run out through the drain pipe. The are around the slab, walls and footers was dry. The city pit was where I left it and well packed by the rain but will need to dry out before I can get the concrete truck in there.

 

[JB4310]

If you only have five feet above you, that should be fairly easy to manage the run off.

Be careful bringing in that concrete truck close to the walls, I'm not familiar with "city pit" fill. But around here clay is very unstable, our red/brown clay is the last thing you would use for back-fill (made great bricks). Once it gets wet, it stays wet forever, like working on a sponge.

Where do you need concrete, over that storm room?

JB.

 

[BruceWard]

The concrete is going over the storm shelter.

The "city pit" product is also called crusher run or bank run. It is produced by using a large dozer to push across the top of a lime and shale area. It is the choice material for road base in my area. In fact my supplier had a problem recently that the state said it was compacting too much. When it is loose it asorbs water. Once it dries out it is similar to concrete. In my experience water runs off of it and even when water pools it does not penetrate the city pit. I was planning to use it for backfill as it is one of the least expensive materials that I can get. A local waterproofing company that bid on my job also recommended it. There is 800 yards of it on my driveway. It has not washed at all since installation in 2008 and has handled heavy equipment, concrete trucks and many many dump trucks without a problem.

Looking in.

Looking out, the ramp to the road is greater in depth than the back fill area.

The concrete truck is supposed to come on Thursday. If it does not dry out before then I will have to reschedule. We will bring the 40,000 pound excavator over and test the backfill area with the bucket before the concrete truck arrives.

I found some jobs for the excavators with my neighbors so the equipment is still on site.

 

[2manyrocks]

These pics are taking a while to load. How about resizing the next batch? MS used to have a free image resizer and now I think it's built into Win 7.

Nice view of the river. Makes it more interesting to see why you're building where you are.

 

[JB4310]

That city pit sounds like good stuff. I see why you say a trench drain shouldn't allow much water to permeate into the soil. I would still build in the maximum amount of pitch, maybe use 6" ads.
The mixer shouldn't have to get to close, they usually carry some extra chutes?

JB.

 

[BruceWard]

The truck will be one of these

They have a 25' or 26' front chute. The slab is 14' x 14'. My guess is the front end will be about 10' back from the corner of the wall facing the corner. The majority of the weight will be even further back.

Thanks for all the advice.

 

[955Lincoln]

Thanks for taking the time to post the pics and stepping us through the process. Was there an unforeseen reason that you excavated too deep? Like having to place the front wall farther back than calculated? Your before pic looks exactly like my land does right now and I'm planning for a walkout too.

 

[BruceWard]

Thanks for taking the time to post the pics and stepping us through the process. Was there an unforeseen reason that you excavated too deep? Like having to place the front wall farther back than calculated? Your before pic looks exactly like my land does right now and I'm planning for a walkout too.

Before building I considered having a civil engineer friend draw a profile of the land to decide upon placement of the house and driveway. I knew it would be difficult for the excavators to work to a predrawn plan as the rock would determine where the house would be. So I provided the excavators with a diagram and marked corners and elevation before and remarked as we worked. I failed to account for the slope downhill toward where the house starts. If I were doing it again I would consider excavating shallower and adding fill to reduce the slope (runoff) toward the house. Although I needed to excavate 9' deep to have the whole foundation on undisturbed material. If I had excavated 7' more than 8' of the depth of the house would be on fill. Considering the two options it is probably better to have water running toward the house than to have 1/5th of the foundation on fill.

 

[955Lincoln]

OK thanks! I didn't understand about the depth of the house vs. slope and undisturbed ground. Got it now, less slope or smaller depth dimension of the structure the higher the house could be on undisturbed ground :thumbsup:

 

[AGGIE00]

Since you brought this up..... I've got a house with a crawl space where the ground slopes into the back wall. I'm seeing wet block in the crawl space--it's dark from moisture. I suspect there is no footer drain at all.
I want to get this corrected.

Do you think I'd better off installing a footer drain in crushed gravel wrapped in geotextile fabric or should I come out further from the house and dig a french drain or swale?

Have you considered having closed cell spray foam applied to the floor and joists? It would have to be done when everything is dry and clean, but you would get not only the vapor barrier you want, but also a substantial increase in the efficiency of your home.