PART I
SPECIFICATIONS FOR STREET ROADWAY PAVEMENTS
INTRODUCTORY
In addition to their value as memoranda and aids in preparing specifications for a particular project, carefully prepared general specifications, embodying the latest approved practice, sometimes supply the most useful and acceptable brief treatises upon any particular branch of engineering work. It has been partly with this thought in mind that the following set of specifications for standard street pavements has been prepared and is now offered to city engineers and municipal authorities.
To widen their range and increase their usefulness, copious foot notes have been added, referring to alternative requirements and methods of construction, and giving some of the reasons for the preference or adoption of the construction called for in the specifications. It is recognized that in a good many matters of detail embraced in these specifications there is difference of opinion among able engineers, many of whom are at least as competent as the writer to determine what is best. They are not offered in a dogmatic spirit, or with the hope that all the provisions found therein will be accepted. If they shall be of some assistance in bringing about correct standards for such specifications, their preparation will have been justified.
Theoretically, three general classes of engineering specifications may be noted. In the first, the aim of the engineer is to specify the end or result that it is desired to secure, leaving the contractor free to originate and follow the methods by which these results are to be attained. In the second the engineer aims to secure the desired end by specifying in detail the materials and the methods which in his opinion will accomplish the purpose, he himself assuming responsibility for the results. Either of these two classes of specifications is permissible, and the engineer may choose the one which in his opinion seems best adapted to the character of the work to be done, and the conditions under which it must be prosecuted.
In the third class of specifications, met with more frequently than they should be, the engineer undertakes to prescribe not only the character of the materials to be used and the methods to be pursued, but also the results to be attained. The position thus assumed is illogical, and often unreasonable, and may lead to complications between the engineer and the contractor. If a contractor be required to turn out a product which shall conform to certain standards, he may properly be given much, if not full latitude, as to how the stipulated results shall be secured, and may be held fully responsible for the outcome; if on the other hand the engineer chooses to specify with more or less minuteness the character of the materials to be used and the methods of construction to be followed, and enforces compliance therewith, it seems fair and just that he should assume responsibility for the results produced, and therefore unfair to hold the contractor to responsibility for consequences arising from the use of materials and methods which he was allowed no choice or latitude in selecting.
In street paving work, of well-known and standard character, the second class of specifications seems preferable for a number of reasons, the leading one being that the time required to develop the good or bad quality of the work must usually extend over a considerable number of years, and the conditions to which the pavement may be subjected in the meantime are likely to vary so widely that it may be very difficult, if not impossible, to prescribe a satisfactory standard of service and endurance. Disputes are therefore liable to arise between the municipality and the contractor as to the latter’s liability, or conditions may make it difficult or impossible to hold the contractor to strict account for that liability.
It is believed that in the present state of the art it is entirely practicable to so frame specifications for the materials to be used and the methods to be followed in the construction of standard street pavements, and to so enforce compliance therewith, that the engineer and the municipality may safely assume responsibility for the quality of the work produced. While it may be true that local conditions sometimes make it very difficult to enforce compliance with specifications, the same conditions are likely to make it at least equally difficult to secure effective responsibility on the part of the contractor for any long-period guarantee of the work done by him; and the contractor who negligently or purposely violates the specifications during construction is not likely to be more faithful or scrupulous in living up to any guarantees he may make with regard to the future, even where the terms and conditions of such guarantees may be clearly defined and indisputable. The writer has discussed the subject of time guarantees as applied to street pavements pretty fully in his book, “Municipal Public Works,” and the above brief statement seems all that is necessary here.
In conformity with this view of the matter, the following specifications aim to set out as definitely and clearly as practicable the requirements for the construction of good pavements of the several standard kinds, and it is assumed that the engineer will be able to, and will enforce them.
It is, however, not infrequently the case that the engineer will be called upon to prepare specifications for new, or patented, or proprietary pavements advocated by their promoters, the value or usefulness of which have not been sufficiently established by experience, and for which the data for detailed, definite specifications are not yet available.