[Fine Edge]

Have been contracted by a pool company to install a natural stone water feature on the edge of their pool which will use large ( 500 lb. - 2000 lb. boulders).
Size of concrete pad will be 10' wide x 3.5' deep.
I have over designed the base doing a monolithic pour and 3 18" wide piers on the front + 12" concrete for base, rebar, etc....

The pool company is excavating the pool and will dig out our base for us but when I got over there, he had used the excavated soil and placed it exactly where our base will be.
To make matters worse, the backside of the pool ( where our water feature will be ) already had 2 1/2' of fill.
Now the excavating company tells me that his Bobcat T190 has sufficient ground pressure to compact our base and that we can just dig out and pour.

My feeling is that I need to get below existing ground level for my base and not rely on builders backfill and pool company's backfill - or get a compaction test which I feel confident will not pass.

What are your thoughts on this compaction issue?
I'm 95% sure of the correct answer but this site certainly puts my mind at ease for almost all of my dilemmas, big or small.

[Rich678]

I think you've got the right idea. I would definitely get a soil test and or engineer consultation. A bobcat T190 is a heavy machine, but with those tracks, it actually does less compaction than a wheeled machine. Also given the depth of the fill, is it going to actually compact all of the soil layers, or just the top layers. I could be wrong, but I would be just as apprehensive as you are. CYA my friend, because with boulders like that... there are no easy problems. Good luck

[HRLand]

This excavator sounds like a clown. Follow your gut.

[PSUscaper]

I know the right answer and I believe you do too.

But my question is who is taking responsibility for the waterfall? If you are being contracted out by the pool company and they are taking liability, then it is not necessarily your problem.

I would have a conversation with both the pool company and the excavator and explain to them your worries. If you plan on keeping a relationship with them and do not want to sacrifice quality for the sake of their screw up, then say it. If they don't get it, then it is probably a relationship you don't want to continue and should walk away from now. It may help them learn the correct way to do things, and the next job they get you guys will all be on the same page.

[Stonehenge]

I agree with Penn, figure out where liability and loyalty lie before deciding what to do.

As for the ground pressure of the T190 - when tauts the 4.9 PSI ground pressure of that machine as a selling point, it's safe to say that is not enough pressure. I mean jeez, tracked machines are known for their dispersement of weight.

So yeah, as others have said, you already know what the right answer is to do the job right - remove all disturbed soils down to virgin soil.

[Raj Venugopal]

The right thing to do is normally the most inconvenient and difficult.

[Stonehenge]

Originally posted by Raj Venugopal
The right thing to do is normally the most inconvenient and difficult.

That's what I always tell my guys!

"If you're wondering what to do in a certain situation, think of the most difficult way to go about getting the job done. That's probably how I want you to do it." - Jeff Pozniak, at least twice per season since 1997

[HardScaper26]

I think that you definately need to stand behind your opinion of how to get it done. A bobcat T 190 is a heavy machine, however doesn't excerate a lot of ground pressure. Afterall, if the pond fails, who will be responsible?