There are, however, a number of matters of fact in reference to which it is proper and necessary to make the judgment and decision of the engineer controlling and final, unless it may be shown that his decision is clearly erroneous or affected by improper motives, or by fraud. Some one must necessarily be made the immediate and final judge as to whether the quality of materials and workmanship is in accordance with the requirements of the plans and specifications, and as to the quantity of work actually performed, and these duties and responsibilities are very properly placed upon the engineer.
It not infrequently occurs that specifications are not drawn as clearly as they should be in the matters of methods of measuring the work and of applying contract unit prices, and indefiniteness and carelessness in this regard are often a source of misunderstanding and dispute between the engineer and the contractor. It is a good practice, followed by many able engineers, after specifying how a certain part of the work shall be done, to state how it shall be measured and paid for at the contract unit prices.
In many respects it is desirable that all the work to be done under contract should be quite fully itemized, and a unit price named for each kind of work. It is the custom in many cities to name only certain leading items of the work to be done under a paving contract, as for the pavement complete, furnishing and setting new curbing, redressing and resetting old curbing, and possibly a few other leading items, and to require that all necessary incidental work shall be done by the contractor without cost to the city; or, in other words, he must take this possible extra work into consideration in naming his unit prices for the leading items of the work. As the quantity of this incidental work is often not stated, and the contractor has no means of ascertaining it, he must guess, as intelligently as he may be able, how much he should add to his unit prices to cover its cost. If he is a prudent contractor he will be sure to add enough to prevent any possible loss on this account. In most cases the quantities of this incidental work can be determined and scheduled by the engineer with the more important items, and the contractor may be required to name unit prices for it. True, there are likely to develop during the progress of the work some items that could not be foreseen or that were overlooked. In some cities such contingencies are provided for by a clause in the contract or specifications scheduling, by name, all the incidental minor items of work that experience has shown are likely to be met with in street paving contracts, and naming fair unit prices which the contractor will be paid for each, should it occur. The contractor may then feel assured that however much the quantity of such incidental work may vary, he will receive compensation proportionate thereto, and he may name his prices for the main items with more confidence. Under such conditions it is reasonable to expect closer figures than he would be willing to name if an unknown quantity of incidental work for which no separate pay is provided had to be taken into consideration.
Sub-division of unit prices is also desirable in order that the engineer may be able to analyze and record the elements that make up the aggregate cost of the work. Thus, in the case of the construction of a new sheet asphalt pavement it is common to ask for a single price for the pavement complete, including a five year guarantee. Now the work will consist of several distinct operations or kinds of work for each of which a separate price might be named:
1. The grading of the street and preparation of the sub-grade. The quantity of this work will vary on different streets and is best reckoned by the cubic yard of material excavated.
2. A price, either per cubic yard or per square yard for the concrete foundation.
3. A price per square yard for the asphalt pavement proper. This might, if desired, be sub-divided into separate prices for the base-course and the surface-course.
4. A price per square yard for guaranteeing the pavement for five years.
Such sub-division would, it is true, increase the work of final computation but if of no other value, the detailed costs would be a great aid to the engineer in estimating the reasonable cost of future work where the relative quantity of these detailed parts varied.