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Construction & Contractors/Organic matter in base course material for roads


Dear Sir, my question is related to the Engineers intension to deduct a certain %age form the BoQ unit price for road base course material, if the specified requirements are not met from the material available at site borrow areas, though tested for long time by the Contractor.
Though this is a question to be resolved on contractual support and arguments, however as the Engineers intends to reduce the BoQ price for some deviation of tested material from the specified limits, therefore I need your technical argument and support about the weightage and role of the organic matter content and its effects on the life and stability of the road structure, to plea against the Engineers position.
The Contactor has processed the raw material from the contractually designated borrow areas to prepare the base course material to be used in the construction of dam crest road. All other specified limits/parameters have been met, except the Organic matter content, when tested in the contractors site laboratory.
The Technical Specifications stipulate this limit to be less than 0.1%, but the results achieved at Site from the material tested are 1.9% (higher than the specifications). Now the Engineer intends to reduce the BoQ unit price by 50% for this non-compliance of the technical specifications.
The Contractor does not agree and insists on full payment.
MY question is:
1. does the Engineer has the contractual basis to reduce this rate for this non-compliance in respect of the organic matter content, though we have used the raw material from the designated borrow areas as shown in the tender documents and then processed in the processing plant?. These designated areas are shown on the tender drawing and the tender drawings being part of the Contact. The Contractor cannot search other borrow areas to satisfy the technical requirements, which may involve extra cost (it is the contractual part of the question, not related to your technical response).
2. the Engineer may stick to the contract interpretation and may argue that the Contractor should have satisfied himself before signing the Contract; the Contract comprising of the Technical Specifications, showing the technical specifications requirements for base-course material as well.  The Engineer may state that the Contractor should therefore bear this cost by way of a reduced payment for this material it is the contractual part of the question, not related to your technical response.  
3. If the Engineer still insists and if the Contractor compromises, then what should be the % weightage of the organic matter component and its effects on the design life of the road structure (it is related to your technical response) , to be considered for such deductions from the BoQ unit price, if the specified requirements for the base course material are as follows:
1. gradation, 2. Dry density, 3. Plasticity 4. California Bearing ratio 5. Los Angeles Abrasion 6. Organic matter component
Please note that except Organic matter content, all other requirements have been met, when processed material was tested in laboratory.
Also advise me what should be the criterion, while determining any such % weightage of the Organic matter content for deductions from payment. Shall this % weightage of the organic matter content in the base material be on the basis of its negative effects on the life of the road structure or some other considerations?.
Waiting for your valuable response. Regards

Here are my reactions to your questions in numerical order:
1.  Not knowing the details of your contractual language, I can only respond generally.  

Whether the Engineer has the contractual basis to reject materials coming from its own designated source is an issue that commonly arises, and is dealt with in the fine print of the contract.  

In the areas where I practice, many highway agencies have stopped designating sources in large part because of these issues.  Geologic characterization of a material source does not cover all factors that impact the suitability of the material as it is eventually delivered and placed in construction.  As one example that may be relevant in your case, suppose the Contractor does not strip overburden to the extent that the Owner might have assumed, and then produces material that holds excessive fines or organics, or that is more weathered and therefore breaks down during handling and placement.  Moreover, the Owner seldom has the facilities for conducting a full-scale mock-up of the crushing and processing plant the contractor will eventually use; suppose the material turns out to be more friable when processed in bulk than it did when processed at laboratory scale.  Or perhaps the contractor chooses to incorporate the less favorable components of a heterogeneous deposit.  

Because so many of these variables (aside from the geology, of course) are under the control of the Contractor, highway agencies either no longer designate sources, or include language in the contract making the suitability of the materials the Contractor's responsibility.  An important part of such language is other language expressly stating that the data characterizing the deposit or source is advisory in nature and not to be relied upon without confirmation by the Contractor.  

Of course, some contractors nonetheless complain about the quality of materials in designated sources, but it does give the Engineer the means to identify measures the Contractor is obligated to use to assure the acceptability of materials.  Whether your contract includes those provisions or not, I of course cannot say.

2.  This question is partly addressed by my answer to (1) above.  Engineers are very fond of transferring risk to the Contractor, and sometimes make this transference too casually.  In such cases contractors have often persuasively argued that they are no more equipped to fully characterize a material source than the Owner, prior to bid.  They will often cite constraints on access, permits, environmental constraints, time, and so on that prevent them from conducting suitably-sized bulk handling and processing trials.  There often is some merit in this, but more often it is merely because contractors bid a lot of work and can't afford to run around testing all material sources on every job they come across.  

So when a dispute arises, those are the issues that come up -- the Owner saying it is the Contractor's risk, and the Contractor saying such allocation of risk is improper because, in view of the representations of suitability the Owner has made through the bid documents, the Contractor is not in a reasonable position to reduce that risk still further.  

When there is a large volume of material involved, savvy Owners have let small contracts or allocate additional front-end time for bidders to recover and process large volumes of material.  This is common in dam construction where large quantities of materials are to be handled and placed, and it goes a long way toward reducing disputes.

3.  This is the technical aspect of your question.  I am not the world's expert on base courses and would first recommend that you consult the literature on what a reasonable percentage of organics would be before the performance of the base course is degraded, but I cannot see how 1% or less of organic content would much degrade a base course's performance.  There are mitigating factors, for example organics can sequester calcium and magnesium which can reduce the effectiveness of cementitious amendments (assuming lime or cement treated bases are used).  Mostly the concern is that high organic content will impede compaction, and eventually degrade and leave voids behind, resulting in a less dense layer that offers less support to the surface courses, and/or that organics can result in chemical instability that can attack and degrade some mineral components of the base course.  

There is no widely-accepted limit for organics in base courses that I know of, although others may.  The requirements I have seen most commonly say "free" of organics, and I suspect, though I could be wrong, that the basis of your specification limit of 0.1% represents nothing more than a number low enough as to be essentially zero, so that the base course can be said to be "free" of organics. There may be some higher number that could rationally be developed and shown to be consistent with long-term base course performance, but that would have to consider the nature of the organic materials in your particular aggregate, the climatic conditions (a road across the top of a dam is not subject to cross drainage, for example), and the performance requirements (how high are the accumulative wheel loads from traffic, and what are the consequences of degraded performance).  

I of course cannot opine on that, not knowing the details of your project, but an organic content of nearly 2% does seem high, and it seems like proving the acceptability of that material would be difficult.  Even if the material meets the CBR and LAA specifications, eventually as much as 2% of the material comprising the compacted volume may disappear, and the collapse of the resulting voids could eventually have a deleterious effect on the surface course.   

I would also further comment that the only curative for the non-spec base course that you have described is a monetary penalty.  Monetary damages are often exacted as penalties for conditions, the consequences of which are not purely financial.  In my opinion it is better to first seek a technical, rather than financial solution.  I can cite one instance in my experience where where the base course contained too high a percentage of clay; rather than buy an undesirable material for less money, we required the contractor to amend the material with lime, at his cost.  In your case perhaps the contractor could be required to remove the nonconforming material and blend it with better material, at his (or some shared, negotiated) cost, or provide a second layer of better material leaving the nonconforming material in place, or meet a significantly higher compaction level (thereby removing voids initially to mitigate the development of further voids over the long term).

I can't say more without knowing the details of your contract and the construction conditions.  I am available of course for engagement on a professional basis.

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Robert Cummings, P.E.


I can answer questions related to rock blasting, rock and soil excavation (such as tunnels and highway cuts), stability of such excavations, and foundations in rock and soil. I can also answer questions related to geology and mining.


30+ years as a geotechnical engineer and minerals engineer. Active consulting practice in rock blasting, geotechnical engineering, and rock mechanics for mining and heavy construction.

Society of Mining Engineers, Deep Foundations Institute, Association of Engineering Geologists, and International Society of Explosives Engineers.

Mining Engineering, AEG Bulletin.

BS and MS Geological Engineering

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