=124. Progress Reports.=[80]—These are kept by the engineer in order that he may see that the work is progressing as called for in the contract, and any portion which is lagging behind without reason may be pushed. Such reports are most useful when the information is expressed graphically, as the eye quickly catches points where the work is falling behind schedule. =125. Records.=—The contract drawings are supposed to show exactly where and how construction is to be done. Due to unexpected contingencies changes occur, of which a record should be made and preserved. These records may be kept in a form similar to the contract drawings, or if the changes are not extensive, they can be recorded on the original contract drawings. The location of house and other connections should be recorded in a separate note book available for immediate consultation. The engineer should keep a diary of the work in which are recorded events of ordinary routine as well as those of special interest and importance. This diary should be illustrated by photographs showing the condition of the streets before and after construction, methods of construction, accidents, etc. Such accounts are of great value in defending subsequent litigation and their existence sometimes prevents litigation. A contractor may wait a year or so after the completion of a piece of work until the engineer and other city officials have broken their connection with the city. Suit is then brought against the city and unless good records are available the administration may be forced to buy the claimant off or may elect to enter court, only to be beaten. [Illustration: FIG. 88.—Samples of Cost Record Forms. From Engineering and Contracting, 1909. ] Excavation =126. Specifications.=—The following abstracts have been taken from the specifications on Excavation by the Baltimore Sewerage Commission as illustrative of good practice. In conducting the work the contractor shall: ... remove all paving, or grub and clear the surface over the trench, whenever it may be necessary and shall remove all surface materials of whatever nature or kind. He shall properly classify the materials removed, separating them as required by the Engineer; and shall properly store, guard, and preserve such as may be required for future use in backfilling, surfacing, repaving or otherwise. All macadam material removed shall be separated and graded into such sizes as the Engineer may direct and materials of different sizes shall be kept separate from each other and from any and all other materials.