Additional works–Retaining wall with soil nailing works

In one of the Road projects in Dubai, one additional works were instructed to the Contractor. This instruction was given as per the details shown on the Contract drawings but the work details were not provided or considered in the total Contract. A single line outline wording was given in the Contract Drawings showing that a “retaining wall is to be constructed” while extending the road underneath the Bridge. This Retaining wall is to be constructed just below the below existing bridge and very near to the bridge abutment foundation.

There was already an existing stone pitching available with larger slope. Works involved to do the above varied works were

a) Firstly, remove the existing stone pitching works – this item was also not in the Bill of Quantities

b) Testing the soil stability – Third party testing is to be carried out with the specialists – additional cost to the Contract. Engineer instructed the Contractor to carry out the job.

c) Soil nailing method: Recommended soil stabilization method by the Specialist to stabilizing the existing sloped soil portion underneath the bridge at the abutment portion without disturbing the existing structure foundation.

d) Retaining construction: New retaining wall to be constructed for about 80m length with “L” shape foundation. In front of the Retaining wall, Concrete barrier to be installed/constructed. Temporary works related to do this job was huge. Existing traffic maintenance and protection to the works area with kentledge blocks, more safety features etc., involving additional cost to the Contractor.

e) Road works: existing two lane road to be extended nearer to the retaining wall portion.

Items “a & e” could be covered under the existing BOQ items as additional quantities. Items “b,c & d” would become variation to the Contract.

Discussion:-

Engineer was under impression that Contractor must study the drawings and quote the works’ rates accordingly. No additional cost for the items “b & c” should be considered for payment because they are the part of the temporary protection measures while doing the permanent works (Retaining wall). Though the structural details of the Retaining wall was not in the original tender drawings, Engineer had provided the drawings during the construction stage for execution to the Contractor. Engineer’s contention was that Tender drawings were showing the Retaining wall location, though the structural details and Bill of quantities were missed out, it would be the Contractor’s obligation to execute the job provided in the Contract. (Note: Only a single line sentence “Retaining wall is to be constructed” was given on the Contract drawings)

Contractor argues that the Contract value and provided Bill of quantities did not contain the Retaining wall cost. And also, the Contract/Tender drawings did not show any specific structural drawing details. Hence, the works instructed during the construction stage would become a variation to the Contract and subsequent permanent and temporary specialist treatment arrangements’ cost should be payable to the Contractor. Measurements shall be payable as per actual as per re-measurable Contract.

Conclusion:-

Engineer agreed to pay the Permanent works cost and also the soil nailing method (special treatment to stabilize the soil) cost to the Contractor. Since, these work details were not provided to the Contractor at the Tender stage, though the Contractor had not raised this issue at the Pre-bid meeting stage nor any other competitor at that stage. Hence, additional cost due to specialist treatment which could not be foreseen by any experienced Contractor and the retaining wall works with finishing works (details provided during the construction stage) cost considered for payment to the Contractor.

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Curved and sloping soffit item in Bridge Deck formwork

In one of the Road projects in Dubai, the following Bill of Quantities are available in a re-measurable Contract.

Formwork measurement for Bridge Deck (measurable unit is Square Metre)

a) Horizontal Soffit; 

b) Curved and sloping soffit

c) Edges of Bridge deck

There is a dispute in measuring the Curved and sloping soffit item.

Contract Preamble says “The formwork of bridge deck, plane sloping and curved surfaces shall not be measured separately but they are deemed to be included in the BOQ item “Curved and sloping soffit”

But as per CESMM3 plane sloping criteria is

Horizontal          90 deg to 85 deg

Sloping              85 deg to 10 deg

Batter                 10 deg to 0 deg

Vertical               0 deg.

 

But Bridge Deck is having total three BOQ items (as mentioned above) for measuring the formwork.

Consultant wants to measure the Cantilever portion of the Bridge Deck in the Horizontal soffit item wherever the angle is in between 0 degree to 5 degree to the true Horizontal and rest of the portions of the box girder of the bridge deck formwork in other respective items.

Ambiguity:

a) Why the preamble condition is given and not implementable in a practical manner?

b) Why the provided BOQ item quantities are covered in only above 3 items and why the entire bridge deck cantilever formwork quantity is considered in the “Curved and sloping soffit item?

c) While entering the Contract, why the Contractor has not asked the this question regarding the formwork payable items? because Bridge deck is a composite suspended concrete structure and any change in the Horizontal alignment will result on both cantilever portions and horizontal portions as well. Construction point of view, cantilever portion formwork is more difficult than the normal horizontal soffit. Whether the preamble condition has misled the Contractors?

d) When the preamble says that plane sloping and curved portions are not measured separately, then why the Consultant wants to divide the both side cantilever portions into two separate entities.

Cost point of view, Contractor has to incur more cost in the preparation of the curved and sloping soffit item than the horizontal soffit item and Contractor has considered his item cost and quoted as per the given BOQ only.

Another point is, even Consultant has given the BOQ quantities distribution by considering the (both side) cantilever portion formwork quantity in the Curved and sloping soffit item only, but not in the horizontal soffit item. Contractor’s CANDY (costing) workout of the item rate also shows that cantilever formwork cost is considered in the Curved and sloping soffit item only. Hence, there should not be any ambiguity in measuring the above item in the given BOQ item (b).

Conclusion:

As per the work point of you, preparation and fixing of formwork for the curved and cantilever portion is a single unit construction. Cantilever slope is the continuation of the curved portion of the bridge deck web. Preamble and BOQ item quantities are giving clear cut hint about the measurement criteria and provision. As per my view, by considering the above two hints in the Contract and also the construction complexity at the cantilever portions, both side cantilever’s formwork areas are to be measured and paid under the BOQ item “Curved and sloping soffit” only.

Thanks

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