Difference between grading and backfilling 2

[jpier99463]

I am working on a Corps of Engineers project where every reference to backfilling calls for achieving 95% of a modified proctor. The grading contractor has a contract for grading but not for backfilling. In the cut and fill of grading, doesn't this contractor have to achieve the 95% compaction in 15cm lifts (as required by SOW) in the fill areas as this requires compaction as well. There are no other references in the SOW(i.e. specification) regarding the compaction they are supposed to achieve in their fill areas. What is the difference between grading and backfilling?

 

[sam74]

I believe backfilling would refer to having to excavate for lets say a pipe installation and then having to back fill that excavation to bring to proposed grade

 

[Hoagie]

The definition should be found within the job specifications or in the standards being used for the project (FP-92, State DOT, etc.).

 

[cvg]

your specs should have specifically stated the requirements for fill and for backfill. However, I think your contractor is trying to pull a fast one. You can probably get him on the part that says the final grade should be firm and unyielding. Ask him to proof roll it to prove to you that it is unyielding.

 

[Zambo]

I also think the contractor is trying to play with words to get some extra payment.

Grading to level is basically cut, fill and compact. Backfilling is fill. So it seems to be the same job.

How is he paid per m3 or m2 or LS? What is the description of his pay item?

 

[jpier99463]

The contract calls for the contractor completing the grading portion of his work and then he will be given a new contract to come back later to perform the compaction. The spec calls for 95% compaction everywhere with a requirment that the backfilling happen in lifts of 15cm(6 in). How can you differentuate grading fill work from compaction work? If the contours require 1 meter of fill at a particular location, isn't the contractor required to place this material and compact it in 15cm lifts? How else can you reach the correct grading contours with these specification requirements?

 

[DRC1]

Backfilling unless, as Hoigie pointed out, is defined elswhere, I would say was filling soil na hole excavated for this project. This agrees with Sam72. What you are describing is cut and fill or borrow work. There should be a sepecification for comapction, unless none is desired. That could be the case if there is no plan to use the land for any particular purpose that would require compaction.
On the other hand, I do not see how you will be able to place the material and then compact them at a later time. Something does not sound right. You may have a very defective specification. I would suggest you have an uninvolved 3rd party whom you trust to read the documents and give you an unbiased honest opinion.

 

[cvg]

you may have missed something in the plans & specs, however it also sounds like you have a fishy contractor. Any contractor worth two cents knows that you have to compact in lifts as you place the material and there is no way to go back later and compact it. Unless this is strictly a landscaping project, compaction is required. (even landscaping projects usually have minimum compaction requirements...) Given that, your contractor should have asked right up front what the acceptance criteria was for "fill" or "backfill" or "grading" or whatever you want to call it. I have never seen a military earthwork spec that did not require compaction.

 

[GoldDredger]

Post a pdf of the specification for a read.

 

[jpier99463]

I have taken your advice and uploaded a collection I had put together of all references to grading and compaction in the SOW. There is no specification talking about grading, compaction, earthwork, or anything similar. The grading contractor is performing cuts in excess of several meters and fills of 1 meter and larger. Lacking any other guidelines, based upon the SOW info attached, it appears to me the grading contractor must peform fill work in 15 cm lifts and compact it. He wants to just shove the dirt around into the general final TOPO elevations and then only compact the final 30cm of fill. Is there any way anyone can agree with the contractor's interpretation of the requirements he must comply with.

 

[GoldDredger]

Here is my take on the definition between backfill and fill:

Backfill: Material used to refill an excavation. As in placing 'back' the fill. This applies to the fill placed back for a utility excavation, the material behind a retaining wall, etc.

I would think this would also apply unsuitable subgrade, where deleterious material (or material weakened by contractor operations) is encountered and needs to be removed and replaced with a suitable material.

Fill: Material (dirt) placed where previously there was no material. As in the mass grading of the site where lower elevations are raised to higher elevations.

Regarding the specifications:

Under section 2.3.3 Site Grading and Drainage, the last paragraph calls 'minimum soil compaction shall be 95%...." However this sentence follows an excerpt on holes and depressions being backfilled. (perhaps the contractors confusion, move on this below)

Section 4.13.6 Excavation and Compaction of Fill-- The 95% compaction is referenced, but again is follows placing of fill in areas that has unsatisfactory material.

This section goes on to specify the 15cm lifts, and that those lifs need to be tested for compaction. However, that compaction is not specifically identified there.

On the other hand, the 95% compaction requirement is identified in a few areas. I believe that in 4.13.6 where lift hieght and compaction testing is identified, it could REASONABLY be surmised that 95% compaction is required (in the absence of any other compaction requirement).

Section 2.3.4.2 Parking Areas also calls compaction at 95% for subgrade.

Sect 2.3.3 has an sentence that 'holes and depressions shall be backfilled.' That is a poor choice of words because existing holes and depression are filled via mass grading, not 'backfilled'.

Foundation notes again call for 95%. It also identifies 'backfilling' against underground or retaining walls, which infers a definition similar to mine above.

At any rate, I think your specifications are poor in that they are somewhat vague and subject to interpretation. There should be no question as to what the contractor is required to do.

That being said, I don't think the contractor has much to stand on. He can't just dump a bunch of fill, then compact only the top part, or seek an addition for compacting what should have already been compacted (per 4.13.6).

You might also add that it is a fairly common 'standard of practice' to compact your lifts. Why call out lifts to begin with if you're not going to compact them? If he wanted to do something outside the norm of practice he should have clarified early on.

Good luck, let us know how it turns out.

 

[Dozerman56]

Gentlemen:

'Backfill' is placing soil back in an excavated hole, be it for a retaining wall, foundation, pipe trench, whatever

'Excavation' is removing earthen material from its original location

'Fill' or 'Embankment' is placing earthen material in a new location

'Borrow' is importing new material for placement.

USACE specifications usually have holes in them you could fly a 747 through. Or directly contradict themselves on the most basic points.

Jpier: Read your specifications. The contractor is obligated to provide exactly the work specified, no more, no less. Specifications are worthless? Get ready to approve his change oprder request.

 

[darthsoilsguy2]

Site grading section calls out 95% of the Modified Proctor for compaction. End of story.

Foundation notes call out 95% compaction (of what Proctor? Standard or Modified)

If the grading contractor wants to start a fight about not compacting... they will have to take it up with the General Contractor. The GC is obligated to provide compacted soil under footings by the Structural documents.

We offer an optional service of reviewing specifications on geotech jobs we drill... this service is almost never purchased. When we get on the job for construction testing... it's a total mess. My favorite is when we recommend they use the on-site low-plasticity Silts and Clays for structural fill.... and then the designer leaves the Master Spec in (Only Sands and Gravels are suitable soils)

 

[Dozerman56]

Darth:

Yeah, that's usually one of the first things I check when I open a spec book to quote site prep on a building project. Then send a question as to whether it's the owner's intent to pay us to haul all the excavated dirt that the geotech says is acceptable off site and haul in expensive replacement dirt that'll meet your engineer's spec?

 

[brandoncdg]

Isn't the contractor supposed to follow the soils report and grading plan for instructions on the over-excavate and backfill? No way was this bid without knowing what needed to be done by the contractor.

CDG, Civil Engineering specializing in Hillside Grading in the Los Angeles area

http://www.CivilDevelopmentGroup.com

 

[msucog]

it's a word game more or less. the specs you have call for the soil to be compacted...so if they move dirt, it obviously must be compacted. to me, it sounds like the contractor is trying to differentiate that he's not responsible for backfilling say a building retaining wall during a future phase of construction. i picture what you have described that the grading contractor will grade (cut, fill, etc) the site up to planned elevations. then a different phase will kick off where someone else would be responsible for backfilling the retaining walls constructed during phase 2. i could be totally wrong but that's my guess. but if he's saying that he can move dirt and not compact it, then that's ridiculous and everyone needs to straighten it out asap. compaction required! the specs probably reference a soil's report, or code standard (ie. IBC), or plans or something else. so while there may end up eventally being a conflict between the specific percentage compaction that is required, the odds are very slim that "no compaction" is required.

if necessary, i suggest you get all the contractual details from the owner, include senior staff from your firm in the discussions and go from there. if fill is placed, compact it for goodness sakes. if the fill will go in uncompacted, expect a HUGE mess and possible litigation at some point in time. (i have seen geotechs walk away from such situations due to the additional liability risks associated with being part of such a project)