Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

Self-certification: the way ahead?

SELF-CERTIFICATION

Self-certification has proved its worth on CTRL, especially for earthworks, and is the way forward for geotechnical contracts, says Sharon Rose.

The CTRL contracts are based on the New Engineering Contract (NEC) with target costs and allow partnering and self-certification.

Contractor self-certification aims to demonstrate that specified requirements have been met.

The contractor has to ensure that all non-conformances or defects are reported and demonstrate to the project manager that they have been satisfactorily resolved.

The NEC does not have a role for the resident engineer. Instead, it uses the project manager, who does not supervise construction, but manages it. As a result, the designer does not necessarily become part of the contract team.

Ultimately, on a true self-certification contract, once design is finished, the contractor takes over and the designer takes a back seat.

The advantage of self-certification is that confrontational elements in construction are removed, allowing problems to be identified and rectified, while it is still possible to influence the outcome.

This form of contract should lead to less adversarial contracts and therefore less disputes.

However, the disadvantage of self-certification is that it relies on a wellskilled workforce, which is often not the case in construction. To ensure it is carried out satisfactorily, it is essential the contractor's personnel have adequate experience and knowledge and are fully aware of the designers' objectives and requirements.

On Contract 440, Ashford (town outskirts) to Cheriton, self-certification enabled classification of materials before they were used, easing planning and improving client confidence. Earthworks contractor CA Blackwell worked closely with main contractor Balfour Beatty Major Projects' on-site laboratory.

Non-conformance reports (NCR) were raised by the laboratory on materials failing to comply with the specification. The system allowed concessions to be requested where the contractor felt that, although the material may have failed to meet the specified criteria, the failure would not be detrimental to the final product. In the event, only nine NCRs were raised for Category 1 embankment fill on the contract.

RLE's Ground Engineering team is responsible for all earthworks specification on CTRL, with clear 'goal posts' and limits laid down. The timing and submission of test and inspection results is critical, as the 'product' rapidly gets buried and is then difficult to correct.

Tenderers were given factual ground investigation data; baseline monitoring water and gas data; contaminated land risk assessment reports; geotechnical summary reports; design notes for foundations and earthworks; and earthworks materials reports - including interpretation of each geological 'family' and acceptability assessment for each major cut.

As well as information such as foundation levels and anticipated ground and groundwater conditions, contractors' specification includes acceptance criteria, the number of acceptance tests and equipment to be used, any actions in the event of partial or total test failure and who to report results to. However, it must be noted that self-certification is virtually impossible in some ground conditions.

Contractor materials testing works reasonably well because this has been the trend for several years. Method compaction was carried out with rollers fitted with tachometers and using the French 'Q/S' method, which produces good self-certification records. RLE provides proforma for contractors.

All 4M. m 3of railway embankment fill was compacted to an end product specification requiring a large amount of testing.

Compliance criteria were less than 10% air voids for chalk fill (DoT Class 3) and greater than 95% of target dry density (Heavy Proctor) for uniform sands (DoT Class 1B).

So, is this the way forward for heavy civils work in the UK or a very naive alternative? Will the client end up paying many times over in the future for reduced quality resulting from contractor self-certification?

Self-certification has been successfully used in the automobile industry for many years. As a result, it has shown an increase in efficiency and a transformation which a decade or more ago, nobody would have believed possible.

This is why the Latham Report considers the automobile industry an example of what the construction industry should be able to achieve through selfcertification.

However, the question remains:

Can geotechnics be truly compared to the automobile industry?

Some may argue that in geotechnics, every design - and therefore product - is unique.

But there are comparisons with geotechnics and manufacturing.

Many geotechnical solutions are essentially repeat processes that can be continually improved but, more importantly, the process of design and construction is itself repeated from project to project.

Research suggests that up to 80% of input into design and construction are repeated. The parallel is not with building cars on the production line - it is with designing and planning the production of a new car. Nonetheless, even with its problems, geotechnical engineers can only learn to refine design by feeding back the observations and testing carried out during construction.

Sharon Rose is RLE geotechnical engineer.

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.