Construction of Stabilization Works
The format and content of specifications for work to be contracted are usually
dictated by organizational policy, with only the technical details left to the engineer's
discretion. If that is not the case, then specifications can be developed by obtaining guide
specifications, or specifications for a particular project similar to the one being designed, from
an agency or firm accustomed to doing similar work in the region.
The following approach to bid items will expedite contract administration:
Use lump sum bid items for elements of the work for which (1) reliable
estimates of quantities can be prepared based on the advertisement for the
work, and (2) quantities are not likely to be affected by changed site
conditions, and (3) measurement and payment by unit price would be tedious.
Mobilization and demobilization are commonly done this way, but other items
such as site clearing, surface drainage work, and small items of excavation
(such as for dike bankheads) can also be effectively treated this way.
Use unit price bid items for work which may be significantly affected by
changed site conditions, and for which the actual quantities can be measured
easily. The unit of measurement should be the simplest one which is a reliable
indicator of work performed, such as ton of stone, area of vegetative
treatment, and linear measure of retard.
If more than one stabilization method or material would satisfactorily meet project
requirements, and the comparative cost of the alternatives cannot be reliably estimated
beforehand, then alternative bid items can be presented in the advertisement for bids, and the
contract can be awarded for the alternative with the lowest bid price. For example, if either
of two types of flexible mattress would be satisfactory, then the advertisement for bids could
provide for either or both to be bid on, and the contract would be awarded for the least
expensive one. This approach increases the design effort, since the specifications must
address all alternatives to be bid on. It is most likely to be feasible when other design factors,
such as geotechnical stabilization measures, beginning and ending points, and channel
alignment, would be identical with either alternative. A similar approach is commonly used
for vegetative treatment, with the date that the treatment is accomplished being the variable
which determines the type of treatment.
If the rate of supply of materials to the site is the controlling factor in the time
required to complete the work, then provision in the specifications to allow partial payment
to the contractor for stockpiled materials can be helpful in completing the work without delay.
This encourages the contractor to stockpile materials if that is required for timely completion,
although the capital costs involved will presumably be reflected by an increase in the bid price.
An alternative for speedy completion is to specify a compressed time allowance for
completion, with the contractor being penalized financially for exceeding that time, unless
unusual circumstances beyond the contractor's control were the cause. The risk in this
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