Contractor says compaction is fine....here we go

[vato]

After the footing rebar inspection I requested the compaction test results since fill was imported (first note on my foundation drawing of course). After the footing was poured the contractor shows me a letter from a PE who couldn't do the compaction test because it was over 30% oversized material. He, the contractor, decided it was ok to build on. The testing occurred a week before my rebar inspection so the contractor knew darn well that I would have put a stop to the pour without testing. Two questions:
1. Is there a reliable method for determining the soil compaction at this point, with footings on the ground and material too large for a cone test? I've seen those nuclear density testers before. Would that be an option?
2. Can I remove myself ethically as EOR based upon the contractor's deception concerning this matter?

I will be discussing this with the building department. It's a small town and they just let my stuff right on through without understanding it I'm afraid.

thanks

 

[Ron]

Did the PE who wrote the letter state that the compaction was OK? If not, will he?

I realize this is shifting liability; however, the contractor did deceive you and might have used the engineer to assist.

The problem is not likely the field test for in-place density, but the lab test for laboratory compaction standard to be used for comparison with the field test. There are ways to compensate for oversized material; however, if the material was, say cobble sized, it should not be at your footing bearing level anyway, so the contractor failed to bring in acceptable fill material...did the fill meet your specifications? (Hopefully you had a specification for the fill material).

Yes, a nuclear density test can be done, but it runs into problems with oversized material due to disturbance when driving the probe hole. A sandcone density test would likely have been the more appropriate field density test, but that's assuming the fill material was amenable to having a proper laboratory test (Proctor) done.

How heavily loaded is the footing? If heavily loaded (bearing pressure > about 2500 psf, then I would consider some ground remediation under the footing, such as compaction grouting or chemical stabilization. Don't just let the contractor walk from his responsibility....that's one way we've gotten ourselves into these issues because contractors have been allowed to skate in the past.

 

[vato]

I have discussed the situation with the geo that did the original soils report. The contractor got him out there, was told of the problem with the fill, and asked "am i in trouble". The geo just reminded him that the soils report clearly called out the required fill and install methods. So another engineer is hired and tells the contractor the same thing. So I am never told of any of this until after the footers are poured and only because I was pestering the contractor for it. I told the owner that I was not letting this go. He, the owner, happened to be with the excavator when the excavator noticed the difference in what he was using and in the soils report. I reminded him that he paid for the geo's instructions for structural fill. This things a mess with 12" cobbles. At this point if another engineer can sign off on that fill, then they can design the foundation as well. I have written the building department, owner and contractor voiding my drawings. I recommended another contractor to the owner. Not fun and no one to bill.

(During the rebar inspection the formsetter told me they got some big rocks out of there. I was asking about the original excavation, and he was describing the cuts for the footers in the fill)

 

[Ron]

vato...good for you. I think you handled it nicely.

 

[fattdad]

Maximum particle size for controlled lifts of fill should be about 1/3 the lift thickness. So, I'd limit the max size to 3-in, which is consistent with ASTM and AASHTO standards for bulk sampling of soils and also consistent with the ASTM soil description methods.

If you have 5 ft of fill below the footing a nuke gauge will only give you some idea of what's going on in the upper 8 to 12 inches. You also have the problem of the big rocks and some very atypical oversize corrections to both the test results and the reference proctor. I'd say this is just too atypical to be of any use, knowing that the fill includes 12-in diameter boulders.

I like the idea of using a dilatometer when evaluating fill placed without compaction control. You see the dilatometer will give you modulus values that you can then use to determine settlement under the proposed loading conditions. If you are pretty sure that you are not dealing with general shear failure, servicability of the footing is about all that's left. So, if soil modulus values from poorly compacted fill leads to 2 inches of settlement that'd be a problem.

The dilatometer may not work either 'cause you have boulders.

If the uncertaintly is too great, maybe a jackhammer is needed and the contractor just lost a few loads of concrete.

Don't know. . .

f-d

¡papá gordo ain’t no madre flaca!

 

[cvg]

the uncertainty is way too great. The construction is in substantial non-conformance. There is no way you can certify this fill or the foundation without inspection and testing of the subgrade.

 

[vato]

Thanks Ron and Fattdad,
This is sort of becoming enjoyable. I took my letter down to the building department this morning and was lucky enough to interrupt a meeting with the contractor, building inspector, and excavator. I got a little heated, which I was really trying to avoid, but, after I told the building inspector that he needed to red tag these guys because of the above situation, he, the building inspector, accused me of approving the pour without a compaction test. When the county showed up for the rebar inspection, the guy there told him that the "engineer" said that it was ok to pour. The building inspector was actually doing this at the meeting. The contractor is complaining that I call everyone else, but not him. The excavator's telling his story. After the contractor told me that he doesn't need an engineer, "I paid for a foundation design already", I deferred to the building official, who, reluctantly explained to the contractor that, yes, by law, if the EOR pulls his drawings, then he can't build it. I made my exit at that point. Now I'm really upset. Gonna check and see if there's a red tag out there.



(1-I told the "guy" on site, Fred, that I was not even doing an inspection, just checking it out to make myself and the contractor feel better, and THE COUNTY needs to sign off on this. 2-The contractor had previously accused me of being conservative because of my having a lack of field experience. We discussed his lack of experience building from a set of engineered plans today.)

 

[fattdad]

some contractors have one year of experience 20 times over.

f-d

¡papá gordo ain’t no madre flaca!

 

[Drumchaser]

Not that it matters at all but, what is the footing for/under? Are we talking about a building slab? grade beam?

 

[theCorkster]

Take the time to write your daily field reports and send a copy to the owner, contractor and building department. Send a copy of your meeting notes to all parties, and ask for clarifications/corrections. In the future take someone (another licensed professional, preferably) as a witness.

I'll bet this will save you time later on when the question about who pays for the contractor's mistakes comes up. Be proactive in staying involved with this through resolution. It is clear that your absence will be construed to your detriment.

Prepare yourself for the time when the owner, contractor and/or building official look to you and want you to contribute to the "solution."

Not how the world could be, but how it often dysfunctions.