Difference between grading and backfilling
Difference between grading and backfilling
(OP)
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?





RE: Difference between grading and backfilling
RE: Difference between grading and backfilling
RE: Difference between grading and backfilling
RE: Difference between grading and backfilling
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?
RE: Difference between grading and backfilling
RE: Difference between grading and backfilling
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.
RE: Difference between grading and backfilling
RE: Difference between grading and backfilling
RE: Difference between grading and backfilling
RE: Difference between grading and backfilling
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.
RE: Difference between grading and backfilling
'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.
RE: Difference between grading and backfilling
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)
RE: Difference between grading and backfilling
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?
RE: Difference between grading and backfilling
CDG, Civil Engineering specializing in Hillside Grading in the Los Angeles area
http://www.CivilDevelopmentGroup.com
RE: Difference between grading and backfilling
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)