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Estimating Field Conditions C a

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ESTIMATING FIELD CONDITIONS C A. The estimator will generally have trouble when it comes to the amount of work to be done, this usually being roughly approxi mated, with the right to increase or decrease it later. A good method is to write down the maxi mum and minimum amounts that are likely to be involved. Clauses in the contract which en able the owner to change the contractor's quan tities without changing unit-prices, should add something to the contractor's estimate, for the reason that there is one best plant, one best ar rangement, one best organization, and one best outfit for every particular work. It has been shown that many of the conditions which affect the economy of the work are themselves affected by the quantities of work to be done; and any change on the part of the owner's mind affecting the quantity of work to be done, should—but rarely does—tend to increase or decrease the contractor's unit-price. In order to guard against such a contingency, the contractor should add something to his price by way of Insurance. After an estimate has been made, it is a practice of many contractors to "unbal ance" their bids. A great danger from this is that the work may have to be completed with quantities different from what were originally figured. • C Ek and C Ec. The kind and condition of the equipment available should be at hand, but is not often turned over to the estimator, unless he asks for it.

C F.

Frequently the name of the man who is going to superintend the work is not known in advance, and it should be established if possible.

C G.

The general layout of the work can be determined only by a personal inspection of the ground; and on this the estimator should make copious notes, having special reference to the distance of railroad connections, the distance of the railroad connection from shipping points of materials and supplies, the character of the country, the kind of water, and as many of the local conditions as can be reasonably and quickly noted.

C H.

He will find that the time for com pleting the contract will be usually determined by the business conditions. This ought to be ascertained with considerable care, because upon it depends the scale of the work.


of the Labor Market. It is diffi cult to predict this two or three years in advance.

In unfamiliar territory, if the Padrone system is in use in the neighborhood, it is not difficult to obtain from the nearest Padrone an estimate of how many men he can furnish, and then, by cut ting the estimate in two, get somewhere near the probabilities. If it is necessary to board or transport the men, a provision for this should be made in the estimate.


of Material. This is perhaps the most important item, and is the hardest to establish, because of the expense attendant upon the digging of test borings, making bor ings, etc. Personal inspection, where a man has had considerable experience, will go a long way toward helping out; but in earth and rock work a certain amount of boring is absolutely neces sary for proper results.

C .

Management. The method of manag ing should be understood before the estimate is to be made. If upon the work a bonus system and cost analysis are to be used, prices can be materially lower than when the ordinary day labor method is to be employed. Just how much lower, is a matter of judgment; but from past experience it may be safely said to be some 10 to 40 per cent—with 20 per cent as a safe average on general work.

C P.

If electric power is available, the fact should be carefully noted.

C S.

The kind of supplies readily available, and their cost on the work, should be estimated, not neglecting the water problem. The cost of coal of good quality will vary a great deal; and if a poor quality has got to be used, a very much larger amount should be allowed for than if the quality were good.

C T. It

is well to put this item (tools) in the estimate, as the estimator is more likely to know the proper kind and size of tools than the pur chasing agent, and it serves as a useful reminder. Shovels of the proper size may not be locally purchasable on short notice.

C V. Whether or not to work night shift, can be determined by estimating the necessary daily output to complete the work in time; and if this daily output cannot be safely reached with the labor available by day, night shift must be figured on. If one night shift is to be employed, from 7 to 10 per cent should be added to the labor cost; while, if two night shifts are to be put on, 10 to 12 per cent of the unit labor cost should be added, since the output per man working night shift is likely to be from 15 to 20 per cent less than by day. Of course, judgment must be used here, depending upon the kind of work, conditions, etc. Night shifting in summer is a much simpler matter than in winter.

C W. The weather is the greatest control ling factor, excepting in tunneling and on the interior parts of building to be done after the roof is on; and the probable number of working days on a short job cannot be estimated, except at considerable risk. Therefore, when the job is small, the unit-prices have to be assumed higher on this account than when the work is of long duration and the average weather counted on. When the work is to be done in an un familiar climate in the United States, the rec ords of the Weather Bureau can be consulted, either by personal inspection or by writing to the Observer; and from these records the prob able number of rainy days and days of excessive frost can be quite closely estimated if the work is to be of long duration. This should always be done as carefully as possible, since the weather is economically one of the most important field conditions to be considered.

A working day is a day, not a holiday, suit able for work. If the day is not a holiday, and is suitable for a working day, whether work is done or not, that day is a working day.